Chapter 13 Viruses, Chapter 5 Microbiology 2500, Chapter 4 Microbiology 2500, Micro 8 Microbial Genetics, Micro 6 Microbial Growth
In which phase of the growth curve is the population-doubling time fastest?
log phase
Which of the following is NOT a chemical requirement of all bacteria?
molecular oxygen
Which of the following is related to the lysogenic cycle?
prophage
Nitrogen is needed for
protein and nucleic acid synthesis
Which of the following is used to make ribosomes?
rRNA
Obligate aerobes+
require oxygen
Playmolysis
shrinkage of the cell's cytoplasm
A mutation that affects the genotype of the organism but not the phenotype is called a
silent mutation.
Base pair substitutions can result in what type(s) of mutation?
silent, nonsense, and missense
During which phase of growth would you find the highest number of total cells, both living and dead? lag phase log phase stationary phase death phase
stationary phase
The anticodon sequence is found on the __________.
tRNA
Binary fission results in
the production of two genetically identical daughter cells.
Genetics
the study of genes, how they carry information, how information is expressed, and how genes are replicated
Genomics
the study of genomes
The optimum growth temperature is
the temperature at which it grows best
Which of the following would be an example of horizontal gene transfer?
the transfer of DNA from one bacterium to another
Induction is?
the trigger of prophage excision from the host chromosome.
logarithmic progression
the way bacterial cell division occurs (2, 4, 8)
The role of transcription is ___________________.
to copy the information stored in DNA into RNA.
What is the function of the enzyme reverse transcriptase?
to make DNA copies of the RNA virus of retroviruses
What is the purpose of bacterial conjugation?
to transfer DNA between two living cells
aerotolerant anaerobes
tolerate but cannot use oxygen
Which of the following is NOT a type of horizontal gene transformation transduction conjugation transcription
transcription
Oncogenes
transform normal cells into cancerous cells
Anaerobes
unable to use oxygen and most are harmed by it
bacteriophages (phages)
viruses that infect bacteria
Discuss the relationship between DNA- and RNA-containing viruses and cancer.
~ 10% of cancers are caused by viruses. Several DNA viruses are retroviruses and oncogenic. The genetic material of oncogenic viruses become integrated into the host cells DNA. DNA viruses include HPV and Hep. B. The RNA viruses only the retroviruses seem to oncogenic. HTLV-1&2 have been found to cause cancer. Activated oncogenes transform normal cells into cancerous cells Transformed cells have increased growth, loss of contact inhibition, tumor-specific transplant antigens, and T antigens The genetic material of oncogenic viruses becomes integrated into the host cell's DNA
The Size, Shape, and Arrangement of Bacterial Cells
•Average size: 0.2 to 2.0 μm diameter × 2 to 8 μm length •Most bacteria are monomorphic (single shape) •A few are pleomorphic (many shapes)
The Size, Shape, and Arrangement of Bacterial Cells
•Bacillus (rod-shaped) •Coccus (spherical-shaped) •Spiral -Vibrio -Spirillum -Spirochete •Star-shaped Rectangular
types of plasmids
•Conjugative plasmid: carries genes for sex pili and transfer of the plasmid •Dissimilation plasmids: encode enzymes for the catabolism of unusual compounds •Resistance factors (R factors): encode antibiotic resistance
plasmids and transposons
•Mobile genetic elements -Move from one chromosome to another or from one cell to another •Occur in prokaryotic and eukaryotic organisms
Cytoplasmic (Plamsa) Membrane (Prokaryote)
•Phospholipid bilayer that encloses the cytoplasm •Peripheral proteins on the membrane surface •Integral and transmembrane proteins penetrate the membrane Structure- Fluid mosaic model -Membrane is as viscous as olive oil -Proteins move freely for various functions -Phospholipids rotate and move laterally -Self-sealing
Flagella and Cilia of Eukaryotic Cells
•Projections used for locomotion or moving substances along the cell surface •Flagella—long projections; few in number •Cilia—short projections; numerous •Both consist of microtubules made of the protein tubulin •Microtubules are organized as 9 pairs in a ring, plus 2 microtubules in the center (9 + 2 array) •Allow flagella to move in a wavelike manner
Fermentation
•Releases energy from the oxidation of organic molecules •Does not require oxygen •Does not use the Krebs cycle or ETC •Uses an organic molecule as the final electron acceptor •Produces only small amounts of ATP •Lactic acid fermentation: produces lactic acid -Homolactic fermentation: produces lactic acid only -Heterolactic fermentation: produces lactic acid and other compounds •Glucose is oxidized to pyruvic acid, which is then reduced by NADH •Alcohol fermentation: produces ethanol + CO2 •Glucose is oxidized to pyruvic acid; pyruvic acid is converted to acetaldehyde and CO2; NADH reduces acetaldehyde to ethanol
RNA and protein synthesis
•Ribonucleic acid - Single-stranded nucleotide - 5-carbon ribose sugar Contains uracil (U) instead of thymine (T) •Ribosomal RNA (rRNA): integral part of ribosomes •Transfer RNA (tRNA): transports amino acids during protein synthesis •Messenger RNA (mRNA): carries coded information from DNA to ribosomes
ribosomes in prokaryotes
•Sites of protein synthesis •Made of protein and ribosomal RNA •70S -50S + 30S subunits Free: in cytoplasm
Enzymes and Chemical Reactions
•Substrate contacts the enzyme's active site to form an enzyme-substrate complex •Substrate is transformed and rearranged into products, which are released from the enzyme •Enzyme is unchanged and can react with other substrates
Aerobic Respiration
•The final electron acceptor in the electron transport chain is molecular oxygen ( O2)
Functions of Cell Wall (Prokaryote)
•The plasma membrane's selective permeability allows the passage of some molecules, but not others •Contain enzymes for ATP production •Some membranes have photosynthetic pigments on foldings called chromatophores
Gram Negative Cell Wall (Prokaryote)
•Thin peptidoglycan •Outer membrane •Periplasmic space •Periplasm between the outer membrane and the plasma membrane contains peptidoglycan •Outer membrane made of polysaccharides, lipoproteins, and phospholipids •Protect from phagocytes, complement, and antibiotics •Made of lipopolysaccharide (LPS) -O polysaccharide functions as antigen (e.g., E. coli O157:H7) -Lipid A is an endotoxin embedded in the top layer •Porins (proteins) form channels through membrane
Describe how bacteriophages are cultured
•Viruses must be grown in living cells •Bacteriophages are grown in bacteria -Bacteriophages form plaques, which are clearings on a lawn of bacteria on the surface of agar §Each plaque corresponds to a single virus; can be expressed as plaque-forming units (PFU)
Plasmids
•are self-replicating circular pieces of DNA •1 to 5% the size of a bacterial chromosome •Often code for proteins that enhance the pathogenicity of a bacterium
singlet oxygen
(1O2-) boosted to a higher-energy state and is reactive
Bacterial growth curves typically can be divided into four distinct phases: lag phase, log phase, stationary phase, and death phase.
(Left to right) Log of the number of bacteria, Bacteria are metabolically very active, but the numbers are not increasing, Period of most rapid growth. Number of bacteria is increasing exponentially, Time, Population growth has halted. Number of new cells formed balances the number of cells dying, Rate of the cell death exceeds the rate at which new cells are being formed. Numbers of cells decline exponentially
Hypertonic
(of a solution) having a higher osmotic pressure than a comparison solution
Hypotonic
(of a solution) having a lower osmotic pressure than a comparison solution
Which of the following viral genomes can be used directly as messenger RNA?
+RNA
Vacuoles (Eukaryotes)
-Cavities in the cell formed from the Golgi complex -Bring food into cells; provide shape and storage
lytic cycle steps
-Phage causes lysis and death of the host cell 1. attachment 2. penetration 3. replication 4. assembly 5. lysis
Place the following events of lagging strand DNA synthesis in order:
1. Primase adds an RNA primer. 2. DNA polymerase synthesizes new DNA strand in the 5' to 3' direction. 3. RNAse removes the RNA primer. 4. Okazaki fragments are joined together.
If a single bacterium replicated every 30 minutes, how many bacteria would be present in 2 hours?
16
The Generation of ATP
ATP is generated by the phosphorylation of ADP with the input of energy
Define and explain the importance of catalase.
Catalyzes the breakdown oh H2O2 to O2 and H2O.
Provide an example of a latent viral infection
Cold sores, shingles
Central Dogma
DNA -> RNA -> Protein
Which of the following DNA sequence best represents a mutation of this sequence: 5' - TACGTAGCA - 3'?
DNA: 5' - TACCTAGCA - 3'
Which selective and differential medium is used to identify Staphylococcus aureus ?
Mannitol Salt Agar
__________ viruses are released by accumulating in high numbers in the host cell until the cell lyses.
Naked
How does the ribosome know if the entering charged tRNA is correct?
The anticodon on the tRNA base pairs to the codon on the mRNA.
What is the initial target of RNA polymerase?
The promoter
Why do S strains escape killing by host phagocytes?
They are encapsulated.
Genome
all the genetic information in a cell
A prokaryotic cell hitched a ride to Earth on a space shuttle from some unknown planet. The organism is a psychrophile, an obligate halophile, and an obligate aerobe. Based on the characteristics of the microbe, describe the planet.
cold, salty, aerobic.
transducing phage
contains fragments of the host chromosome instead of the viral genome.
sense codons
encode the 20 amino acids
binary fission
A form of asexual reproduction in which one cell divides to form two identical cells.
Budding
A form of asexual reproduction of yeast in which a new cell grows out of the body of a parent.
Explain the importance of osmotic pressure to microbial growth
A hypertonic enviroment, or an increase in salt or sugar cause plasmolysis. Microbes need a certain osmotic pressure to maintain integrity and get nutrients.
What kind of bond is formed when two amino acids join together?
A peptide bond
What is the order of ribosomal sites that a charged tRNA molecule passes through?
A site P site E site
A bacterial strain undergoes a chromosomal mutation that converts one of its genes to a resistance gene. Later, you discover that some members of this strain now carry the gene on a plasmid. Which of the following do you think accomplished this transfer?
A transposase
Why could it be argued that a virus is not alive?
A virus requires a host cell in order to reproduce.
Which statement about conjugation is true?
After conjugation, each cell involved has a copy of the shared DNA.
Which of the following statements is true?
All viruses follow the same general life cycle.
What Happens in Each Step of the Viral Replication Process for a DNA-containing Virus?
Attachment: requires a physical and chemical interaction between the surface of the virus and host cell surface Entry and uncoating: -this process disassembles the viral capsid and releases the viral DNA -may involve fusion of the viral envelope with the host cell plasma membrane -may involve receptor-mediated endocytosis Biosynthesis: -Transcription of viral genes by host cell RNA polymerase occurs during this stage -New copies of viral DNA genomes are made during this stage -Translation of viral capsid proteins and other viral proteins occurs during this stage -The viral DNA must enter the host cell nucleus prior to this stage Maturation: -Capsids are assembled from capsomeres -Viral genomic DNA is packed into newly assembled capsids Release: -Nonenveloped viruses often lyse the cell during this process -Enveloped viruses accomplish this via a budding process
Animal Viruses Steps
Attachment: viruses attach to the cell membrane Entry by receptor(penetrating)-mediated endocytosis or fusion Uncoating by viral or host enzymes Biosynthesis: production of nucleic acid and proteins Maturation: nucleic acid and capsid proteins assemble Release by budding (enveloped viruses) or rupture
chemical mutagens
Chemicals that cause genetic mutations •Nitrous acid: causes adenine to bind with cytosine instead of thymine •Nucleoside analog: incorporates into DNA in place of a normal base; causes mistakes in base pairing
A chemostat is continuous culture system that is designed to promote and prolong exponential growth and prevent bacteria from entering stationary phase. How might this work?
Chemostats provide a continued source of fresh nutrients and remove wastes and dead bacterial cells.
Viral Multiplication
For a virus to multiply: It must invade a host cell It must take over the host's metabolic machinery One-step growth curve
DNA synthesis occurs in which direction?
From 5' to 3' on both the leading and lagging strands.
What would you expect to observe when a halophile that cannot ferment mannitol is cultured on mannitol salts agar?
Good growth accompanied by no change in color of the medium.
You are working in a research lab trying to determine which mixtures of bacterial species can form biofilms. To determine this, you perform a bacterial growth study looking at the number of viable bacteria cells remaining after treatment with penicillin (an antibiotic). You know that all your mixtures of bacteria are susceptible to penicillin when they do not grow as a biofilm. You include a control mixture in your study that you know does not form biofilms. Three different experimental mixtures (Groups 1, 2, and 3) and your control were grown at the same density of cells (12,000 cells per dish). You treat all groups with the same dose of penicillin for 10 hours. You count the number of viable cells 6 hours and 48 hours after the treatment ends. The graph below shows the data from this experiment. Group 1 Group 2 Group 3 Groups 1 and 2
Group 2
Psychrotrophs
Grow between 0°C and 20-30°C Cause food spoilage
Why might primitive civilizations have used food preservation techniques that rely on osmotic pressure?
Growth of the cell is inhibited as the plasma membrane pulls away from the cell wall. The high salt or sugar concentrations draw water out of any microbial cells, thus prevent their growth.
The reaction that is carried out by the enzyme catalase produces __________.
H2O and O2
Define and explain the importance of hydrogen peroxide.
H2O2; perioxide ion is O2^2-
How does and F+ cell differ from an Hfr cell?
Hfr strains have the F plasmid integrated into the chromosome
A. baumannii became resistant to tetracycline by acquiring an R plasmid. Which of the following best describes how A. baumannii obtained this R plasmid?
Horizontal gene transfer
Which of the following terms are mismatched?Hyperthermophiles; 0°C Acidophiles; low pH Extreme thermophiles; 100°C Extreme halophiles; 30% salt Psychrophiles; 0°C
Hyperthermophiles; 0°C
Name a use for nitrogen needed in large amounts for microbial growth.
In amino acids and proteins, some bacteria use NH4 or NO3, few bacteria use N2 in nitrogen fixation, synthesis of DNA and RNA, synthesis of ATP
Which of the following statements regarding latent viral infections is true?
Latent infections can persist for years in an individual without causing any symptoms.
Differentiate persistent viral infections from latent viral infections.
Latent virus Remains in asymptomatic host cell for long periods May reactivate due to changes in immunity Persistent viral infection Occurs gradually over a long period; is generally fatal -Subacute sclerosing panencephalitis (measles virus)
Which of the following options is a signature symptom of necrotizing fasciitis?
Loss of tissue around a wound
Microbes have very narrow optimum temperature ranges. Which of the following classifications of microbes are most likely to cause human disease, based on their temperature requirements? hyperthermophiles thermophiles mesophiles psychrophiles
Mesophiles - The temperature range of mesophiles overlaps that of normal human body temperature, allowing the greatest growth.
base substitution mutation can be divided into 3 other types
Missense mutation Nonsense mutation Silent mutations
Identify how and why the pH of culture media is controlled.
Most bacteria grow between pH 6.5 and 7.5.
Describe the effect of mutagens on the mutation rate.
Mutagen is an agent in the environment that brings about mutation. If a mutagen is present, it will usually increase the spontaneous rate of mutation, which is approximately 1 in 106 replicated genes, by a factor of 10-1000 times. This is a 1 to 3 order of magnitude increase, meaning a mutation rate of 10-6 becomes 10-5 or possibly 10-3.
How do normal prion proteins (PrP) differ from the infectious prion proteins?
Normal PrP have alpha-helices; infectious PrP have beta-pleated sheets
Which of the following types of macromolecules are found in all viruses? Select all that apply. Nucleic acids Lipids Proteins Polysaccharides
Nucleic acids and Proteins All viruses have a protein coat, called a capsid, which surrounds some type of nucleic acid, either DNA or RNA. Some viruses also acquire a lipid bilayer envelope as they exit from the host cell.
A pastry chef accidentally innoculated a pie with six S.aureus cells. If S. aureus has a generation time of 60 minutes, how many cells would be in the pie after 7 hours?
Number of cells x 2^n generations = Total number of cells6 x 2^7 = 768
superoxide radicals
O2
peroxide anion
O2 2-
Define and explain the importance of superoxide radical.
O2-; This anion has one unpaired electron.
Explain how microbes are classified on the basis of oxygen requirements.
OBLIGATE AEROBESs: oxygen required FACULTATIVE ANAEROBESs: both aerobic and anaerobic growth, greater growth in the presence of oxygen OBLIGATE ANAEROBES: only anaerobic growth, ceases in the presence of oxygen AEROTOLERANT ANAEROBES: only anaerobic growth, but continues in the presence of oxygen MICROAEROPHILES: only aerobic growth, oxygen required in low concentration
hydroxyl radical
OH-
General Characteristics of Viruses
Obligatory intracellular parasites Require living host cells to multiply Contain DNA or RNA Contain a protein coat No ribosomes No ATP-generating mechanism
What is considered to be the average natural mutation rate that occurs during DNA replication?
One in every billion nucleotides replicated.
How frequently do silent mutations occur?
One out of every three mutations
organic growth factors
Organic compounds obtained from the environment Vitamins, amino acids, purines, and pyrimidines
During the initiation step of translation, the fMet charged tRNA assembles in which site of the ribosome?
P site
Nitrogen and Phosphorus added to beaches following an oil spill encourage the growth of natural oil-degrading bacteria. Explain why the bacteria do not grow if nitrogen and phosphorus are not added.
Petroleum can meet the carbon and energy requirements for an oil-degrading bacterium; however, nitrogen and phosphate are usually not available in large quantities. Nitrogen and phosphate are essential for making proteins, phospholipids, nucleic acids, and ATP.
lysogenic cycle steps
Phage DNA is incorporated in the host DNA -Phage conversion -Specialized transduction 1. attachment 2. penetration 3. integration 4. replication 5. assembly 6. lysis
Discuss how a protein can be infectious.
Prions are proteinaceous infectious particles and cause neurological diseases in humans and animals. Prion diseases are due to an altered protein. The cause can be a mutation in the normal gene for PrP (host glycoprotein) or contact with an altered protein prion proteins cause plaques and holes in neural tissue resulting in progressive loss of function and eventual death
How does the number of infectious prions increase?
Prions transform normal proteins into the misfolded beta-pleated sheet configuration; therefore, prions multiply by conversion.
How does protein-dependent termination differ from protein-independent termination?
Protein-dependent termination involves the use of a protein to end transcription.
From which phrase is the term "prions" derived?
Proteinaceous infectious particles
__________ organisms are often responsible for food spoilage in refrigerated foods.
Psychotroph
Statements regarding RNA polymerase.
Reads the template strand of DNA. Adds nucleotides to the 3' end of the growing RNA molecule. Binds to the promoter region of the gene prior to starting RNA synthesis.
Microbes in biofilms are more...
Resistant to antibiotics than are free-swimming microbes.
RNA oncogenic viruses
Retroviridae Viral RNA is transcribed to DNA (using reverse transcriptase), which can integrate into host DNA HTLV-1 and HTLV-2 cause adult T cell leukemia and lymphoma
What Are the Implications of the Attachment Process?
-A particular virus may be able to infect humans but not mice. -A particular virus may be able to infect a liver cell but not a lung cell. -Some people are naturally (innately) resistant to certain viral infections. -Viral infection of a cell may be prevented by blocking the attachment sites on a virus with antibody. -Viral infection of a cell may be prevented by blocking the receptor sites on a host cell.
frameshift mutation
-Insertion or deletion of one or more nucleotide pairs -Shifts the translational "reading frame"
Centrosomes (Eukaryotes)
-Networks of protein fibers and centrioles -Form the mitotic spindle; critical role in cell division
Hyperthermophiles
-Optimum growth temperature >80°C
Thermophiles
-Optimum growth temperature of 50° to 60°C -Found in hot springs and organic compost
Peroxisomes in eukaryotes
-Oxidize fatty acids; destroy hydrogen peroxide
Lysosomes (Eukaryotic)
-Vesicles formed in the Golgi complex -Contain digestive enzymes
How Can Antiviral Medications Selectively Interfere with Viral Infection Cycles? Select strategies that are likely to interfere with viral infection and replication but will NOT damage the normal functioning of host cells.
-blocking host cell receptors that serve as sites for viruses to attach -inhibiting viral assembly and maturation processes -inhibiting the release of viruses from the host cell -inhibiting viral-encoded DNA polymerase -encoded DNA polymerase-blocking attachment sites on the virus surface
DNA replication steps (only when cell is ready to split)
1) Helicase- unwinds the parental double helix 2) DNA topoisomerase - upstream of helices alleviating torsional strain 3) Single-strand binding proteins (SSBP) stabilize unwound DNA, aided by DNA gyrase. 4) Primase synthesizes a short RNA primer for DNA polymerase to bind to in the 5' to 3' direction to start replication on each strand. 5) DNA polymerase synthesizes the leading strand in 5' to 3' direction while the lagging strand is made discontinuously by primase making short pieces and then DNA polymerase extending these to make Okazaki fragments. 6) DNA ligase joins the Okazaki fragments together
Name a use for each of the four elements needed in large amounts for microbial growth
1) carbon: organic molecules 2) nitrogen: AAs to make proteins, DNA, ATP 3) phosphorus: ATP 4) sulfur: AAs
Describe the formation of biofilms and their potential for causing infection.
1) microbial communities that form slime or hydrogels that adhere to surfaces 2) can "clog pipes" or form on catheters, heart valves, contact lenses, dental caries
Identify ways in which aerobes avoid damage by toxic forms of oxygen
1) superoxide radical: formed during normal respiration, can form hydrogen peroxide - superoxide dismutase turns it into water and hydrogen peroxide 2) peroxide anion: can be formed from hydrogen peroxide - catalase turns it into water and oxygen
put the following events of conjugation in order: Transfer of the DNA Fusion of the cell membranes Pulling of donor and recipient cells together
1. Pulling of donor and recipient cells together 2. Fusion of the cell membranes 3. Transfer of the DNA
Translation steps
1. mRNA in cytoplasm binds to a ribosome (rRNA) 2. tRNAs anticodons bind to the codons on the mRNA sequence 3. the amino acids on the RNA bind to each other to form a long chain, or protein (in bacteria, translation can begin before transcription is complete)
Describe the process of DNA replication
1. the double helix of the parental DNA separates as weak hydrogen bonds between the nucleotides on opposite strands break in response to the action of replication enzymes 2. hydrogen bonds form between new complementary nucleotides and each strand of the parental template to form new base pairs 3. enzymes catalyze the formation of sugar-phosphate bonds between sequential nucleotides on each resulting daughter strand
Arrange the following steps in the order in which they occur during the reproductive cycle of the type of virus that causes the common cold.
1. using the cell's machinery to synthesize new viral proteins and nucleic acid. 2. attaching to receptors on the host cell. 3. releasing their nucleic acid from the capsid into the host cell. 4. releasing the new viruses from the host cell. 5. assembling new viruses
Transcription in Prokaryotes
1.Synthesis of a complementary mRNA strand from a DNA template 2.Transcription begins when RNA polymerase binds to the promoter sequence on DNA 3.Transcription proceeds in the 5' 3' direction; only one of the two DNA strands is transcribed 4.Transcription stops when it reaches the terminator sequence on DNA
Describe two ways mutations can be repaired.
1.photolyases-separate thymine dimers (use visible light energy to separate the dimer back to the original two thymines) UV induced damage 2.nucleotide excision repair- not restricted to UV damage, can repair mutations from other causes as well. enzymes cut out the incorrect base and fill int he gap with newly synthesized DNA that is complementary to the correct strand
Classify microbes into five groups on the basis of preferred temperature range.
1.psychrophiles: cold loving, -10 and 20C2) 2.psychrotrophs: cold tolerant, 0 to 30C, cause food spoilage3) 3.mesophiles: moderate temp loving, 10 to 50C4) 4.thermophiles: heat loving, 40 to 70C, found in hot springs5) 5.hyperthermophiles: greater than 80C
A broth medium has been inoculated, and microbial numbers will be counted periodically to generate a bacterial growth curve. At 2 hours after inoculation, the culture has progressed through lag phase and is now in log phase. At this point, the population size is 1 million cells. The generation time is 30 minutes. Assuming the continuation of log growth, how many cells would there be at 2 hours of growth in log phase?
16 million
In what year did Stanley Prusiner win the Nobel Prize for his discovery of prions?
1997, found in 1982
According to the chart, how many amino acids are coded for by codons?
20
If you begin with three cells, how many cells would you have after three rounds of division?
24
How many codons code for the termination of transcription?
3
Put the following steps of bacterial replication in order, starting from a parent cell. 1.Cell elongation 2.Septum formation 3.Chromosome replication 4.Separation of daughter cells
3, 1, 2, 4
During elongation, how is the RNA synthesized?
5' to 3'
If 52 bacterial colonies grow on a nutrient agar plate inoculated with 1 ml of a 1:1000 dilution of hamburger, how many bacteria are in the original hamburger sample? A. 52 bacteria per g B. 520 bacteria per g C. 5200 bacteria per g D. 52,000 bacteria per g
52,000 bacteria per g
Assume that you inoculated potato salad with 10 bacterial cells and stored it at room temperature. After 3 hours, there are 640 cells. How many generations did the cells go through?
6 generations
What temperature would most likely kill a mesophile?
60 degrees Celcius
Which of the following is NOT an example of horizontal gene transfer?
A bacterium passes a mutated gene to its offspring via binary fission
Why is binary fission more quick and efficient when compared to eukaryotic cell division?
Bacteria do not need to form a mitotic spindle nor dissolve a nuclear membrane.
Classify mutations by type.
Base substitution (point mutation) Frameshift mutation
nonsense mutation
Base substitution results in a nonsense (stop) codon
missense mutation
Base substitution results in change in an amino acid
Why is it useful to plot bacterial growth on a logarithmic graph?
Because the number of cells increases rapidly, a logarithmic graph allows you to visualize the complete growth curve.
This question asks you to make comparisons regarding the slope of an exponential growth curve, based on generation time. Each of the three graphs shown below includes data collected during exponential growth of a species of bacteria grown in three different growth conditions. Which growth condition resulted in the longest generation time?
C- line closes to x axis
Chemical requirements for growth
Carbon - Structural backbone of organic molecules Nitrogen - Component of proteins, DNA, and ATP Sulfur - Used in amino acids, thiamine, and biotin Phosphorous Used in DNA, RNA, and ATP, Found in membranes Trace elements Oxygen Organic growth factor
Macronutrients (needed in relatively large amounts) are often listed as CHONPS. What does each of these letters indicate, and why are they needed by the cell?
Carbon: synthesis of molecules that make up a living cell. Hydrogen: source of electrons and component of organic molecules. Oxygen: component of organic molecules; electrons acceptor in aerobes. Nitrogen: component of amino acids. Phosphorus: in phospholipids and nucleic acids. Sulfur: in some amino acids.
Define and explain the importance of peroxidase.
Catalyzes the breakdown of H2O2;NADH + H+ + H2O2 --perioxidase--> NAD+ + 2H2O2
Define and explain the importance of superoxide dismutase.
Converts superoxide to O2 and H2O2;2O2- + 2H+ --superoxide dismutase--> O2 + H2O2The enzymes are important in protecting the cell from strong oxidizing agents, perioxide and superoxide, that form during respiration.
Describe transcription
Copying part of the nucleotide sequence of DNA into a complementary sequence in RNA
Which of the following is NOT a sign or symptom of the common cold? A) Fever B) Runny nose C) Coughing D) Diarrhea
D) Diarrhea As a viral infection of the upper respiratory system, a common cold often results in fever, a runny nose, and a cough.
Compare and contrast the multiplication cycle of DNA- and RNA-containing animal viruses.
DNA •viruses replicate their DNA in the nucleus of the host using viral enzymes •Synthesize capsid in the cytoplasm using host cell enzymes RNA •Virus multiplies in the host cell's cytoplasm using-dependent RNA polymerase -ssRNA; + (sense) strand §Viral RNA serves as mRNA for protein synthesis -ssRNA; - (antisense) strand §Viral RNA is transcribed to a + strand to serve as mRNA for protein synthesis -dsRNA—double-stranded RNA RNA Viruses That Use DNA •Single-stranded RNA, produce DNA -Use reverse transcriptase to produce DNA from the viral genome §Viral DNA integrates into the host chromosome as a provirus -Retroviridae §Lentivirus (HIV) §Oncoviruses
Think about the process of DNA replication, the enzymes involved in the process, and the results of the process. Select the statements that accurately describe DNA replication.
DNA helicase separates the DNA strands, creating a replication fork. DNA replication is semiconservative. DNA replication occurs prior to mitosis and prior to binary fission. DNA replication can copy plasmids, which can be transferred among bacterial cells of the same generation. Topoisomerase and DNA gyrase remove supercoiling ahead of the replication fork. The major replication enzyme is DNA polymerase. DNA replication provides an exact copy of DNA for daughter cells (next generation).
What is the role of DNA helicase in DNA replication?
DNA helicase uses the energy from ATP to break the hydrogen bonds between two DNA strands, thereby "unzipping" the molecule.
Transduction in bacteria
DNA is transferred from a donor cell to a recipient via a bacteriophage
Which enzyme(s) can synthesize new strands of DNA?
DNA polymerase
The process of copying DNA prior to cell replication is known as _____________.
DNA replication
Which of the following is true regarding cultivation and isolation of animal viruses?
Diploid cell culture lines, developed from human embryos, are widely used for culturing viruses that require a human host.
Which of the following is true concerning a lysogenic viral replication cycle?
During lysogeny, the viral genome integrates into the host DNA, becoming a physical part of the chromosome.
Describe the chemical and physical structure of both an enveloped and a nonenveloped virus.
ENVELOPED: In some viruses, the capsid is covered by an envelope, which chemically, usually consists of some combination of lipids, proteins, and carbs. In most cases, the envelop contains proteins determined by the viral nucleic acid and materials derived from normal host cell componants. Structurally, the enveloped virus consists of the nucleic acid>>Capsomeres>> Envelop>>Spikes(on some enveloped viruses). NONENVELOPED: Are viruses whose capsids are not covered by an envelope. The capsid protect the viruses from nuclease enzymes in biological fluids and promotes the viruses attachment to susceptible host cells.
Mature viruses are made during which stage?
assembly
Compare protein synthesis in prokaryotes and eukaryotes.
In prokaryotes, protein synthesis, the process of making protein, occurs in the cytoplasm and is made of two steps: transcription and translation. ... Translation occurs at the same time that transcription is happening in prokaryotes. This is coupled transcription. In eukaryotes, transcription occurs in the nucleus, and translation occurs in the cytoplasm.
Where would one find an uncharged tRNA molecule in a ribosome?
In the P and E sites
Identify ways in which aerobes avoid damage by toxic forms of oxygen.
In the phagolysosome of the phagocytic cell, ingested pathogens are KILLED by exposure to these toxic forms of oxygen. -Singlet oxygen: O2 boosted to a higher-energy state. Toxic form of oxygen, neutralized by pigments called **CAROTENOIDS.-Superoxide free radicals: Toxic form of oxygen that is detoxified by ** SUPEROXIDE DISMUTASE.-Peroxide anion: Toxic form of oxygen which is detoxified by catalase or peroxidase **CATALASE or PEROXIDASE.-Hydroxyl radical: Most reactive of the toxic forms of oxygen.
Describe protein synthesis, including transcription, RNA processing, and translation.
In the process of transcription, genetic info in DNA is copied, or transcribed, into a complementary base sequence of RNA. The cell then uses the info encoded in this RNA to synthesize specific proteins thru the process of translation.
Bacterial Division
Increase in number of cells, not cell size Binary fission Budding Conidiospores (actinomycetes) Fragmentation of filaments
How would one increase the concentration of a particular polypeptide in a cell?
Increase the level of transcription
Glycolysis
Input: 1 glucose, 2 ATP, 2 NAD+ 4 ADP Output: 2 Pyruvates 2 NADH2 4 ATP Location: The cytoplasm (both Prokaryotes and Eukaryotes)
Krebs Cycle
Input: 2 Acetyl CoA 6 NAD+ 2 ADP 2 FAD Output: 4 CO2 6 NADH 2 FADH2 2 ATP Localization: Matrix of Mitochondria (Eukaryotes) Folding of the plasma membrane (Prokaryotes)
Electron Transport Chain
Input: 2 FADH2 10 NADH 02 (oxygen) Output: 34 ATP H2O Localization: Plasma membrane (Prokaryotes) Inner membrane of mitochondria (Eukaryotes)
Conversion of Pyruvate to Acetyl-CoA
Input: 2 Pyruvates 2 NAD+ Output: 2 Acetyl CoA 2 NADH2 2 CO2 Localization: Matrix of Mitochondria (Eukaryotes) Folding of the plasma membrane (Prokaryotes)
How does the DNA polymerase know which nucleotide triphosphate to add to the growing strand?
It hydrogen-bonds the nucleotide to the parental strand, pairing adenines to thymines and guanines to cytosines.
what is unique about the DNA transferred between two cells during conjugation?
It is transferred as a single strand.
Why is primase essential for DNA replication?
It provides a 3' end of the newly synthesized strand, allowing DNA polymerase to begin copying DNA.
Compare the phases of microbial growth, and describe their relation to generation time.
LAG PHASE- period of little or no cell division, can last for 1 hour or several days; however, cells are not dormant. undergoing intense metabolic activity involving synthesis of enzymes and various moleculesLOG PHASE- cells begin to divide and enter a period of growth. reproduction is active during this period and generation time reaches a constant minimum. since constant, it is a straight line. cells are most active metabolically and is preferred for industrial purposes where a produce needs to be producedSTATIONARY PHASE- period of equilibrium. growth rate slows, microbial deaths balances the number of new cells and the population stabilizesDEATH PHASE- the number of deaths eventually exceeds to number of new cells formed. phase continues until population is diminished to a tiny fraction of cells or until it dies out completely.
Which of the following are the main causative agents of the common cold?
Rhinoviruses and coronaviruses Common colds are viral infections; they are caused most commonly by rhinoviruses, coronaviruses, and some previously unclassified viruses.
Which of the following statements are true? S strains are capable of causing disease in mice. R strains are unable to cause disease in mice. R strains do not produce a capsule. All of the above statements are true. None of the above statements are true.
S strains are capable of causing disease in mice. R strains are unable to cause disease in mice. R strains do not produce a capsule. All of the above statements are true. None of the above statements are true.
Which of the following characteristics is a hallmark of bacterial growth?
Since the number of bacterial cells double after each round of replication, the number of cells rapidly increases.
Okazaki fragments
Small fragments of DNA produced on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand.
Which statement concerning viral structure is true?
Spikes are found on some viruses. They are very consistent in structure and can be used for identification.
How is pathogenic Staphylococcus aureus distinguished from other species of Staphylococcus?
Staphylococcus aureus is able to ferment mannitol, while other members of the genus are not.
Starting with a single parent cell, how many cells would there be after four rounds of binary fission?
Starting with a single parent cell, how many cells would there be after four rounds of binary fission?
In this activity, you will correctly identify the three methods of DNA transfer in bacteria. Match the image with the appropriate term identifying a mechanism of gene transfer and recombination.
TRANSFORMATION: vertical/recipient cell & DNA fragments going into a cell CONJUGATION: horizontal/3 paired cells-F factor & mating bridge TRANSDUCTION: vertical/phages
Which of the following statements concerning viruses is true?
The "host range" for a virus is determined by the presence or absence of particular components on the surface of a host cell that are required for the virus to attach.
What reason most likely explains the recovery of S strain from a mouse injected with heat-killed S strain mixed with living R strain?
The R strain picked up the S-strain DNA, enabling it to produce capsules.
quorum sensing
The ability of bacteria to sense the presence of other bacteria via secreted chemical signals.
What do all of these bacteria have in common? Bacteria in the rumen of cattle and sheep Bacteria in a sewage treatment plant Bacteria growing in the middle ear in chronic otitis media Bacteria growing on the teeth in dental plaque
The bacteria are most likely growing in biofilms.
When bacteria are inoculated into a new sterile nutrient broth, their numbers don't begin to increase immediately. Instead, there is a lag phase that may last for an hour or even several days. Why don't bacterial numbers increase immediately?
The bacteria must adjust to the nutrient content in the new medium, synthesizing necessary amino acids, growth factors, and enzymes
After a period of rapid growth (log phase), bacterial growth rates will slow and enter the stationary phase. The number of viable cells no longer increases, but instead stays constant. In this activity, you will indicate the statements that correctly describe what is happening during stationary phase. The cells are dead; therefore, the number is staying constant. Harmful waste products may be accumulating. The number of cells that are dying is balanced by the number of new cells that are being formed. The cells are likely running out of nutrients. Cells are not increasing in number because they have not yet adjusted to the nutrient availability in the new media.
The cells are likely running out of nutrients.- Harmful waste products may be accumulating.- The number of cells that are dying is balanced by the number of new cells that are being formed.
Why do cells that are placed in fresh media not immediately enter logarithmic phase of growth?
The cells need to switch their metabolic state from a dormant one to an actively growing one.
Which statement is INCORRECT concerning animal viruses?
The genome of animal viruses is always single-stranded.
By deep-freezing, bacteria can be stored without harm for extended periods. Why do refrigeration and freezing preserve foods?
The growth rate of bacteria slows down with decreasing temperatures. Mesophilic bacteria will grow slowly at refrigeration temperatures and will remain dormant in a freezer. Bacteria will not spoil food quickly in a refrigerator
Why are hyperthermophiles that grow at temperatures above 100°C seemingly limited to oceanic depths?
The immense pressure in the ocean depths prevents water from boiling even at temperatures well above 100°C.
Which of the following statements concerning DNA replication is true?
The leading strand of DNA replication requires only one RNA primer.
Which of the following statements regarding biofilms is true?
The microbes in biofilms can work cooperatively to carry out complex tasks.
Why are the beta-pleated multimers of PrP potentially pathogenic?
The multimers are more stable and resistant to protease.
What is meant by semiconservative replication?
The new copies of DNA contain one original strand of DNA and one new strand of DNA.
What might happen if the cell does not have RNAse?
The newly made chromosome would consist of DNA and RNA molecules.
What must occur for an organism to pass its genetic information on to its offspring?
The parent must copy its own DNA and provide a copy to its offspring.
Describe the lysogenic cycle of bacteriophage lambda.
The phage genome also enters the cell through attachment and penetration. A prime example of a phage with this type of life cycle is the lambda phage. During the lysogenic cycle, instead of killing the host, the phage genome integrates into the bacterial chromosome and becomes part of the host.
Why is E. coli considered the model of bacterial conjugation?
The process of conjugation is best characterized in E. coli.
Which of the following is a viral benefit of lysogeny?
The prophage gets replicated every time the cell replicates.
why does treatment of a wound with hydrogen peroxide results in bubbling?
The reason why it foams is because blood and cells contain an enzyme called catalase
host range
The spectrum of host cells a virus can infect • Most viruses infect only specific types of cells in one host • Determined by specific host attachment sites and cellular factors
Which of the following represent a true statement about the resulting new daughter cells?
They are genetically identical to the parent
Other than controlling acidity, what is an advantage of using phosphate salts as buffers in growth media?
They are nontoxic they provide phosphorus, an essential nutrient
Which of the following statements regarding Okazaki fragments are true?
They are typically 1000 nucleotides in length.
How do prions replicate?
They cause normal proteins to misfold into infectious proteins.
DNA/Chromosomes
They contain genes along their length; these genes are hereditary information and serve as instructions on how to build proteins.•Bacteria usually have a single circular chromosome made of DNA and associated proteins
What is the function of stabilizing proteins?
They hold the separated strands apart and prevent their degredation.
How are prions different from other infectious agents?
They lack nucleic acid.
What is the function of the connector proteins?
They link the leading strand DNA polymerase and the lagging strand DNA polymerase together.
What are the two steps A. baumannii uses to produce proteins from DNA?
Transcription and translation
Sort the following items according to whether they are associated with transcription, translation, both, or neither. Drag each item into the appropriate bin.
Transcription: RNA polymerase, DNA, ribonucleotides, promoter Translation: codon and anticodon pairing, ribosome, amino acids Both transcription and translation: mRNA and tRNA Neither transcription and translation: DNA polymerase, deoxyribonucleotides
A strain of Neisseria gonorrhoeae that was formerly sensitive to penicillin has recently acquired the ability to produce penicillinase, an enzyme that inactivates penicillin. Evidence indicates that this is not a new mutation but rather a gene received from another bacterium. The gene is now spreading rapidly among the population, causing the recipient bacteria to be resistant to penicillin. Place the following steps in the order in which they most likely occurred to result in the production of penicillinase. Drag items into the boxes provided to indicate the order in which they occur.
Transformation introduced the penicillinase gene to this strain of Neisseria gonorrhoeae Recombination occurred, placing the penicillinase gene in the Neisseria gonorrhoeae genome. The penicillinase gene was replicated along with all of the other DNA prior to cell division, resulting in the vertical transmission of the gene to daughter cells. The penicillinase gene was transcribed into mRNA The penicillinase mRNA was translated into the protein penicillinase
This activity requires that you sort statements according to whether they are associated with transformation, conjugation, or transduction. Drag the statement to the gene transfer mechanism with which it is associated. A statement may be associated with more than one mechanism.
Transformation: Extracellular DNAases would block this transfer mechanism. This mechanism was first explored by Griffith as he studied smooth and rough strains of Streptococcus pneumoniae. Conjugation: This mechanism is initiated by cells with F plasmids. This mechanism requires cell-to-cell contact. A chemical that blocked the formation of a pilus would block this genetic transfer mechanism. Transduction: A virus that infects bacteria is a key component in this transfer mechanism. All mechanisms: This mechanism of genetic transfer always involves a one-way transfer from a donor cell to a recipient cell. This mechanism may result in the transfer of genes that encode antibiotic resistance.
Lytic bacteriophages destroy their hosts.
True
Differentiate a virus from a bacterium
Viruses are intracellular parasites that can pass through bacteriological filters and are sensitive to interferons. They have no plasma membrane, ribosomes, do not perform binary fission, only contain one nucleic acid, and are not sensitive to antibiotics. All bacteria have plasma membranes, use binary fission, possess both nucleic acids, have ribosomes, and are sensitive to antibiotics but not to interferons.
Which of the following statements best describes why antibiotics are ineffective treatments for the common cold? Viruses contain enzymes that deactivate antibiotics before they can reach their targets. Viruses do not possess targets for antibiotics. Viruses are constantly mutating and changing their antibiotic targets. Viruses contain drug pumps that pump antibiotics out of the virus before the antibiotic can reach its target.
Viruses do not possess targets for antibiotics.
What factors that are important when formulating culture media?
Water availability O2 levels pH
How is translation terminated?
When a protein called a release factor enters and binds to the A site
The normal function of the PrP protein in mammals is believed to be:
assisting in normal synaptic development and function
replication fork
a Y-shaped point that results when the two strands of a DNA double helix separate so that the DNA molecule can be replicated
Define oncogene
a gene that in certain circumstances can transform a cell into a tumor cell.
Mutation
a permanent change in the base sequence of DNA. •Mutations may be neutral, beneficial, or harmful
which of the following is a characteristic of an F+ cell?
ability to synthesize sex pili, presence of fertility factor, ability to mate with an F- cell
An organism that has peroxidase and superoxide dismutase but lacks catalase is most likely an
aerotolerant anaerobe
Mutagens
agents that cause mutations
The replication fork moves ___________.
ahead of the newly synthesized DNA.
Which of the following bacterial cell structures increases in size during binary fission? cell wall bacterial chromosome cell membrane cytoplasm both the cell wall and cell membrane all of the above
all of the above
silent mutation
alters a base but does not change the amino acid and thus has no effect
if bacterial cells were given a sulfur source containing radioactive sulfur (35S) in their culture media, in what molecules would the 35S be found in the cells?
amino acids, proteins, RNA and DNA
characteristics of biofilm
antibiotic resistance, hydrogel, quorum sensing
Codons are
are groups of three mRNA nucleotides that code for a particular amino acid
dsDNA viral capsomeres __________________.
are synthesized in the cytoplasm. are assembled in the nucleus.
Define bacterial growth, including binary fission.
bacterial growth refers to an increase in bacterial numbers, not an increase in the size of individual cells. they usually reproduce by binary fission. a few species reproduce by budding.
oncogenic viruses
become integrated into the host cell's DNA and induce tumors
Most bacteria divide by which method?
binary fission
When a bacterial cell reproduces by splitting into two daughter cells, the process is called __________.
binary fission
Release factors _________________________.
bind to the A site AND are coded by stop codons.
Microbes adhere to surfaces and accumulate as ______________ on solid surfaces in contact with water.
biofilms
Most bacteria live in
biofilms
In which stage is the host chromosome broken into small fragments?
biosynthesis
The stage in which viral proteins are produced is the ___________________.
biosynthesis stage.
Some bacteria reproduce by
budding, aerial spore formation, or fragmentation
Which of the following phases of the bacterial growth curve is matched with the correct definition? a. lag phase--the phase in which the death of organisms exceeds the creation of new cells and the curve declines b. stationary phase--the phase in which cells are not dividing very rapidly as they acclimatize to a new environment c. log phase--the phase in which organisms are actively dividing and the generation time is constant d. death phase--the phase in which the curve is flat; microbial deaths balance the number of new cells
c. log phase--the phase in which organisms are actively dividing and the generation time is constant
Base substitution (point mutation)
change in one base in DNA
All organisms require a carbon source;
chemoheterotrophs use an organic molecule, and autotrophs typically use carbon dioxide.
Cells that are naturally able to take up DNA from their environment are said to be ___________________.
competent.
why does conjugation between an Hfr strain and an F- strain not result in two Hfr strains?
conjugation is typically disrupted before the fertility factor can be transferred
During which phase of bacterial growth will the number of dying cells exceed the number of new cells being made? ag phase log phase stationary phase death phase
death phase
what is the purpose of culture media?
designed to support the growth of microorganisms
Which of the following is NOT a step in bacterial cell division? replication of the genetic material cell elongation disappearance of nuclear envelope splitting apart of two new daughter cells
disappearance of nuclear envelope
During log phase, bacteria are:
dividing at the fastest possible rate
What serves as the template for DNA replication?
each of the original DNA strands
Name a use for phosphorus needed in large amounts for microbial growth.
essential for the synthesis of nucleic acids and phospholipids of cell membranes, found in bonds of ATP
Phenotype
expression of the genes
Flow of genetic information
expression, recombination, replication DNA is the blueprint for a cells proteins, including enzymes. DNA is obtained from either another cell in the same generation or from a parent cell during cell division. DNA can be expressed within a cell or transferred to another cell through recombination or replication
An organism that grows both in the presence and the absence of oxygen and uses oxygen when it is available is called a(n) __________.
facultative anaerobe
Bacteria that can grow in the presence or absence of oxygen (O2) are called __________.
facultative anaerobes
vertical gene transfer
flow of genetic information from one generation to the next
What type of mutation can change all subsequent amino acids following it?
frameshift mutation
A base insertion or deletion in the translated region of the gene may lead to
frameshift mutation.
how is generalized transduction different from specialized transduction?
generalized transduction is initiated during lytic cycle of a virulent bacteriophage; specialized transduction is initiated during the lysogenic cycle of a temperate bacteriophage
Transformation in Bacteria
genes transferred from one bacterium to another as "naked" DNA
genotype
genetic makeup of an organism
Anticodon
group of three bases on a tRNA molecule that are complementary to an mRNA codon
Acidophiles
grow in acidic environments
facultative anaerobes
grow via fermentation or anaerobic respiration when oxygen is not available
Transformed cells
have increased growth, loss of contact inhibition, tumor-specific transplant antigens, and T antigens happens when cells take in foreign DNA and express the genes encoded on that DNA. The expression of the genes gives the cell new characteristics, literally transforming the cell.
Facultative halophiles tolerate
high osmotic pressure
Extreme or obligate halophiles require
high osmotic pressure (high salt)
In general, higher levels of transcription lead to ______________________.
higher amounts of protein.
Types of frameshift mutations
insertion - a mutation in which one or more pairs of nucleotides are inserted into a gene deletion - a mutation in which one or more pairs of nucleotides are removed from a gene
The following steps occur during binary fission. What is the third step?
inward growth of membrane After DNA replication and cell elongation, the membrane will grow inward between the two newly formed cells.
genetic code
is a set of rules that determines how a nucleotide sequence is converted to an amino acid sequence of a protein
The replication fork __________________.
is the point where DNA helicase is "unzipping" the double-stranded DNA molecule.
what benefit does the F- strain receive from mating with an Hfr strain?
it acquires new, potentially beneficial genes from the Hfr strain
How would one determine whether a microbe is a strict anaerobe?
it will only grow at the BOTTOM where there is NO O2
During which phase of bacterial growth would you see cell dividing most rapidly? lag phase log phase stationary phase death phase
log phase
Bacterial division occurs according to
logarithmic progression
Which of the following is NOT a step in binary fission? Replication of chromosomal DNA Cross-wall formation Cell elongation Invagination of the plasma membrane Lysis of the existing cell wall
lysis of the existing cell wall
Which of the following is a component of temperate bacteriophage life cycle?
lysis of the host prophage lysogeny
Which of the following is not a part of the initiation complex?
mRNA
Which of the following is the copy of a DNA sequence used to make protein?
mRNA
Which of the following is a product of transcription?
mRNA rRNA tRNA
Bacteria growing in and on the human body, including normal microbiota as well as pathogens, are classified as __________.
mesophilic and heterotrophic
Campylobacter bacteria are grown with a CampyPak that produces 5% carbon dioxide and 15% oxygen. This bacterium is __________. A. capnophile B. microaerophile C. aerotolerant anaerobe D. anaerobe
microaerophile
A chemical that can increase the rate of mutations is called a _______________________.
mutagen.
Which of the following viral attachment mechanisms involves host receptor proteins?
naked virus attachment enveloped virus membrane fusion enveloped virus-induced phagocytosis
The ability of microbes to utilize N2 as a nitrogen source is called _____.
nitrogen fixation
A base substitution that changes a codon coding for an amino acid to a stop codon is called a
nonsense mutation.
A mutation that results in the presence of a stop codon in the middle of the genetic code is a _____________.
nonsense mutation.
Bacterial growth refers to an increase in the __________ of bacterial cells.
number
An unknown organism grows at the top of a tube of thioglycolate broth. This organism is best described as a(n) __________ for its oxygen requirements.
obligate aerobe
Bacteria that CANNOT grow in the presence of oxygen (O2) are called __________.
obligate anaerobes
Instead of oxygen, __________ may utilize nitrate or sulfate as their final electron acceptors.
obligate anaerobes
spontaneous mutations
occur in the absence of a mutagen
pH: Molds and yeasts grow between
pH 5-6
pH most bacteria grow between
pH 6.5-7.5
Which phase involves the injection of bacteriophage DNA?
penetration
Hypertonic environments (higher in solutes than inside the cell) cause
plasmolysis due to high osmotic pressure
This activity asks you to consider various methods of counting or estimating the size of bacterial populations and to select the method that will provide the most accurate data for plotting a bacterial growth curve. Which of the following methods would be most appropriate for gathering data to plot a bacterial growth curve throughout the four phases? direct microscopic count Any of these methods will provide reliable data for plotting a growth curve. plate count indirect estimate based on turbidity electronic cell counter
plate count
Outline the methods of direct and indirect selection of mutants.
positive (direct) selection: detects mutant cells because they grow or appear different- involves the detection of mutant cells by rejection of the unmated parent cells. negative (indirect) selection: detects mutant cells because they do not grow
DNA polymerase
principle enzyme involved in DNA replication
gene expression
process by which a gene produces its product and the product carries out its function (phenotype)
Oxygen is so pervasive in the environment that it would be very difficult for a microbe to always avoid physical contact with it. What, therefore, is the most obvious way for a microbe to avoid damage?
produce enzymes to neutralize them against toxicity
A virus will co-opt the host cell machinery to ________________________.
produce viral proteins replicate the genetic material
An organism displays some growth at 4°C and at 25°C. However, it grows best at 20°C. This organism would be classified as a __________.
psychrotroph
Bacteria that spoil food in the refrigerator are most likely __________.
psychrotrophs
A cell that has incorporated new DNA as part of its own is termed a __________.
recombinant.
short tandem repeats (STRs)
repeating sequences of noncoding DNA
Microaerophiles
require oxygen concentration lower than air
Gene
segments of DNA that encode functional products, usually proteins
Which mutation is the least likely to be harmful to a cell?
silent mutation
During which phase of the cell cycle are bacteria dividing equal to bacteria dying?
stationary phase
RNA that has hydrogen bonded to itself forms a
stem loop
Name a use for each carbon needed in large amounts for microbial growth.
structural organic molecule, energy source, organic compounds that makeup living cells chemoheterotrophs use organic carbon source, autotrophs use CO2.
Chromosomes
structures containing DNA that physically carry hereditary information; the chromosomes contain genes
Which of the following is involved in bringing amino acids to the ribosomes?
tRNA
Physical requirements for growth
temperature, pH, osmotic pressure
RNA polymerase is guided by the
template strand of DNA
when a transducing phage interacts with a new host cell
the DNA from the previous shot can recombine with the new host chromosome
What is quorum sensing?
the ability of bacteria in a biofilm to communicate with each other and coordinate their activities
Endoplasmic Reticulum (Eukaryotic Cells)
•Folded transport network •Rough ER: studded with ribosomes; sites of protein synthesis •Smooth ER: no ribosomes; synthesizes cell membranes, fats, and hormones
Identify a way in which pathogens find it advantageous to form biofilms.
the bacteria are able to share nutrients and are sheltered from harmful factors in the environment. the close proximity may also facilitate the transfer of genetic information
During Log Phase
the bacteria multiply at the fastest rate possible under the conditions provided
bacterial conjugation
the direct transfer of genetic material (DNA) from one bacterial cell to another •Donor cells carry the plasmid (F factor) and are called F+ cells •Hfr cells contain the F factor on the chromosome
The time required for a cell to divide or a population to double is known as
the generation time.
The maximum growth temperature is
the highest temperature at which growth is possible.
The minimum growth temperature is
the lowest temperature at which the species will grow
During the death phase,
the number of deaths exceeds the number of new cells formed
Describe how DNA serves as genetic information.
the structure of DNA helps explain two primary features of biological info storage. -first, the linear sequence of bases provides the actual info -genetic info is encoded by the sequence of bases along the strand of DNA, in much the same way as our written language uses linear sequence of letters to form words and sequences
During the stationary phase
there is an equilibrium between cell division and death
During the lag phase
there is little or no change in the number of cells, but metabolic activity is high, cells are engaged in intense enzymatic activity
You inoculate two tubes of liquid culture medium with 100 bacterial cells and incubate one tube at 37°C and the other at 55°C. After 48 hours, there are 20,000 bacteria per milliliter in the 37°C tube and 1,568,000 bacteria per milliliter in the 55°C tube. You conclude that this species is a ________
thermophile
what is unique about transduction compared to normal bacteriophage infection?
tranduction transfers DNA from chromosome of one cell to another
In a hypertonic solution, most microbes undergo plasmolysis; halophiles can tolerate high salt concentrations.
undergo plasmolysis; halophiles can tolerate high salt concentrations.
Name a use sulfur needed in large amounts for microbial growth.
used to synthesize sulfur-containing amino acids and vitamins
An amino acid is considered charged ____________.
when it is bound to its correct tRNA.
2 types of bacterial transduction
•Generalized transduction: Random bacterial DNA is packaged inside a phage and transferred to a recipient cell •Specialized transduction: Specific bacterial genes are packaged inside a phage and transferred to a recipient cell
General Morphology
•Helical viruses—hollow, cylindrical capsid •Polyhedral viruses—many-sided •Enveloped viruses •Complex viruses—complicated structures
Substrate-Level Phosphorylation
• ATP is generated when high-energy PO4- is added to ADP
DNA oncogenic viruses
• Adenoviridae • Herpesviridae Epstein-Barr virus • Poxviridae • Papovaviridae Human papillomavirus • Hepadnaviridae Hepatitis B virus
Ribosomes (Eukaryotes)
•80S -Consists of the large 60S subunit and the small 40S subunit -Membrane-bound: attached to endoplasmic reticulum In chloroplasts and mitochondria
Atypical Cell Wall
•Acid-fast cell walls -Like gram-positive cell walls -Waxy lipid (mycolic acid) bound to peptidoglycan -Mycobacterium -Nocardia -Stain with carbolfuchsin
Axial Filaments of Prokaryotic Cells
•Also called endoflagella •Found in spirochetes •Anchored at one end of a cell •Rotation causes cell to move like a corkscrew
Describe the lytic cycle of T-even bacteriophages.
•Attachment: phage attaches by the tail fibers to the host cell •Penetration: phage lysozyme opens the cell wall; tail sheath contracts to force the tail core and DNA into the cell •Biosynthesis: production of phage DNA and proteins •Maturation: assembly of phage particles •Release: phage lysozyme breaks the cell wall
Nucleoid (Prokaryotes)
•Bacterial chromosome: circular thread of DNA that contains the cell's genetic information •Plasmids: extrachromosomal genetic elements; carry non-crucial genes (e.g., antibiotic resistance, production of toxins)
Catabolic and Anabolic Reactions
•Catabolism: breaks down complex molecules; provides energy and building blocks for anabolism; exergonic •Anabolism: uses energy and building blocks to build complex molecules; endergonic exergonic- releases more energy than absorbed endergonic- absorbs more energy than releases
Enzymes and Chemical Reactions
•Catalysts speed up chemical reactions without being altered •Enzymes are biological catalysts •Enzymes act on a specific substrate and lower the activation energy
Cell Wall and Glycocalyx (Eukaryotes)
•Cell wall -Found in plants, algae, and fungi -Made of carbohydrates (cellulose—plants, chitin—fungi, glucan and mannan—yeasts) •Glycocalyx -Carbohydrates bonded to proteins and lipids in the plasma membrane Found in animal cells
Aerobic Respiration
•Chemiosmosis -Electrons (from NADH) pass down the electron transport chain while protons are pumped across the membrane §Establishes proton gradient (proton motive force) -Protons in higher concentration on one side of the membrane diffuse through ATP synthase §Releases energy to synthesize ATP
Mitochondria (Eukaryotes)
•Double membrane •Contain inner folds (cristae) and fluid (matrix) •Involved in cellular respiration (ATP production)
Carbohydrate Catabolism
•Each NADH can be oxidized in the electron transport chain to produce 3 molecules of ATP •Each FADH2 can produce 2 molecules of ATP
Aerobic Respiration
•Electron transport chain (system) -Occurs in the plasma membrane of prokaryotes; inner mitochondrial membrane of eukaryotes -Series of carrier molecules (flavoproteins, cytochromes, and ubiquinones) are oxidized and reduced as electrons are passed down the chain -Energy released is used to produce ATP by chemiosmosis
Oxidative Phosphorylation
•Electrons are transferred from one electron carrier to another along an electron transport chain (system) on a membrane that releases energy to generate ATP -Chemiosmosis is the term for the process wherein ATP is generated from ADP using the energy derived from the electron transport chain
DNA replication
•Energy Needs -Energy for replication is supplied by nucleotides -Hydrolysis of two phosphate groups on ATP provides energy. Most bacterial DNA replication is bidirectional Each offspring cell receives one copy of the DNA molecule Replication is highly accurate due to the proofreading capability of DNA polymerase
Enzyme Specificity and Efficiency
•Enzymes have specificity for particular substrates •Turnover number is the number of substrate molecules an enzyme converts to a product per second -Generally 1 to 10,000 -Can be as high as 500,000
Glycocalyx of Prokaryotic Cells
•External to the cell wall •Viscous and gelatinous •Made of polysaccharide and/or polypeptide •Two types -Capsule: neatly organized and firmly attached -Slime layer: unorganized and loose •Contribute to virulence (the degree to which a pathogen can cause disease) -Capsules prevent phagocytosis -Extracellular polymeric substance helps form biofilms
Flagella in Prokaryotic Cells
•Filamentous appendages external of the cell •Propel bacteria •Made of protein flagellin •Three parts: -Filament: outermost region -Hook: attaches to the filament -Basal body: consists of rod and pairs of rings; anchors flagellum to the cell wall and membrane •Flagella allow bacteria to move toward or away from stimuli (taxis)- chemotaxis (chemical stimuli) or phototaxis (light stimuli) •Flagella rotate to "run" or "tumble" Atrichous- no flagella Peritrichous- flagella all around Polar- flagella on one side or both Monotrichous- one flagellum on one side Lophotrichous- tuft of flagella from one pole amphitrichous- flagella at both ends of poles
Fimbriae and Pili of Prokaryotic Cells
•Fimbriae -Hairlike appendages that allow for attachment •Pili -Involved in motility (gliding and twitching motility) -Conjugation pili involved in DNA transfer from one cell to another Gliding- smooth gliding motion Twitching- pilus extends by the addition of subunits of pilin, makes contact with a surface or another cell, and then retracts (powerstroke) as the pilin subunits are disassembled
Describe how animal viruses are cultured.
•In living animals •In embryonated eggs -Virus injected into the egg -Viral growth is signaled by changes or death of the embryo•In cell cultures -Tissues are treated with enzymes to separate cells -Virally infected cells are detected via their deterioration, known as the cytopathic effect (CPE) -Continuous cell lines are used
trace elements
•Inorganic elements required in small amounts •Usually as enzyme cofactors •Include iron, copper, molybdenum, and zinc
radiation mutagens
•Ionizing radiation (X-rays and gamma rays) causes the formation of ions that can oxidize nucleotides and break the deoxyribose-phosphate backbone •UV radiation causes thymine dimers
Aerobic Respiration
•Krebs cycle -Pyruvic acid (from glycolysis) is oxidized and decarboxylation (loss of ) occurs -The resulting two-carbon compound attaches to coenzyme A, forming acetyl CoA and NADH -Oxidation of acetyl CoA produces NADH, , and ATP, and liberates CO2 as waste
Catabolic and Anabolic Reactions
•Metabolic pathways are sequences of enzymatically catalyzed chemical reactions in a cell •Metabolic pathways are determined by enzymes •Enzymes are encoded by genes
Inclusions (Prokaryotes)
•Metachromatic granules (volutin)—phosphate reserves •Polysaccharide granules—energy reserves •Lipid inclusions—energy reserves •Sulfur granules—energy reserves •Carboxysomes—RuBis enzyme for fixation during photosynthesis •Gas vacuoles—protein-covered cylinders that maintain buoyancy •Magnetosomes—iron oxide inclusions; destroy hydrogen peroxide
Biofilms
•Microbial communities •Form slime or hydrogels that adhere to surfaces - Bacteria communicate cell-to-cell via quorum sensing - Bacteria secrete an inducer (signaling chemical) to attract other bacterial cells •Share nutrients •Shelter bacteria from harmful environmental factors •Found in digestive system and sewage treatment systems; can clog pipes •1000x resistant to microbicides •Involved in 70% of infections - Catheters, heart valves, contact lenses, dental caries
Naming Enzymes
•Names of enzymes usually end in ase; grouped based on the reaction they catalyze •Oxidoreductase: oxidation-reduction reactions •Transferase: transfer functional groups •Hydrolase: hydrolysis •Lyase: removal of atoms without hydrolysis •Isomerase: rearrangement of atoms •Ligase: joining of molecules; uses ATP
Nucleus (Eukaryotic cells)
•Nucleus -Double membrane structure (nuclear envelope) that contains the cell's DNA -DNA is complexed with histone proteins to form chromatin -During mitosis and meiosis, chromatin condenses into chromosomes
Cellular Respiration
•Oxidation of molecules liberates electrons to operate an electron transport chain •Final electron acceptor comes from outside the cell and is inorganic -Aerobic respiration uses oxygen as the final electron acceptor -Anaerobic respiration uses a molecule other than oxygen as the final electron acceptor •ATP is generated by oxidative phosphorylation
Oxidation-Reduction Reactions
•Oxidation: removal of electrons •Reduction: gain of electrons •Redox reaction: an oxidation reaction paired with a reduction reaction
The Size, Shape, and Arrangement of Bacterial Cells
•Pairs: diplococci, diplobacilli •Clusters: staphylococci •Chains: streptococci, streptobacilli •Groups of four: tetrads •Cubelike groups of eight: sarcinae
Cell Wall (prokaryotic cell)
•Prevents osmotic lysis and protects the cell membrane •Made of peptidoglycan (in bacteria) •Contributes to pathogenicity •Peptidoglycan -Polymer of a repeating disaccharide in rows: ▪N-acetylglucosamine (NAG) ▪N-acetylmuramic acid (NAM) •Rows are linked by polypeptides
Prions
•Proteinaceous infectious particles •Inherited and transmissible by ingestion, transplant, and surgical instruments In Humans -Spongiform encephalopathies "Mad cow disease" -Creutzfeldt-Jakob disease (CJD) -Gerstmann-Sträussler-Scheinker syndrome -Fatal familial insomnia -Kuru In animals -Sheep scrapie -Chronic wasting disease -Bovine spongiform encephalopathy -transmissible mink encephalopathy •PrPC: normal cellular prion protein, on the cell surface • PrPSc: scrapie protein; accumulates in brain cells, forming plaques
Endospores
•Resting cells; produced when nutrients are depleted •Resistant to desiccation, heat, chemicals, and radiation •Produced by Bacillus and Clostridium •Sporulation: endospore formation •Germination: endospore returns to vegetative state
Plasma Membrane (Eukaryotic Cells)
•Similar in structure to prokaryotic cell membranes -Phospholipid bilayer -Integral and peripheral proteins •Differences in structure -Sterols—complex lipids -Carbohydrates—for attachment and cell-to-cell recognition
Factors Influencing Enzyme Activity
•Temperature •pH •Substrate concentration •Inhibitors •High temperature and extreme pH denature proteins •If the concentration of substrate is high (saturation), the enzyme catalyzes at its maximum rate
Carbohydrate Catabolism
•The breakdown of carbohydrates to release energy typically occurs in three principle stages -Glycolysis -Krebs cycle -Electron transport chain (system)
Anaerobic Respiration
•The final electron acceptor in the electron transport chain is NOT oxygen (O2) -Yields less energy than aerobic respiration
Glycolysis
•The oxidation of glucose to pyruvic acid produces ATP and NADH •Preparatory stage -2 ATP are used -Glucose is split to form two molecules: one glyceraldehyde 3-phosphate (GP), and one dihydroxyacetone phosphate (DHAP) -DHAP is readily converted to GP •Energy-conserving stage -The two glyceraldehyde 3-phosphate molecules are oxidized to 2 pyruvic acid molecules -4 ATP are produced -2 NADH are produced •Overall net gain of two molecules of ATP for each molecule of glucose oxidized (process on different card)
Cytoplasm of Prokaryotes
•The substance inside the plasma membrane •Eighty percent water plus proteins, carbohydrates, lipids, and ions •Cytoskeleton functions- cell division, maintaining cell shape, growth, DNA movement, protein targeting, and alignment of organelles. The cytoplasm of prokaryotes is not capable of cytoplasmic streaming,
Gram Positive Cell Wall (Prokaryote)
•Thick peptidoglycan •Teichoic acids •Teichoic acids -Lipoteichoic acid links cell wall to plasma membrane -Wall teichoic acid links the peptidoglycan -Carry a negative charge -Regulate movement of cations •Polysaccharides and teichoic acids provide antigenic specificity
generation time
•Time required for a cell to divide -20 minutes to 24 hours •Binary fission doubles the number of cells each generation •Total number of cells = 2number of generations •Growth curves are represented logarithmically
Golgi Complex (Eukaryotic)
•Transport organelle •Modifies proteins from the ER •Transports modified proteins via secretory vesicles to the plasma membrane
Viral Structure
•Virion—complete, fully developed viral particle -Nucleic acid—DNA or RNA can be single- or double-stranded; linear or circular -Capsid—protein coat made of capsomeres (subunits) -Envelope—lipid, protein, and carbohydrate coating on some viruses -Spikes—projections from outer surface *sensitive to heat, detergents, and dessication *enveloped viruses are easier to kill