MICRO 106 Exam 2

What type of operon is the trp operon? Explain.

it is a corepressor it binds and activates the repressor to bind to the operator, stopping tryptophan synthesis

What is the function of the DNA polymerase and ligase?

joins Okazaki fragments

What is the mode of action of alcohols? Provide example.

kill bacteria, fungi, enveloped viruses; denatures proteins and dissolves lipids; more effective than soap in removing bacteria from hands; NOT effective for cleaning wounds; evaporates quickly and leaves no residue -ex: ethanol and isopropanol

Define bacteriocidal

killing

What is the mode of action of peroxygens? Provide example.

"toxic oxygen" -oxidizing agents -used for contaminated surfaces and food packaging ex: hydrogen peroxide, ozone, peracetic acid

How does filtration suppress microbial growth?

removes microbes

Describe photoreactivation

(light repair) -enzyme photolyase uses visible light to break covalent bonds between bases (breaks Thymine dimers)

Define and describe bacterial conjugation

-"bacteria sex" -plasmids transferred from one bacterium to another -uses sex pilus or mating bridge -donor cells carry "F factor" (F+) -recipient cell does not carry plasmid (F-)

Describe normal microbiota

-"normal flora", "indigenous microbiota" -organisms that colonize the body's surfaces without normally causing disease -distribution and composition are determined by: nutrients, physical and chemical factors, host defenses, mechanical factors

What happens in the lac operon model when: glucose present no lactose

-CAP cannot bind -RNA polymerase cannot bind -repressor can bind

What happens in the lac operon model when: glucose & lactose present

-CAP cannot bind -RNA polymerase cannot bind -repressor cannot bind, inducer comes in

Who did the experiment that led to the discovery of transformation? When? What bacteria did he use?

-Frederick Griffith -1928 -S. pneumoniae

What are trace elements? Some examples. Where are the naturally present?

-Inorganic elements that are required in small amounts -ex: cobalt, zinc, molybdenum, manganese -usually as enzyme cofactors -tap water

Define endotoxin. When is this released? What does this cause?

-Lipid A portion of lipopolysaccharides (LPS) of gram (-) bacteria -released during bacterial multiplication and when gram (-) lyse -septic shock

What are the 3 ways base substitution can be corrected? Briefly explain

-Silent mutation: a nucleotide change that generates a codon which still specifies the wild type (original) amino acid -Missense mutation- base substitution results in change in an amino aid -nonsense mutation: results in nonsense (stop) codon, makes truncated (shortened) protein

Define nosocomial infection. How common are these?

-acquired while receiving treatment in a health care facility -1 in 25 hospital patients -8th leading cause of death in USA

Describe a base substitution

-aka point mutation -most common type of mutation -one base pair is affected (one nucleotide on each strand) -results from mistakes during DNA synthesis -incorrect base is incorporated into DNA and not proofreading

What is the mode of action of halogens? Provide example.

-alter protein synthesis and membranes; used to treat water; skin disinfection and wound treatment -ex: iodine -common disinfectant of water and surfaces; oxidizing agents shut down cellular enzyme systems -ex: chlorine

What do nucleotide altering chemicals result in?

-base pair substitutions and missense mutations -converts amino group to keto group -changes adenine -adenine now binds to cytosine

What happens in the lac operon model when: no glucose or lactose present

-cAMP binds -RNA polymerase binds -repressor binds

What happens in the lac operon model when: No glucose Lactose present

-cAMP binds -RNA polymerase binds -repressor cannot bind, inducer comes in transcription takes place

How does radiation suppress microbial growth?

-can be ionizing where it ionizes water to create hydroxyl radicals and damages DNA by causing lethal mutations -can be nonionizing where is damages DNA by creating thymine dimers

What is the importance of a biofilm?

-cell-to-cell chemical communication (quorum sensing), allows bacteria to group into communities -share nutrients/sheltered from harmful factors -human health, 1000x more resistant to microbicides

Define and describe DNA-mediated transformation

-the transfer of naked DNA from one bacterium to another -discovered by Frederick Griffith

How does the time of exposure influence the effectiveness of a control method? What is the concept of equivalent treatments

-chemical antimicrobials often require extended exposure to affect more-resistant microbes -as temp increases, less time is needed to kill the same number of resistant microbes

What are the two groups of organisms based on source of energy?

-chemotrophs: redox reactions -phototrophs: light

Give examples of enzymes that promote pathogenicity

-coagulases: coagulate fibrinogen (forms clots) to wall off pathogen -kinases: digest fibrin clots designed to isolate infection -IgA proteases: destroy IgA antibodies

What is the mode of action of aldehydes ? Provide example.

-contain terminal -OH groups -inactive cross-linking with functional groups -used to perserve specimens and in medical equipment ex: formaldehyde, formalin

How does DNA serve as genetic information?

-control genetic expression -initiation of DNA replication -protection against viral infection -repair of DNA

What is the mode of action of heavy metals? Provide example.

-denatures proteins -can prevent blindness, creams are used to prevent secondary infections in burns ex: silver (Ag) -mercuric chloride is historical disinfectant, preserve vaccines ex: mercury (Hg) -copper sulfate is an algicide ex: copper (Cu) -zinc chloride is in mouthwash ex: zinc

How does the number of microbes influence the effectiveness of a control method?

-directly effects the time it takes to kill the population -gauged by decimal reduction time -washing reduces times required to reach disinfection or sterilization

What is the mode of action of phenol/phenolics? Provide example.

-disrupt lipids in plasma membranes; effectively in presence of organic matter; remain active for prolonged time; commonly used in health care setting, labs, and homes -ex: Lysol, Triclosan

What is the mode of action of biguanides? Provide example.

-disrupts plasma membranes ; used in surgical hand scrubbing -ex: chlorhexidine

What two forms did Griffith realize S. pneumoniae existed in? What were these like?

-encapsulated virulent form (smooth in appearance, S strain) -Nonencapsulated avirulent form (rough in appearance, R strain)

Explain induction/ lac operon

-example of inducible operon -"I" gene, codes for repressor protein ^^ whenever lactose is absent, the repressor protein binds to the lac operator -when lactose is present, the repressor binds to lactose instead of the operator -with the repressor bound to lactose, RNA polymerase is able to bind to the promoter, translocate through the operator, and transcribe the structural genes -lactose = inducedr

Purpose and procedure of the Ames test

-exposes mutant bacteria to mutagenic substances to measure the rate of reversal of the mutation -it indicates the degree to which a substance is mutagenic 1. 2 cultures are prepared of Salmonella bacteria that have lost ability to synthesize histidine 2. the suspected mutagen is added to the experimental sample only; rat liver extract (activator) is added to both samples 3. each sample is poured onto a plate of medium lacking histidine and incubated (only bacteria whose histidine-dependent phenotype has mutated back to hisitidine-synthesizing will grow into colonies) 4. colonies on both plates are compared, control may have few spontaneous, test plate shows an increase in the number of revertants if it is a mutagen and potential carcinogen

What can a typical genetic modification procedure (cloning) be used for?

-gene encoding protein for pest resistance is inserted into plant cells -gene encoding protein degradative enzyme to clean up toxic waste is inserted into bacteria cells -amylase, cellulase, and other enzymes prepare fabrics for clothing manufacture -human growth hormone treats stunted growth

Briefly describe the factors that influence the development of nosocomial infections

-genetic recombination: E. coli and the avian flu -evolution of new strains: V. cholerae -widespread use of antibiotics & pesticides: antibiotic resistant strains -changes in weather patterns: Hantavirus -ecological disaster, war, expanding human settlement: coccidiodomycosis, Ebola -animal control measures: Lyme disease, hantavirus -public health failure: diptheria, pertussis, measles

What are the characteristics of Salmonella and what causes most of the symptoms of it? How does that effect the time it takes to notice symptoms?

-gram-negative, facultative anaerobe, non-endospore-forming rods -normal in the intestinal tract -this invades mucosa and multiplies incubation of 12-36 hours then shows symptoms

What are the characteristics of Staphylococcus aureus and what causes most of the symptoms of it? How does that effect the time it takes to notice symptoms?

-gram-positive, round shaped -coagulates blood plasma -it's an entertoxin -produced when organism is allowed to incubate in food

What is the mode of action of soaps/detergents/quats? Provide example.

-have hydrophillic and hydrophobic ends, negatively charged organic surfactants which react with plasma mebrane

How does radiation cause induced mutations?

-ionizing: x-rays & gamma rays, cause the formation of ions that can oxidize nucleotides and break the deoxyribose-phosphate backbone -nonionizing: UV rays, cause thymine dimers, repaired by photoreactivation

What were Griffith's results while injecting mice with different strains of S. pneumoniae?

-live: dead mice -heat-treated: live mice -R strain live cells (no capsule): live mice -living R strain & heat treated dead cells of S strain: dead mice

What is dry heat? Provide examples.

-there is no steam and it kills by oxidation ex: flaming, incineration, hot-air sterilization

What is the mode of action of gaseous sterilants? Provide example.

-microbial and sporicidal gases used in closed chambers to sterilize items -denatures proteins and DNA by cross-linking to functional groups PRO: used in hospitals and dental offices on heat-sensitive material CON: dnagerous/hazardous to people, can be explosive, extrmeely poisonous, potentially carcinogenic ex: ethylene oxide

What is moist heat and what is it used for? Provide examples

-more effective than dry heat -used to disinfect, sanitize, and sterilize -denatures proteins ex: boiling, autoclaving, pasteuization, ultra-high-temperature sterilization

How does a microorganism gain access through the parenteral route?

-not a true portal -means by which the portal can be circumvented -deposit directly into tissues beneath the skin or mucous membranes

How does a microorganism gain access through mucous membranes?

-open to environment -respiratory tract is most common site of entry -GI tract -Genitourany tract -conjuctiva

What are organic growth factors? examples. How many of these do we need?

-organic compounds obtained from the environment -ex: vitamins, amino acids, purines, pyrimidines -cannot be synthesized by certain organisms -some need very few, others may require may more

How does the environment influence the effectiveness of a control method?

-organic materials: can interfere with penetration of antimicrobial agents -higher temperatures and acidic pH often make chemical more effectvie -temp: dependent chemical reactions

What are the two groups of organisms based on source of electrons?

-organotrophs: organic molecules -lithotrophs: inorganic molecules (minerals)

list the in order from most resistant to least resistant: -gram-negative -gram-positive -mycobacteria -virsues w/o envelopes -fungi -prions -cysts of protozoa -viruses w/ lipid envelopes -vegetative protozoa -endospores

-prions -endospores -mycobacteria -cysts of protozoa -vegetative protozoa -gram (-) -fungi -viruses w/o envelopes -gram (+) -viruses w/ lipid envelope

How does a microorganism gain access through the placenta?

-rare -pathogens can enter placenta and infect fetus

What are some ways to prevent nosocmial infections?

-reduce number of pathogens -infection control committees

Describe the 3 ways bacteria can be preserved for extended periods of time as stock culture.

-refrigeration: short periods of time (days-weeks) -deep freezing: -50 to -95 degrees C; stores for years; use cryoptotectants (antifreeze) ice crystals may form/poke holes in cell membranes -lyophilization: (freeze-drying): frozen (-54 to -72 C) & dehydrated in a vacuum; stores for decades; uses glycerol as antifreeze to slow down ice crystal formation

Name the portals of exit

-respiratory tract -GI tract -genitourinary tract -skin -blood

Describe the elongation stage translation of RNA into protein

-second tRNA binds to mRNA in the A site -amino acids of first and second tRNAs form a peptide bond -ribosome translocates one codon 3'

What are the characteristics of Vibrio cholera and what causes most of the symptoms of it? How does that effect the time it takes to notice symptoms?

-slightly curved, gram-negative rod with single polar flagellum -salty waters -produce cholera toxin which causes the host cells to secrete electrolytes -can lose 12-20 liters of fluid per day which causes shock, collapse, organ failure, and death

Define plasmid. Why are these important?

-small molecules of DNA that replicate independently, found in bacteria, archaea, and eukaryotes -not essential for normal metabolism, growth, or reproduction -diverse

How does a microorganism gain access through the skin?

-some pathogens can enter through opening on skin, others can burrow into or digest outer layers of the skin

What are possible limitations/challenges to Koch's postulates?

-some pathogens cannot be cultivated in a lab -some syndromes may be caused by more than one pathogen -some pathogens cause more than one disease -some pathogens cause disease only in humans

What do frameshift mutagens do? What are intercalating agents?

-squeeze into DNA strand, then expand DNA strand -molecules that insert themselves between adjacent bases

What do these suffixes mean? -statis (static) -cidal (side)

-statis: stopping growth of -cidal: killing

What are some ways that pathogens can damage the host?

-stealing host nutrients -causing direct damage immediately around infection -toxins which damage distally -hypersensitivity reactions

Describe the initiation stage translation of RNA into protein

-the 30S subunit binds 5' end of mRNA -translocates in 3' direction to first AUG -initiator tRNA binds to AUG in the P site -the 50S subunit joins to form the initiation complex

What is a frameshift mutation?

-the insertion or deletion of one or more nucleotide pairs -shifts the "reading frame" -affects all amino acids downstream from addition or deletion -frequently result in STOP codons

If given the codon (mRNA) for specific amino acids determine:

-the order of bases in the antisense strand of DNA (template strand - compl to mRNA) -the order of bases in the sense strand of DNA (coding strand - analogous to mRNA) -the anticodon for each specific amino acid (on tRNA - compl to mRNA)

What is meant by semi-conservative replication? How does the antiparallel form of DNA make this happen?

-the process of DNA replication in which each double-stranded DNA molecule contains one original strand and one new strand -5' > 3" -5' carbon end-phosphate -3' carbon end-hydroxyl

What is generation time? Why do generation times vary?

-time required for a cell to divide & its population to double -dependent on chemical & physical conditions -among species -can take 20 minutes up to 24 hours

Describe the termination stage translation of RNA into protein

-translation is terminated when the ribosomes come to a STOP or NONSENSE CODON -the ribosome and the mRNA are free to begin translation again

What is the historical importance of cholera? Why do these outbreaks still occur today?

-was huge problem because of lack of proper sanitation -1854-1855 epidemic 2 weeks, 600 deaths in London - still occur because of compromise of sanitation and sewage disposal systems (occurred in Haiti)

What is hydrostatic pressure? What are barophiles?

-water exerts pressure in proportion to its depth -B: live under extreme pressure

What takes place in catabolite repression?

-when glucose IS present E. coli will preferentially use glucose over all other sugars (lac operon is not present when glucose is avaliable) -needs help of activator because it is weak (CAP) -inducer = cAMP--> builds up in cell when glucose is not avaliable (when glucose is high, cAMP is low) -if CAP doesn't bind to lac promoter there is no transcription

Name 3 types of exotoxins. Provided examples

1. A-B toxins ex: Diptheria, Clostridium, Cholera, Botulinum, Anthrax 2. Membrane-disrupting toxins ex: Leukocidins, Hemolysins, Streptolysins 3. Genotoxins ex: Helicobacter pylori

What are the 5 chemical conditions necessary for bacterial growth?

1. CHNOPS 2. e- 3. energy 4. trace elements 5. organic growth factor

Differentiate between the 3 methods of disease transmission. Give examples.

1. Contact transmission -direct: requires close association between infected and susceptible host -indirect: spreads to a host by a nonliving object called a FOMITE -droplet: transmission via airborne droplets (w/in 1 meter) 2. Vehicle transmission -by an inanimate reservoir -waterborne, airborne, foodborne 3. Vectors -anthropods (fleas, ticks, mosquitoes) -transmit disease by either mechanical (anthro carries on feet), or biological (pathogen reproduces in vector)

What are the 5 classifications prokaryotes are divided into?

1. Obligate aerobes 2. Obligate anaerobes 3. Facultative anaerobes 4. Microaerophiles 5. Aerotolerant anaerobes

List and describe the 2 main methods for the selection of mutant organisms. Which use replica plating?

1. Positive (direct) selection detects mutant cells because they grow or appear different 2. Negative (indirect) selection detects mutant cells because they do not grow/perform a certain function -replica plating identifies mutants

What types of oxygen can be toxic to forms of life? (there are 4) Briefly describe them

1. Singlet oxygen - normal molecular oxygen that has been boosted to a higher energy state 2. Superoxide free radicals (or anions) - formed in small amounts during respiration of orgs that use O2 as final electron acceptor 3. Peroxide anion - within hydrogen peroxide that is produced in a reaction & microbes develop enzymes to neutralize it 4. Hydroxyl radical - most react form of oxygen and is formed in the cellular cytoplasm by ionizing radiation

What is the difference between the 4 biosafety levels? (relating to the agents)

1. agents are not associated with disease in healthy adult humans 2. agents that are associated with human disease but is rarely serious 3. agents that are associated with serious or lethal human disease 4. agents that are likely to cause serious or lethal human disease

What are: 1. psychrophiles 2. psychotroph 3. mesohphiles 4. thermophiles 5. hypertherophiles

1. cold-loving microbes 2. more common and are most likely to be encountered in low-temperature food spoilage 3. moderate-temp loving microbes 4. heat-loving microbes 5. extreme thermophiles (Archaea)

What 4 things must a pathogen do to cause disease in a host?

1. gain access to host at high enough numbers 2. adhere to host tissues 3. penetrate or evade host defenses 4. damage host tissues

Describe the 3 conditions that create opportunities for normal microbiota to cause disease

1. intro of normal microbiota into an unusual site in the body (S. aureus in cutes can lead to infection) 2. immune suppression (patients undergoing chemo have this) 3. changes in normal microbiota (CDIF)

How do you experimentally test Koch's postulates?

1. microorganisms are isolated from a diseased or dead animal 2a. microorganisms are grown in pure culture 2b. microorganisms are identified 3. microorganisms are inoculated into a healthy lab animal 4. disease is reproduced in lab animal 5a. microorganisms are isolated from this animal and grown in pure culture 5b. microorganisms are identified

What is the difference between the 4 biosafety levels? (relating to equipment/environment)

1. no special precautions; basic teaching labs 2. lab coat, gloves, eye protection 3. biosafety cabinets to prevent airborne transmission 4. sealed, negative pressure, "hot zone", exhaust air is filtered twice through HEPA filters

What are the 4 physical conditions necessary for bacterial growth?

1. temperature 2. pH 3. Osmotic pressure 4. Hydrostatic pressure

List Koch's postulates

1. the same pathogen must be present in every case of disease 2. pathogen must be isolated from the diseased host and grown in pure culture 3. pathogen from the pure culture must cause the disease when it's inoculated into a healthy, susceptible lab animal 4. pathogen must be isolated from the inoculated animal and must be shown to be the original organism

Explain how antibiotic resistance genes are used to locate a clone

Antibiotic resistance markers on plasmid vectors are used to identify cells containing the engineered vector or protein

Compare PCR to DNA replication

Both: move in the 5' to 3' direction Diff: PCR-strands separated by denaturing DNA-separated by enzymes PCR- primers single stranded DNA DNA- primers made of RNA

What are some examples of penetrating host defenses?

Capsules: impair phagocytosis Antigenic variation: pathogens alter their surface antigens Cell wall components Enzymes: digests, breaks down things Penetration into the host cell cytoskeleton: surface proteins produced by bacteria that rearrange actin filaments of the cytoskeleton

What does CHNOPS stand for?

Carbon Hydrogen Nitrogen Oxygen Phosphorus Sulfur

What chemicals interfere with H bonding that results in changes of acidity?

H+ and OH-

Differentiate between horizontal and vertical gene transfer

H: transfer of genes between cells of the same generation, donor cell contributes part of genome to recipient cell V: transfer of genes from an organism to its offspring, for permanent genetic change, DNA must be passed on to subsequent daughter cells & be associated with origin or replication

Define ID50 and LD50. What do each of these measure?

ID50: infectious dose for 50% of sample population (virulence of a microbe) LD50: lethal dose for 50% of sample population (potency of a toxin)

What is an example of a staphylococcal disease?

Impetigo: bullous or nonbullous (crusting sores) -nonbullous most common

Give examples of cell wall components that promote pathogenicity

M protein: resists phagocytosis, found on cell surface and fimbrae, also used for attachment Opa protein: outer membrane protein used in attachment, helps pathogens enter a cell, antigenic variation Waxy lipid (mycolic acid): resists digestion by phagocytes

What is an example of a streptococcal disease?

Necrotizing fasciitis: "flesh-eating" disease

What are obligate & facultative halophiles?

O: organisms that have adapted so well to high salt concentrations that they actually require them for growth (extreme) F: do not require high salt but are able to grow at salt concentrations up to 2% (halotolerant)

What type of therapy is common to all three types of food/water poisoning covered in class?

Oral rehydration therapy or solutions

Compare & contrast eukaryotic and prokaryotic genome structure.

P: -singular, circular chromosome -DNA floating in nucleoid region -haploid -efficient and compact -nonessential DNA --> plasmid E: -nuclear chromosome -more than one cell -linear and sequestered w/in nucleus -condensed into chromatin -diploid Similarities: extranuclear DNA of eukaryotes resemble chromosomes of prokaryotes

Where does transcription and translation occur in prokaryotes and eukaryotes?

P: cytoplasm E: nucleus

What is PCR?

Polymerase Chain Reaction -process of increasing small quantities of DNA for analysis; used for diagnostic tests for genetic diseases and detecting pathogens

What are resident and transient microbiota?

R: permanently colonize the host and do not cause disease under normal conditions, commensal, mostly found on skin & mucous membranes T: remain in the body for a short period, in the same region as resident, cannot persist in the body due to: competition, elimination, and chemical/physical changes in the body

What is a reservoir infection? What are 3 types of reservoirs & examples of each?

RI: continual sources of infection 1. human: carriers may have inapparent infections or latent diseases ex: AIDS, gonorrhea 2. animal: zoonoses are diseases transmitted from animals to humans ex: rabies, Lyme disease 3. nonliving: soil and water ex: botulism, tetanus, cholera

How does life with a biofilm contribute too dental carries?

S. mutans start performing plaque, those attract other cariogenic bacteria, caries penetrate from enamel into dentin caused by gram-positive rods and filamentous bacteria

What are the indirect methods of not physically counting cells?

Turbidity: measurement of cloudiness with a spectrophotometer Metabolic activity: amount of metabolic product is proportional to number of bacteria Dry weight: bacteria and molds are filtered, dried, and weighed; used for filamentous organisms Genetic materials: isolate DNA sequences of unculturable prokaryotes, used to eliminate the number of these microbes

What are the direct methods of counting microbial cells?

Viable cell count: -used to quantify ONLY living cells -cells are able to multiply -valuable in monitoring bacterial growth -used when cell counts are too low for other methods Direct microscopic count: -useful in determining total number of cells -does NOT distinguish between living and deal cells -volume of bacterial suspension placed on a slide -avg number of bacteria per viewing field is calculated

What is transformation?

a procedure in which cells can take up DNA from the surrounding environment

What is site-directed mutagenesis?

a targeted and specfic change in a gene

What is differential media? provide examples?

allows distinguishing of colonies of different microbes on the same plate; some media have both differential and selective characteristics ex: MacConkey agar: contains pH indicator to identify bacteria that produce acid from lactose fermentation; gram (-) blood agar: certain bacteria produce hemolysin to break down RBCs Mannitol Salt agar: discourages growth of competeing organisms; contains pH indicator that changes color if the mannitol in the medium is fermented to acid

What is the purpose of an anaerobe incubator/chamber?

allows manipulation of microbe in oxygen-free environment (impt for strict anaerobes)

If bacterial cells were given a sulfur source containing radioactive sulfur in their culture media, in what molecules would the sulfur be found in the cells?

amino acids, proteins, RNA, and DNA

__________ often stops because of insufficient nitrogen? What is nitrogen fixation? Why is it important?

anabolism when N2 is used directly from the atmosphere important because some organisms live cooperatively in symbiosis with the roots of legumes

Define biotechnology & recombinant DNA technology

b: the use of microorganisms, cells, or cell components to make a product (food, antibiotics, vitamins, enzymes) rDNA: the insertion or modification of genes to produce desired proteins

What is a continuous culture or system?

bacterial culture can be maintained; continuous exponential growth can be sustained by the use of chemostat; continually drips fresh nutrients in, releases same amount of waste product; never enter death phase

What are scientific applications?

bioinformatics, DNA fingerprinting

What is a vector?

carries new DNA to desired cells, must be able to self-replicate, plasmids and viruses can be used as vectors

What is a latent disease?

causative agent is inactive for at time but then activates and produces symptoms

Describe the effects of microbial control agents on cellular structures (cell wall, cell membranes, proteins, nucleic acids)

cell wall: heat-related methods interfere with integrity cell membrane: permeability is altered allowing cellular contents to leak out proteins: hydrogen and covalent bonds are broke nucleic acids: hydrogen and covalent bonds are broke

What are nucleotide analogs ?

chemicals that are structurally similar to the nitrogenous bases but have slightly altered base pairing properties

What is a colony? How is it different from a colony forming unit?

colony: a population of cells arising from a single cell or spore or from a group of attached cells CFU: when a colony results from short segments of a chain of bacterial clump; plate counts

Describe the bacterial growth curve, identify the events of each phase

consists of 4 phases: -lag phase: intense activity preparing for population growth but no increase in population -log phase: logarithmic, or exponential increase in population -stationary phase: period of equilibrium; microbial deaths balance production of new cells -death phase: population is decreasing at a logarithmic rate

Define pure culture. Why are these important?

contains only one species or strain in order to classify and identify unknown bacteria

Why are restriction sites important?

cut sequences of DNA and destroy bacteriophage DNA in bacterial cells

Define disinfection

destroying harmful microorganisms (not necessarily endospores)

Define antisepsis

destroying harmful microorganisms from living tissue

How does high pressure suppress microbial growth?

destroys microbes by denaturing proteins and altering cell membrane permeability

Briefly describe the Disk-Diffusion method

evaluates efficiency of chemical agents, filter paper disks are soaked in chemical and placed on a culture, look for zone of inhibition around disks.

What is a chemically defined media?

exact chemical composition is known ; fastidious organisms are those that require many growth factors provided in chemically defined media

What is a complex media? Provide examples

extracts and digest of yeasts, meat or plants; chemical composition varies batch to batch nutrient broth, nutrient agar, blood agar

What is the use of phosphorus?

for the synthesis of nucleic acids and the phospholipids of cell membranes

Identify & give the role of the Operator

found between the promote and the coding sequence of a gene repressor proteins bind here to turn off transcription

Define and describe generalized & specialized transduction

g: random bacterial DNA is packaged inside a phage and transferred to a recipient cell s: specific bacterial genes are packaged inside a phage and transferred to a recipient cell

What is agricultural applications?

genetically modified plants

What is the purpose of an anaerobic jar?

grow anaerobes on regular media; oxygen is chemically removed after culture plates are introduced and the contaminant is sealed

What is adhesion?

how almost all pathogens attach to host tissues

What causes plasmolysis?

hypertonic solutions, environments, or an increase in salt or sugar

What are inducible enzymes? What are repressible enzymes? Provide an example

i: not regularly produced, turned on in certain situations ex: B-galactosidase r: routinely synthesized, but can be shut off, generally involved in biosynthesis ex: amino acid synthesis

List & describe the 5 stages of infectious diseases.

incubation period: interval between initial infection and first signs and symptoms prodromal period: short period after incubation, early, mild symptoms period of illness: disease is most severe period of decline: signs and symptoms subside period of convalescence: body returns to its pre-diseased state

Define bacteriostatic

inhibiting or stopping growth, not killing, microbes

How does low temperature suppress microbial growth?

inhibits microbial metabolism, growth, and reproduction

What is a subacute disease?

intermediate between acute and chronic

Define asepsis

is the absence of significant contamination

How does osmotic pressure suppress microbial growth?

it causes plasmolysis

Could a pure culture of bacteria be obtained by the streak plate method if there were only one desired microbe in a bacterial suspension of billions? What type of technique would help isolate this microbe?

it is possible but this method works better when the organism to be isolated is present in large numbers relative to the total population. it would be better and more beneficial to use the selective media to kill of unwanted colonies, then use the streak plate to obtain the pure culture

Define commercial sterilization

killing Clostridium botulinum endospores from canned goods

Define sanitization

lowering microbial counts on eating utensils to safe levels

What are some predisposing factors for disease?

makes body more susceptible -gender -inherited traits -climate/weather -fatigue -age -lifestyle -nutrition -chemotherapy

Briefly describe the Use-Dilution test

metal cylinders are dipped in test bacteria and dried, cylinders are placed in disinfectant for 10 minutes at 20 C, then they are transferred to culture media to determine whether the bacteria survived treatment

What is the difference between minimum, optimal, and maximum growth temperature?

min: lowest temp at which the species will grow opt: temp at which the species grows the best max: highest temp at which the species will grow

Describe the streak plate method

most commonly used to get pure cultures, sterile inoculating loop (aseptic technique) is used for three separate streaks in different directions, each of which has less bacteria than the last. the last cells that were spread are far enough apart to grow isolated colonies and can be picked up with a loop and transferred

What are: neutrophiles acidophiles alkalinophiles

n: grow best in a narrow range around neutral pH ac: grow best in acidic habitats al: live in alkaline soils and water

What is the use of nitrogen?

needed for protein synthesis and used to form the amino group of the amino acids of proteins

What is an opportunistic pathogen?

normal microbiota that cause disease under certain circumstances

Describe DNA replication

one "parental" double strand molecule is converted into two identical offspring 1. supercoiling is relaxed (topoisomerase/gyrase) 2. 2 strands of parental DNA are unwound (helicase) 3. the strands separate one small DNA segment at a time 4. free nucleotides match up with exposed ends of single stranded parent DNA 5. parental DNA is unwound a bit further to allow addition of next nucleotides 6. as the replication fork moves along the parent strand, the new strands must grow in an opposite direction 7. DNA polymerase add nucleotides to the growing DNA strrand in the 5'-->3' directions (initiated by RNA primer) 8. DNA polymerase removes RNA primer

What is a slow infection?

pathogen replication and disease process occurs over long period of time (generally fatal)

How does antigenic variation help a pathogen evade host defenses?

pathogens alter their surface antigens and antibodies are then rendered ineffective

What is binary fission?

prokaryotic cell reproduction by division into two daughter cells; it doubles the number of cells each generation

Define exotoxin

proteins produced and secreted by bacteria, produced inside of bacterium (usually Gram +) and secreted or released during lysis... soluble in bodily fluids, usually enzymes which are specific for a structure or metabolic function in host cell

What is temperature's effect on proteins and membranes of cells and organelles?

proteins: denature membranes: -if too low, membranes become rigid & fragile -if too high, membranes become too fluid

Define sepsis

refers to bacterial contamination

Contrast microbiota & opportunistic microorganisms

remember that microbiota ordinarily do not cause disease but do so in a different environment and are present in the body in relatively large number

Define sterilization

removing or destroying ALL microbial life

Why is carbon so important? What is it's use?

required for microbial growth, it's the structural backbone of living matter use: needed for all organic compounds that make up a living cell

Differentiate among the terms endemic, sporadic, epidemic, and pandemic

s: disease that occurs only occasionally end: disease constantly present in population epi: disease acquired by many people in a given area in a short time p: worldwide epidemic

What are genome projects?

shotgun sequencing

What are therapeutic applications?

subunit vaccines, gene therapy, biofuels

What is selective media? provide example

suppresses unwanted microbes and encourages desired microbes/contain inhibitors ex: MacConkey agar for isolation of Gram-negative bacteria (contains CV)

Contrast symptoms, signs, and syndromes

symptom: subjective characteristics of disease felt only by the patient; may not be directly observable signs: objective manifestation of disease or measured by others; can be measured and observed syndrome: specific group of signs and symptoms that accompany a disease

What is an acute disease?

symptoms develop rapidly but disease lasts only a short time

What is a chronic disease?

symptoms develop slowly

What is the use of sulfur?

synthesizes sulfur-containing amino acids and vitamins such as thiamin and biotin

What is a closed or batch system?

takes place in a test tube or flask there is no new input of nutrient and no released of waste; population of cells increase in predictable fashion; follows pattern called growth curve

Define degerming

the mechanical removal of microbes from a limited area (washing hands)

What is osmotic pressure?

the pressure exerted on a semipermeable membrane by a solution containing solutes that cannot freely cross membranes

What is translation?

the use of mRNA as a template in the synthesis of protein, occurs within the ribosome

Why is hydrogen an important chemical factor?

there is an unlimited supply

Why is water so important for the growth of microorganisms?

they obtain almost all of their nutrients from surrounding water & their composition is 80-90% water

What is a biofilm?

thin, slimy layer encasing bacteria that adheres to a surface

How does desiccation suppress microbial growth?

this is the absence of water, so microorganisms cannot grow or reproduce but can remain viable for years

Understand the general purpose of Western blotting

to detect the protein product using specific antibodies

Define biocide (germicide)

treatments that kill microbes (mostly chemicals)

What is the use of reducing media?

used for cultivation of anaerobic bacteria; contains chemicals that combine O2, to deplete it; heated to drive off O2

Describe exponential (logarithmic) growth

when cells begin to divide and enter a period of growth or logarithmic growth. this is when cell reproduction is most active and generation time reaches a constant minimum. most metabolically active