Micro Exam 2 questions
Why is alcohol effective against some viruses and not others
Alcohol denatures proteins by disrupting membranes and lipids in the lipid component of an enveloped virus but not in a nonenveloped virus
What is the advantage of the degeneracy of the genetic code
Allows for a certain degree of mutation
Identify the methods of action and preferred uses of halogens
Alters composition of cellular components. Ex. Chlorine gas- used to disinfect water, dairy equipment, utensils, glassware
What causes transcription of an inducible enzyme
An inducer initiates transcription of a gene
Justify the use of each of the following: anaerobic techniques, living host cells, candle jars, selective and differential media, enrichment medium
Anaerobic techniques- reduce oxygen to be able to grow anaerobic bacteria Living host cells-Used for bacteria that do not grow in artificial media (Mycobacterium leprae, syphilis spirochete) Candle jars- Consumes oxygens and provide for the high CO2 environment (capnophiles) Selective media-suppress the growth of unwanted microorganisms and encourage the growth of desired ones Differential media- easier to distinguish colonies of the desired organisms enrichment medium- used for preliminary isolation that favors growth of a particular microorganism
How would you isolate an antibiotic-resistant bacterium? An antibiotic-sensitive bacterium?
Antibiotic resistant bacterium to positive/direct selection an antibiotic sensitive bacterium to negative/indirect selection
Is Betadine an antiseptic or a disinfectant when it is used on skin?
Antiseptic when used on skin and a disinfectant when used on an object
LQ The absence of significant contamination is referred to as?
Aseptics
When does translation stop
At a stop codon also known as nonsense (UAA, UAG, UGA)
Define bacterial growth, including binary fission
Bacterial growth- growth in numbers not size binary fission- prokaryotic cell reproduction by division into two daughter cells
Describe effectiveness of boiling
Boiling kills vegetative forms of bacterial pathogens almost all viruses and fungi and their spores within about 10 mins. Not always are reliable sterilization procedure
What is the technical name for bacteria that require a higher-than-atmospheric-concentration of CO2 for growth?
Capnophiles
Name a use for each of the four elements (carbon, nitrogen, sulfur, and phosphorus) needed in large amounts for microbial growth
Carbon-structural backbone Nitrogen-DNA, RNA and protein synthesis (amino acids) Sulfur- synthesize sulfur-containing amino acids and vitamins such as thiamine and biotin Phosphorus-synthesis of nucleic acids and phospholipids of cell membranes. Found in energy bonds of ATP
What is quorum sensing?
Cell to cell chemical communication
Identify how and why the pH of culture media is controlled
Chemical buffers are used to control the pH of culture media because bacteria produce acids when cultured in a lab. Most bacteria grow between 6.5-7.5
Distinguish the chemically defined and complex media
Chemically defined- exact chemical composition is known Complex media- made of nutrients including extracts from yeasts, meat, plants, or digests of proteins. Exact chemical composition varies slightly from batch to batch
Analysis6 Clostridium and Streptococcus are both catalase-negative. Streptococcus grows by fermentation. Why is clostridium killed by oxygen, whereas streptococcus is not.
Clostridium lacks cytochromes, enzymes, catalase, and peroxidase. It's a strict/obligate anaerobe. It dies from oxygen, uses fermentation, turns lactic acid into energy. Streptococcus is aerobic, also lacks catalase, has peroxidase which neutralizes superoxide and hydrogen peroxide and allows them to survive in oxygen environments.
The usual definition of sterilization is the removal or destruction of all forms of microbial life; how could there be practical exceptions to the simple definition?
Commercial sterilization which is a limited heat treatment that is only high enough to destroy endospores of clostridium botulinum (only pathogenic, very harmful bacteria)
Compare the mechanisms of genetic recombination in bacteria
Conjugation Vertical gene transfer Transduction Transformation Horizontal gene transer Crossing over
The coins used in this demonstration were minted many years ago; why were more contemporary coins not used
Contemporary coins contain a lot less metal
Describe how osmotic pressure suppresses microbial growth
Creates a hypertonic environment that causes water to leave the cell, resembles desiccation (both methods deny the cell the moisture it needs for growth)
Describe the DNA replication, including the functions of DNA gyrase, DNA ligase, and DNA polymerase
DNA gyrase relaxes DNA DNA ligase makes covalent bonds to join DNA strands, Okazaki fragments and new segments in repair DNA polymerase proofreads and repairs DNA
Why is one strand of DNA synthesized discontinuously
DNA polymerase can only run 5' to 3' so it is done in fragments on the lagging strand.
What is the base pairing in DNA important
DNA would not be identical
How might increased UV radiation (due to decrease in the ozone layer) affect the Earth's ecosystem?
Damage human eyes, skin, and the DNA of exposed cells by the formation of bonds between pyrimidine bases
Explain how microorganisms are preserved by deep-freezing and lyophilization (freeze-drying).
Deep freezing- pure culture is placed in a suspending liquid and quick-frozen Lyophilization- quickly frozen and water is removed by high vacuum. The remaining powder like residue contains the surviving microbes.
Define disinfection
Destroying harmful microorganisms
Differentiate direct and indirect methods of measuring cell growth
Direct is a direct counting of cells or colonies. Indirect is based off of a number produced by a measure of something alternative to number.
Which is more likely to be used in a medical clinic laboratory, a use-dilution test or a disk-diffusion test
Disk-diffusion test is most used in a medical clinic laboratory because this is used to measure the effectiveness of specific antibiotics on certain microbes. A used-dilution test would be more appropriate in industrial uses because it measures the lowest amount of chemical needed in a solution to effectively kill microbes
Identify the methods of action and preferred uses of phenolic derivatives
Disrupt the plasma membrane and thereby denature the enzymes. They are used as disinfectant in an environmental surfaces, instruments, skin surfaces and mucus membranes
What characteristics make surface-active agents attractive to the dairy industry
Does not change taste, or color
What is the effectiveness of dry heat
Dry heat kills by oxidation effect, done by direct flaming (inoculating loop)
Why did encapsulated bacteria kill the mouse while non-encapsulated bacteria did not?
Encapsulated bacteria could not be digest by phagocytosis whereas the non-encapsulated bacteria could be.
Identify chemical sterilizers
Ethylene oxide
Why is it difficult to measure realistically the growth of a filamentous mold isolate by the plate count method?
Filamentous mold does not grow on agar but only on dead organic matter (saw dust). Secondly, the pour plate method measures number of colonies, but filamentous mold would form one large clump
Describe the formation of biofilms and their potential for causing infection
Form a thin, slimly encasing that adheres to a surface which protects the pathogens from antibiotics
Define genome
Genetic information in the cell
When both glucose and lactose are present, why will cells use glucose first
Glucose is more efficient and lactose is only used when glucose is not present
Are quats most effective agains gram-positive or gram-negative bacteria
Gram-positive
In what instances would the pour plate method be more appropriate than the spread plate method
Heat sensitive bacteria would be killed during the pour plate method but not the spread plate method.
How is microbial growth in canned foods prevented?
Heating-it denatures the proteins in the food and renders the bacteria harmless
Describe how high pressure suppresses microbial growth
High pressure alters the molecular structures of proteins and carbohydrates resulting in the rapid inactivation of vegetative bacterial. An advantage to this is they preserve the flavors, colors, and nutrient values of the products
One day a patient calls, alarmed that the hydrogen peroxide caused her wound to bubble. What would you tell the patient?
Humans have the enzyme catalase which breaks down hydrogen peroxide into water and molecular oxygen. The oxygen is causing the bubbles. The bubbles loosen debris and promotes healing.
What is the connection between the killing effect of radiation and hydroxyl radical forms of oxygen?
Hydroxyl radical forms of oxygen is a part of ionizing radiation because it can damage the DNA
How would one determine whether a microbe is a strict anaerobe?
If the microbe does not grow in the the presents of oxygen or resides at the bottom of a tube of solid growth medium
Describe how low temperatures suppress microbial growth
In some microbes low temperatures (refrigerator) will reduce metabolic rate so they can not reproduce or synthesize toxins (bacteriostatic). But, psychrotrophs grow at refrigerator temps and will alter the appearance and taste of foods over time.
Direct methods usually require an incubation time for a colony. Why is this not always feasible for analyzing foods?
Incubation is time consuming (24hrs-1week) so it is not suitable to measure foods
Why can the RNA transcript be used for translation
Introns have not yet been removed and the extrons have not been sliced together
Differentiate halogens used as antiseptics from halogens used as disinfectants
Iodine is used as an antiseptic by impairing protein synthesis and alters cell membranes forming complexes with amino acids and unsaturated fatty acids Chlorine is used as a disinfectant. its germicidal action is caused by the hypochlorous acid that forms when chlorine is added to water
How is a plastic filtration apparatus presterillized?(assume the plastic cannot be heat sterilized)
Ionizing radiation- high energy electron beams.
How does miRNA stop protein synthesis
It binds with the mRNA to form a double strand and then degrades the mRNA
Some lozenges intended to alleviate the symptoms of a sore throat contain phenol. Why include this ingredient?
It has a local anesthetic effect
In the direct microscopic count, despite its obvious disadvantages, is often used in estimating the bacterial population in dairy products. Why?
It takes very little time. Dairy products are a time sensitive matter and that must be taken into consideration when choosing what counting method to use
In mammals, some miRNAs hybridize with viral RNA. What would happen if a mutation occurred in the miRNA gene?
It would not be able to degrade the viral RNA
Explain how radiation kills cells
Kills cells by either ionizing or nonionizing. Ionizing: gamma rays penetrate deeply but require horse to sterilize large masses. Radicals kill organisms by reacting with organic cellular components, damaging them. Require more "hits" to kill it. Non ionizing: wavelength longer than ionizing (UV)- damages the DNA exposed cells by causing bonds to form between adjacent pyrimidine bases (usually thymines) Inhibit correct replication of DNA during cell reproduction.
If a technician were working with pathogenic prions, how would material leaving the lab be rendered noninfectious?
Lab should be under a sealed environment with negative pressure, HEPA filters on intake and exhaust air. Exhausted air is filtered twice.
Compare the phases of microbial growth, and describe their relation to generation time
Lag-intense metabolic activity preparing for growth but no actual growth Log- exponential increase in population because of binary fission (bacteria) mitosis (yeast) Stationary phase- amount of cells dying and being produced equal each other The death phase- population is decreasing at a logarithmic rate
List the advantages of glutaraldehyde over other chemical disinfectants
Less irritating and more effective than formaldehyde. Can be considered a sterilizing agent
Describe the effects of microbial control agents on cellular structures
Membrane- alternation to permeability (cellular contents leak and interfere with the growth of the cell) DNA and RNA are damaged and inhibit replication
If there is no good method for analyzing a product for its vitamin content, what is a feasible method of determining the vitamin content?
Metabolic Activity (in a microbiological assay, acid production is used to estimate the amount of vitamin present)
Natural selections means that environment favors survival of some genotypes. From where does diversity in genotypes come?
Mutations, transposition, and recombination.
Could Louis Pasteur, in the 1800s, have grown rabies viruses in cell culture instead of in living animals
No because viruses need a living host
If the space station in earth orbit suddenly ruptured, the humans on board would die instantly from cold and the vacuum of space. Would all of the bacteria in the capsule also be killed?
No, instead, they would loose their water content and be lyophilized.
Do bacteria reproduce during conjugation?
No, it is the transfer of genetic material but not creating a new cell due to reproduction.
Can a complex organism, such as a beetle, divide by binary fission
No, it would need to use mitosis for reproduction
Can you think of any reason why a colony does not grow to an infinite size, or at least fill the confines of the Petri plate?
Nutrient exhaustion
Explain how microbes are classified on the basis of oxygen requirements
Obligate Aerobes- require oxygen (only aerobic) Facultative anaerobes- Growth is better in oxygen (aerobic/anaerobic) Obligate anaerobes- Only anaerobic growth (no oxygen) Aerotolerant anaerobes- Only anaerobic but can occur with the presences of oxygen but do not use oxygen Microaerophiles- only aerobic growth in a low concentration of oxygen
Define obligate aerobes
Organisms that require oxygen to live
What should have been used to wrap the items instead of aluminum foil
Paper because aluminum is impervious to steam
If you wanted to disinfect a surface contaminated by vomit and a surface contaminated by a sneeze, why would your choice of disinfectant make a difference?
Phenolics can be used to disinfect the surface contaminated by vomit, Biguanides such as chlorhexidine can be used on the surface contaminated with sneeze. No single chemical is good for all applications. The derivative of phenol is reactive even in the presence of organic matterial whereas biguanides can only act on bacteria
How can mutations be repaired?
Photolyases- light repair enzymes- uses visible light to bring dimer back to original 2 enzymes Nucleotide excision repair- The repair of DNA involving removal of defective nucleotides and replacement with functional ones
Describe the functions of plasmids and transposons
Plasmids are self-replicating gene containing circular pieces of DNA Transposons are segments of DNA that can move from one region of a DNA molecule to another
Explain four direct methods of measuring cell growth
Plate count- counting the number of colony forming units on a solid culture medium (CFUs) Serial Dilutions- Series of dilution to get an easily countable number of bacteria Filtration- filtered through thin membrane whose pores are too small to allow bacteria to pass. Bacteria transferred to a nutrient medium where colonies form Direct microscopic count- Area of viewing window is determined and bacteria is counted. An average derived from the average number of bacteria per viewing field
Describe the effectiveness of pasteurization
Process of mild heating to kill particular spoilage microorganisms and pathogens. Thermoduric bacteria is left over but very rarely kills disease.
What is the role of the promoter, terminator, and mRNA in transcription
Promoter- starts transcription of RNA by RNA polymerase mRNA Terminator is where transcription ends mRNA is the product made during transcription
Why is it difficult to define psychrophile, mesophile, and thermophile?
Psychrophile, mesophiles and thermophiles all grow within ranges and are not rigidly defined
Classify microbes into five groups on the basis of preferred temperature range
Psychrophiles-cold loving Mesophiles-moderate loving Thermophiles-heat loving Extreme Thermophiles/hyperthermophiles- extreme hot (hot springs) Psychrotrophs- fridge temp (responsible for food spoilage)
Why are resistant (R) factors important in the treatment of infectious disease?
R factors are plasmids that make a pathogenic bacteria resistant to usual antibiotics. They confer upon their host cell resistance to antibiotics, heavy metals, or cellular toxins. This helps to identify which are pathogenic.
Describe the process of DNA replication
Relaxed by topoisomerase or gyrase. Unwound by helicase. Free nucleotides in cells cytoplasm are matched up to exposed base pairs Misplaced pairs are removed and replaced by replication enzymes Once aligned, new nucleotides bound by DNA polymerase
Describe the effectiveness autoclaving
Reliable sterilization. Steam under pressure to produce high temperature. Higher pressure = higher temperature. Preferred method for health care environments. Typically 15 psi and 121 degrees celsius
Define degerming
Removal of microorganisms in an area (modification of antisepsis- difference removal vs killing)
Explain pre-transcriptional regulation of gene expression in bacteria
Repression-Inhibits gene expression, default= on and induction- turns on transcription default= off
Which bacterium would theoretically be more likely to grow at refrigerator temperatures: a human intestinal pathogen nor a soilborne plant pathogen?
Soilborne plant pathogen
Analysis6 The E. coli was incubated with aeration in a nutrient medium containing two carbon sources. The following growth curve was made from this culture. Explain what happened at the time marked X. Which substrate provided "better" growth conditions for the bacteria? How can you tell?
Stationary phase is beginning as the first log phase finishes. During the stationary phase the death rate equals the new growth. The first one because the exponential growth rate is higher than the second.
LQ The removal or destruction of all forms of microbial life is called
Sterilization
LQ What treatment is intended to lower microbial counts on eating and drinking utensils to a safe public health level?
Sterilization
Define genomics
Study of genes and their function
When does transcription stop
Terminator
Define asepsis
The absence of significant contamination. Important in surgery to minimize contamination for instruments
Identify a way in which pathogens find it advantageous to form biofilms
The close proximity of microorganisms within a biofilm might also have the advantage of facilitating the transfer of genetic information (conjugation)
Why might primitive civilizations have used food preservation techniques that rely on osmotic pressure?
The high salt or sugar concentrations draw water out of any microbial cells that are present and thus prevent their growth
Describe how pure cultures can be isolated by using the streak plate method
The last cells to be rubbed off the loop are far enough apart to grow into isolated colonies which are then transferred to a test tube of nutrient medium to form a pure culture.
Why did a mixture of heat killed encapsulated bacteria and living non-encapsulated bacteria kill the mouse?
The live non-encapsulated bacteria were transformed by the dead encapsulated bacteria, so that they acquired the ability to form capsules and therefore cause disease.
Why is one strand of DNA "upside down" relative to the other strand? Why can both strands "face" the same way?
The nucleotide bases would not match up. 5' has phosphate on the end and OH is on 3' end. You can not add nucleotides to the 5'
What is specialized transduction?
The process of transferring a piece of cell DNA adjacent to a prophage to another cell.
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?
The radioactive sulfur would be found in the amino acids thus in proteins and DNA/RNA
Define sterilization
The removal or destruction of all living organisms
What causes transcription of a repressible enzyme
The repressor blocks the ability of RNA polymerase to initiate transcription of the repressed gene
Define genetics
The science of heredity
In what way would an anaerobic chamber resemble the Space Laboratory orbiting in the vacuum of space?
The space suits are connected to an air supply. This resembles the space laboratory orbiting in the vacuum of space
What is transduction?
The transfer of DNA from one cell to another by a bacteriophage.
What is generalized transduction?
The transfer of bacterial chromosome fragments from one cell to another by a bacteriophage.
How is it possible that a solution containing a million bacteria would take longer to sterilize than one containing half-million bacteria
There is more bacteria to kill
What is a hemolysin
They are exotoxins that cause destruction of red bloods cell
Why are hyperthermophiles that grow at temperatures above 100 degrees celsius seemingly limited to oceanic depths?
They are found at hydrothermal vents which reach around 121 degrees
Why were the pseudomonas less affected by the four chemicals shown in the figure
They are gram-negative so they are difficult to penetrate and are resistant to many antibiotics. They actively grow in a quat environment. Can only be stopped by the halogen group of disinfectant.
Other than controlling acidity, what is an advantage of using phosphate salts as buffers in growth media?
They are nontoxic and provide phosphorus which is an essential nutrient
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?
They produce enzymes like catalase and SOD to neutralize oxygen
How could E. coli acquire the Shiga toxin gene?
Through specialized transduction.
Define decimal reduction time
Time in mins in which 90% of a population of bacteria at a given temperature will be killed. Important in the canning industry
How would an empty, uncapped flask be positioned for sterilization in an autoclave?
Tipped position so the steam forces out the air, because steam is lighter in air.
Compare protein synthesis in prokaryotes and eukaryotes
Transcription takes place in the nucleus eukaryotes and translation takes place in the cytoplasm. In prokaryotes both transcription an translation occurs in the cytoplasm so the two can happen simultaneously
Why is turbidity more useful in measuring contamination of liquids by large numbers, rather than by small numbers of bacteria
Turbidity measures the cloudiness of the liquid, so small amounts of contaminant would not be picked up
Explain three indirect methods of measuring cell growth
Turbidity- uses a spectrophotometer to transmit a beam of light through the suspension that measures the percentage of transmission which relates to amount of bacteria in the tube Metabolic activity- assumes that the amount of certain metabolic product (acid/CO2) is in direct proportion to number of bacteria present. Dry weight- fungus is removed from growth medium, filtered to remove extraneous material and dried then weighed
Differentiate horizontal and vertical gene transfer
Vertical gene transfer is gene transfer for one generation to the next. Horizontal gene transfer is using the same generation and implementing it into a recipient cell.
Identify the appropriate used for surface-active agents
Washing hand, cleaning food-processing facilities, fighting gram-positive bacteria
Why is the tincture of Zephiran more effective that the aqueous solution
Water is needed for denaturation
Give a clinical application of genomics
West Nile Virus
Describe how filtration suppresses microbial growth
When a medium is filtered the microbes are too large to fit through the pores and are removed from medium. Used for heat sensitive products
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
When a microbe to be isolated is present in small numbers, its number must be greatly increased by selective enrichment before it can be isolated with the streak plate method
Explain the importance of osmotic pressure in microbial growth
When osmotic pressure is out of range, plasmolysis occurs (shrinkage of the cell's cytoplasm)
Describe the patterns of microbial death caused by treatments with microbial control agents
With each additional minute of exposure to microbial control agent, more microbes die. Shown as a straight line.
Could humans exist on chemically defined media, at least under laboratory conditions
Yes because chemoheterotrophs can survive on a chemically defined media and humans are chemoherterotrophs
Are bacteria capable of growing at a high osmotic pressure likely to be capable of growing in the mucus found in nostrils?
Yes because staphylococcus aureus found in the nasal passage have high tolerance to sodium chloride.
Would a chemical microbial control agent that affects plasma membranes affect humans
Yes, because humans have plasma membranes so it would also kill healthy cells
What is the advantage of semiconservative replication
You have one original DNA strand (conserved version) Its the template for the production of a second strand. Protects against mutation
Analysis6 Flask A contains yeast cells in glucose-minimal salts broth incubated at 30 degrees Celsius with aeration. Flask B contains yeast cells in glucose- minimal slats broth incubated at 30 degrees Celsius in an anaerobic jar. The yeasts are facultative anaerobes. a. Which culture produced more ATP? b. Which culture produced more alcohol? c. Which culture had the shorter generation time? d. Which culture had the greater cell mass? e. Which culture had the higher absorbance?
a. Flask A makes more glucose because it prefers oxygen and is in the presence of air (aeration), which provides for oxygen. b. Flask B because of fermentation, which lacks oxygen c. Flask A, because utilizing glucose in the presence of oxygen is more efficient. d. Flask A because it can grow more quickly due the presence of oxygen. The generation time is shorter. e. Flask A because it can absorb more nutrients as it is more efficient.
In what way is budding different from binary fission
binary fission is splitting into two smaller daughter cells which then becomes larger on their own while budding forms a small initial outgrowth which then enlarges and splits when it approaches the size of the parent cell
Why can translation begin before transcription is complete in prokaryotes but not in eukaryotes
both translation and transcription occur in the cytoplasm of prokaryotes so they can overlap. But in eukaryotes they occur in two different areas of the cell
What is the role of cAMP in regulating gene expression
cAMP builds up when there is a lack of glucose, it activates CAP which allows for lactose to be used for transcription
Identify the methods of action and preferred uses of heavy metals
components denature enzymes and other essential proteins. ex silver-sulfadiazine used as topical cream on burns
Surfactants (soaps / detergents)
decrease surface tension among molecules of a liquid
Identify the methods of action and preferred uses of alcohol
denatures proteins and dissolves lipids. Used to rub on skin to remove germs before injection
Identify the methods of action and preferred uses of biguanides
effective against gram-neg disrupts plasma membrane and used in skin disinfection (surgical hand scrubs)
What is the principle behind the Ames test?
exposure of mutant bacteria to mutagenic substances will cause new mutations that reverse original mutation
define phenotype
external manifestations of an organisms genetic makeup
Define genotype
genetic makeup of an organism
What chemicals are used to sterilize
glutaraldehyde, ethylene oxide
What chemical disinfectants can be considered sporicides
glutaraldehyde, hydrogen peroxide, peracetic acid
Explain how the type of microbe effects the control of microbial growth
gram-negative are harder to treat than gram-positive. Gram negative also have porins that are highly selective of molecules that they permit to enter the cell
The presence of endospores has an obvious effect on microbial control, but why are gram-negative bacteria more resistant to chemical biocides than gram-positive bacteria?
gram-negative are harder to treat than gram-positive. Gram negative also have porins that are highly selective of molecules that they permit to enter the cell
Define Genetic code
mRNA codeones and the amino acids they code
Describe protein synthesis, including transcription, RNA processing, and translation
mRNA is formed by transcription from DNA template, Extons are spliced by sRNPs, mRNA is brought into ribosomes tRNA bring complementary bases and amino acids to the mRNA and build a protein
Explain post-transcriptional regulation of gene expression
miRNAs bond with mRNA to make a double strand and destroy the unneeded parts of the mRNA
Define Thermal death time
minimal length of time for all bacteria in a particular liquid culture to be killed at a given temperature
How do mutagens affect the mutation rate?
mutagens increase spontaneous rate of mutation
Identify ways in which aerobes avoid damage by toxic forms of oxygen
presence of enzymes catalase and superoxide dismutase (SOD) allows toxic forms of oxygen to be neutralized; can use oxygen
Define Sanitization
removal of microbes from eating utensils and food preparation areas (intended only to lower microbial counts to safe public health levels)
Define Genes
segments of DNA encoding a functional product
Define chromosomes
structures containing DNA that cary the hereditary information. Contain Genes
Describe how DNA serves as genetic information
the DNA replications make it possible for the flow of genetic information from one generation to the next
Define Thermal death point
the lowest temp at which all the microorganisms in a particular liquid suspension will be killed in 10 mins
Interpret the results of use-dilution test and the disk-diffusion method
used diffusion: looking for number of cultures disk-diffusion: looking for zone of inhibition around bacteria
List the factors related to effective disinfection
using the right disinfection for the right circumstances, use appropriate concentration, nature of the material being disinfected, make sure disinfectant will easily make contact with the microbes
Compare conjugation between the following pairs: -F+ X F- -Hfr X F-
-F+ x F- transforms the F- into a F- -Hfr X F- just gives the F- partial F factor, but the F- remains F-
Differentiate biosafety levels 1, 2, 3, and 4
1- Basic microbiology teaching lab 2- Organism that present a moderate risk of infection. Open bench tops with gloves, lab coats, face and eye protection 3- labs intended for highly infectious air borne pathogens like Tuberculosis. Bio safety cabinets, neg pressurized, equip w/ air filters 4- "Hot Zone" very dangerous viruses, sealed environment w/i a larger building, under neg pressure, HEPA filters filtered twice, space suits are worn (ebola)
1. Will transcription of lac operon occur in the presence of lactose and glucose? 2. In the presence of lactose and the absence of glucose? 3. In the presence of glucose and the absence of lactose?
1. No 2. Yes 3. No
CAAE6 Assume that after washing your hands you leave 10 bacterial cells on a new bar of soap. You then decide to do a plate count of the soap after it was left in the soap dish for 24 hours. You dilute 1 gram of the soap 1:10^6 and plate it on heterotrophic plate count agar. After 24 hours of incubation, there are 168 colonies. How many bacteria where on the soap? How did they get there?
168 X 10^6 The bacteria could have been left on the soap by your hand and then divided by binary fission.
What is an Hfr cell?
A bacterial cell in which the F factor has become integrated into the chromosome; Hfr stands for high frequency of recombination
Why would a can of pork take longer to sterilize at a given temperature than a can of soup that also contained pieces of pork?
A can of pork is thicker while a can of soup has pork dispersed throughout the can. The solid pork is heated unevenly because of the uneven distribution of moisture
Define antisepsis
A chemical method for disinfection of skin or mucous membrane
Iodophor
A combination of iodine and an organic molecule, from which the iodine is released slowly. Have antimicrobial activity of iodine, but do not stain and are less irritating.
What is a phage?
A method of identifying bacteria using specific strains of bacteriophages.
What is an F+ cell?
A plasmid found in the donor cell in bacterial conjugation.
Define operon
A set of operator and promoter sites and structural genes they control
Given a shallow pan and a deep pot with the same volume, which would cool faster? Why?
A shallow pan because it has a greater surface area which allows for faster cooling time
Tincture
A solution in aqueous alcohol
Define biocide/germicide
A substance capable of killing microorganism except endospores
Define bacteriostasis
A treatment capable of inhibiting bacterial growth. If you remove it, bacteria can resume growth
What is a bacteriophage?
A virus that infects bacterial cells
Define colony
A visible mass of microbial cells arising from one cell or from a group of the same microbes
Oligodynamic action
Ability of small amounts of a heavy metal compound to exert antimicrobial activity
