MICROBIO 4-6
View the attached figure. What is the approximate DRT of the culture?
10 minutes
Oxidation is defined as the _____.
A.loss of electrons
How many molecules of ATP are produced per glucose molecule in the Krebs cycle?
B.Two
View the following figure of cultures growing in thioglycolate medium. Which culture represents a facultative anaerobic bacterium?
C
Eutrophication can occur in fresh and saltwater environments that receive too much nutrient runoff, leading to an initial overgrowth of algae, and ultimately an anaerobic environment as the algae die off. What type of metabolic process is involved in creating the anaerobic environment?
Fermentation
Which of these statements about fermentation is NOT true?
Fermentation is useful because an additional ATP can be produced in addition to those produced by glycolysis.
Which of these microbes would you expect to grow at the top in a thioglycolate tube?
Obligate aerobe
If a disinfectant is used on a work bench it is referred to as a(n) _____.
disinfectant
Salts and sugars work to preserve foods by ____.
high osmotic pressure
A phenol coefficient evaluation was performed on a new disinfectant. The procedure was as follows; a culture of Staphylococcus aureus was prepared and then separated into two aliquots. One aliquot was exposed to a phenol dilution for 7.5 minutes and the other aliquot to a dilution of the new disinfectant for 7.5 minutes. After the 7.5 minute incubation, each culture was quantified by the viable plate count method. The culture exposed to phenol was reduced to 5 cells/mL and the culture exposed to the new disinfectant was reduced to 10 cells/mL. Calculate the phenol coefficient for this new disinfectant.
0.5
A bacterial culture growing exponentially increases from 2 million to 8 million cells in 2 hours. The generation time for this culture is ___.
1 hour
View the attached growth curve plotted on a semi-log graph. The black square labeled "A" represents the time at which the culture is at 10 cells, the black square labeled "B" represents the time at which the culture is at 40 cells. Estimate the generation time of this culture.
1 hr
View the attached figure. What is the approximate DRT of the culture? 10^6 down to 60
10 minutes
What is the theoretical maximum number of ATP molecules that are produced by aerobic respiration if acetyl-CoA is used as the energy source?
12
If it takes 20 minutes at a temperature of 75 C for a population of bacteria to be reduced from 100,000 cells to 10,000 cells, ____.
20 minutes is the DRT at 75 C
A microbial culture contains 1 million cells. If it takes 25 minutes to kill all microbes in a culture, the TDT is ______.
25 minutes
Thirty-six colonies grew on nutrient agar from 1.0 mL of undiluted sample in a standard plate count. How many cells were in the original sample?
36
For a mesophile, the optimum growth temperature would be about ____ C.
37
For a thermophile, the minimum growth temperature would be about ____C.
42
Which of the following concentrations of ethanol is the most effective bactericide?
70%
Lactobacillus is a bacterium that produces lactic acid via fermentation. It is important in the production of yogurt. Which of the graphs best represents its growth pattern?
A
Outdoor freshwater environments contain many bacteria, and collectively they are capable of robust growth feeding on a variety of food sources. However, many of them are incapable of infecting humans, as human body temp is not ideal for their growth. Which of the following growth curves best represent these bacteria?
A
Pictured are PABA, the substrate for the enzyme dihydropteroate synthase, and the antimicrobial drug sulfanilamide, which is an inhibitor of dihydropteroate synthase. Based on the structures, by what mechanism does sulfanilamide inhibit dihydropteroate synthase?
A.Competitive inhibition
the most common glycolytic pathway is the ______ pathway.
A.Embden-Meyerhof-Parnas (EMP)
Which of the following statements about fermentation is TRUE?
A.Microbes can be differentiated according to the substrates they are able to or unable to ferment.
Which of the following statements about fermentation is TRUE? A.Microbes can be differentiated according to the substrates they are able to or unable to ferment. B.Microbes capable of fermenting are unable to perform aerobic respiration when oxygen is present. C.The most common gas produced as a waste product of fermentation is oxygen. D.Only prokaryotes are capable of fermentation.
A.Microbes can be differentiated according to the substrates they are able to or unable to ferment.
What is the final outcome of the ETS during aerobic respiration?
A.Oxygen is reduced, and becomes converted to water.
Competitive inhibition occurs when _____.
A.the inhibitor binds to the active site of the enzyme
Which of these is an adaption that halophiles use to survive in high solute environments?
Actively accumulate ions in the cytoplasm to balance out the salt concentration outside the cell.
Which of the following conditions can affect enzyme function?
All of the above
Which of these is the most effective method of sterilization?
An autoclave
The process of adding a phosphate group (phosphorylation) requires energy. Where does the energy come from when phosphorylating ADP to produce ATP?
An organic molecule
Which of the following terms is not matched correctly to its definition?
Antisepsis - removal of microbes on skin or tissue through gentle to firm scrubbing and the use of mild chemicals.
Which of the following statements is true about enzymes?
Apoproteins alone are nonfunctional.
Which technique would be used to prevent infection of a patient and healthcare practitioner?
Aseptic technique
Many human pathogens are adapted to grow ideally at human body temperature. Which of the following growth curves best represent these bacteria?
B
Some food spoilage organisms will spoil foods left out on the counter for too long. The best way to prevent their growth is to place the food into the refrigerator. Which of the following growth curves best represent these bacteria?
B
Which of the following statements about lipid catabolism is NOT true?
B.The NADH and FADH2 produced by beta-oxidation can be used to oxidize glucose molecules in glycolysis.
Which of these statements about the nitrogen cycle is TRUE?
B.The process of converting inorganic nitrogen gas into organic ammonium, nitrogen fixation, can only be performed by bacteria.
How many net ATPs can be made from one molecule of glucose in glycolysis?
B.Two
How is ATP generated using a proton motive force?
B.Via the flow of protons across a membrane bound enzyme that uses the energy from the proton motive force to phosphorylate ADP
An enzyme in the Krebs cycle, citrate synthase, can be inhibited by succinyl-CoA, which looks like its substrate, acetyl-CoA. This is an example of _____.
B.competitive inhibition
Oxygen has the most positive redox potential, and therefore ____.
B.more ATP is produced by aerobic respiration than by anaerobic respiration
Butyric acid fermentation _____.
B.produces butyric acid
In oxygenic photophosphorylation, the source of electrons is ____.
B.water
Which of these statements about generation times is NOT true?
Because all bacteria are prokaryotic, they all have very similar generation times.
Which of the following physical methods to control microbial growth works via the mechanism of protein denaturation?
Boiling or flowing steam
How are non-cyclic and cyclic photophosphorylation similar?
Both involve an ETS to create a chemiosmotic gradient in order to produce ATP
How are oxygenic and anoxygenic photosynthesis similar?
Both involve an ETS to create a chemiosmotic gradient in order to produce ATP.
Lactococcus lactis is a strictly fermenting organism. It is an important organism used in the production of butter and cheese. Which of the cultures represents the growth of L. lactis in thioglycolate medium?
C
In homolactic fermentation, what is the final electron acceptor?
C.Pyruvate
What is the fate of electrons in non-cyclic photophosphorylation?
C.Reduce NADP+ to NADPH
Aerobic respiration cannot occur under all of the following conditions, except for which one?
C.The cell uses the ED pathway to break down glucose instead of the EMP pathway.
Besides the formation of oxygen, how are oxygenic and anoxygenic photosynthesis different?
C.The source of electrons differs between these two types of photosynthesis.
Xenobiotics ____. A.are easy to degrade, which is why they can be left in the environment B.generally are not a concern to human health, since they are left far away from human life C.can be degraded by certain bacteria, which can be introduced to contaminated sites D.can only be cleaned up by removing the contaminated material and treating it in a facility
C.can be degraded by certain bacteria, which can be introduced to contaminated sites
In the following reaction, which molecule has become reduced? pyruvate + NADH → lactic acid + NAD+
C.lactic acid
Photoautotrophs use energy from _____ in order to fix ____.
C.light; carbon dioxide
Which of these pairs of terms are mismatched?
C.proteins - aminoacidases
A _____ uses glucose for both carbon and energy.
Chemoheterotroph
View the results of a disk diffusion test below. Which compound was the most effective?
Clorox
Industrial fermentation techniques can be used for the commercial production of _____.
D.All of the above
Which of the following statements about methanogenesis is NOT true?
D.Methanogenesis primarily occurs in soil environments.
Aerobic respiration differs from anaerobic respiration in which of the following respects?
D.The final electron acceptors are different.
Which of the following best describes the mechanism of rubbing alcohol?
Denature proteins and disrupts membranes.
A use-dilution test was performed on 4 disinfectants (A-D) with the following results. Disinfectant A: 60 tubes with no growth Disinfectant B: 59 tubes with no growth Disinfectant C: 55 tubes with no growth Disinfectant D: 50 tubes with no growth and 10 tubes with growth Which of the following is the best conclusion that can be drawn from these results?
Disinfectant A and B passed the use-dilution test.
Helicobacter pylori, a microaerophile, is a microbial cause of stomach ulcers. Which of the cultures represents the growth of H. pylori in thioglycolate medium?
E
Based upon the information provided, which of these disinfectant treatments is more effective, a higher concentration for a shorter time, or a lower concentration for a longer time?
Equally effective.
Which of these statements about fermentation is NOT true? A. Fermentation occurs in order to oxidize NADH so that NAD+ can be regenerated for subsequently oxidizing glucose via glycolysis. B. Fermentation requires the use of an organic final electron acceptor. C. Fermentation is useful because an additional ATP can be produced in addition to those produced by glycolysis. D. Fermentation does not involve the creation of a proton motive force to produce ATP.
Fermentation is useful because an additional ATP can be produced in addition to those produced by glycolysis.
Which of the following can be used to effectively sterilize a heat-sensitive solution?
Filtration
Which of the following is an example of a lyophilized product?
Freeze-dried survivalist meal package
Which of the following methods is used to preserve food by slowing the metabolic processes of foodborne microbes?
Freezing
Which one of these biocidal treatments would be effective on surgical tongs wrapped in foil?
Gamma rays
During the transition reaction and the Krebs cycle, 6 CO2 molecules are formed per glucose molecule. Where did the carbons for each CO2 molecule originate from?
Glucose
Growth at low temperatures is difficult because membranes become less fluid, and enzymes are not very active, making metabolism difficult. Which of the following is NOT an adaptation that allows for growth at low temperatures?
Heat generating enzymes are produced to work along metabolic enzymes.
Identify the catabolic reaction.
Hydrolyzing the disaccharide sucrose to produce the monosaccharides glucose and fructose.
Dry heat does not kill as effectively as moist heat. How can you increase the effectiveness of dry heat to match that of moist heat?
Increase the time of exposure
Which of the following methods would likely be used to sterilize a box of single-use examination gloves in a factory?
Ionizing radiation
Why might cells begin to die at a faster rate than new cells are made?
Lack of nutrients and an increase in cellular waste products.
At which stage of bacterial growth does cell division not occur?
Lag
At which stage of bacterial growth is cell division the most rapid?
Log
Which quantification method is most useful for water or food samples, when you don't expect there to be a lot of bacteria?
MPN
Which of the following statements about enzymes and substrates is true?
Many enzymes require help in the form of nonprotein helper molecules in order to properly function.
Which of the following methods would likely be used to sterilize a growth medium that contains ampicillin, a heat-sensitive antibiotic?
Membrane filtration
Which of the following is not used to preserve foods?
Microwaves
In the following reaction, which molecule has become oxidized? pyruvate + NADH → lactic acid + NAD+
NAD+
Are you able to leave milk out on the counter because it has been pasteurized?
No, pasteurization kills most organisms, but not all. If you left it out at room temperature it would eventually spoil.
Which of the following methods of controlling growth will not denature proteins?
Non-ionizing radiation
At the conclusion of glycolysis, the transition reaction, and the Krebs cycle, how many ATP molecules are produced per glucose molecule?
Not 2, not 6, maybe 4
Quorum sensing is important in biofilm formation because _____.
Not B, maybe A
View the attached figure. What is the TDP of the culture? 10^6 down to 60
Not enough information
Suppose you were working with a medical support team at a natural disaster and you had to sterilize some basic metal surgical instruments. Which of the following methods could achieve this?
Not soaking, maybe boiling
Consider the death curve of a Staphylococcus aureus culture. The arrow indicates when a 2% bleach solution is added. How would the death curve appear if the culture becomes sterilized?
Option D
Which of the following statements about the sulfur cycle are NOT true?
Oxidizing hydrogen sulfide is done by chemoheterotrophs.
What does the acronym "PPE" stand for?
Personal Protective Equipment
A _____ uses light for energy and carbon dioxide for carbon.
Photoautotroph
Which of the following methods when used properly is capable of sterilization?
Radiation
Which of the following methods of controlling growth are bacteriostatic?
Refrigeration
Which of these pairs of terms about the light-independent reactions is NOT matched properly?
Regeneration - glucose is produced using G3P
Which of the following is an advantage of the direct microscopic count?
Requires no incubation time.
While ____ is able to detoxify a reactive oxygen species, it also produces one, hydrogen peroxide.
Superoxide dismutase
As you know, high temperatures denature proteins, rendering them inactive. Which of the following is NOT and adaptation that allows for growth at high temperatures?
The DNA is rich in adenine-thymine base pairs, which are stronger than guanine-thymine base pairs.
Which of the following best describes the pattern of microbial death?
The cells in a population die at a constant rate.
Which of the following is the best definition of oxidative phosphorylation?
The energy released in the oxidation of electron carrier molecules is used to generate ATP via an electrochemical gradient.
Which of the following is the best definition of generation time?
The length of time needed for a population to double
Human cells require an environment that consists of about 0.9% salt to balance the solute concentration inside the cytoplasm or the cells will burst. Why are bacteria not particularly affected if placed in very diluted water?
The peptidoglycan cell wall protects the cells from bursting.
What is the main purpose of NAD+/NADH during glycolysis?
To carry high-energy electrons derived from glucose.
What is the purpose of the in-use test?
To determine if a disinfectant is contaminated with microbial growth.
Which of the following is NOT a direct method to measure microbial growth?
Turbidity
Which of the following statements about using turbidity to quantify bacteria is TRUE?
Turbidity is measured by transmitting a light beam through a liquid culture.
When is a disinfectant an antiseptic?
When it is used on your skin.
Coffee has a pH of approximately 5. What type of microbe can grow in your coffee?
acidophile
Which of the following terms describes a control procedure that kills a bacterium?
bactericidal
Which of the following pairs of terms is mismatched?
bacteriostatic — kills bacterial cells
In order for an organism to survive in an aerobic environment, it must ____.
be able to detoxify reactive oxygen species
Which pH is considered acidic?
below 7
Most bacteria reproduce by ______.
binary fission
Patients with indwelling catheters are susceptible to infections because ____.
biofilms can develop on catheters
Some yeasts divide by producing long extensions at one end of the cell that eventually detaches. This process of cell division is called ____.
budding
Haemophilus influenzae, a bacterial cause of pneumonia, prefers a higher concentration of carbon dioxide when growing, so it has to be cultured using a candle jar. This type of microbe is referred to as a(n) _____.
capnophile
The reactions involved in producing smaller compounds from larger and complex compounds are part of _____.
catabolism
A simple and rapid test to distinguish aerotolerant anaerobes from facultative anaerobes is to test for the enzyme ____.
catalase
One medium used to grow a chemoheterotroph has the following recipe. Glucose - 5 gAmmonium phosphate - 1 gSodium Chloride - 5 gMagnesium sulfate - 0.2 gPotassium phosphate - 1 g This type of medium is best described as a(n) ____ medium.
chemically defined
Which of the following is not a heavy metal disinfectant used to control growth of microbes?
chlorine
When grown on blood agar, bacteria that are capable of lysing red blood cells turn the agar clear. Bacteria that do not have this ability do not alter the color of the medium. This is an example of a(n) ____ medium
differential
Flaming the loop in the lab this is an example of __.
dry-heat sterilization
Photosynthesis starts when a photosystem absorbs the energy from light, and transfers the energy to _____.
electrons
Fastidious organisms require a large number of growth factors in order for proper growth. Thus, these organisms are typically grown on _____ media.
enriched
Shoyu is highly salty (often higher than 28%). What type of microbe can grow in shoyu?
halophile
Staphylococcus species can resist high salt concentrations, such as that found on human skin, but they do not require it for growth. These bacteria are referred to as ____.
halotolerant
B.Via the flow of protons across a membrane bound enzyme that uses the energy from the proton motive force to phosphorylate ADP
holoenzyme
Nitrites are added to food products because they _____.
inhibit endospore germination
Organic acids, such as benzoic acid, are added to food products because they _____.
inhibit metabolism of microbes
In the disk-diffusion method, ____ zone of inhibition around a filter soaked with a chemical indicates that the test bacterium is resistant to the chemical.
no
Which of these pairs of terms is mismatched?
phycobilins - lichen
Soap is a surfactant, and it works to prevent infection from microbes by _______.
physically removing microbes from your hands
Restaurants use high temperature water to wash eating utensils in order to lower microbial counts to safe public health levels. This is an example of ______.
sanitization
Phenylethyl alcohol agar inhibits the growth of gram-negative bacteria by altering their membrane permeability, resulting in cell damage. This is an example of a(n) ____ medium
selective
All media needs to be free of microbes, so you need to ____ media before you use it.
sterilize
Even the worst tattoo artist recognizes the importance of using tattoo needles that are free of contamination. In order to conform to this principle, these types of tattoo needles would have to be ______ prior to use.
sterilized
When using fluorescence staining to distinguish between live and dead cells, _____.
the dead cells appear red because the DNA can only be stained if the plasma membrane is significantly damaged
If foods/beverages are not sterilized by pasteurization, why do we pasteurize?
to increase the shelf life of a food or beverage.
