Micro exam 2

A suffix used to describe a killing action would be

-cidal.

You are determining the number of colony forming units (CFUs) for Susan, who has a urinary tract infection (UTI). You added 1 mL of Susan's urine sample to 99 mL of diluent, and spread 0.1 mL of that dilution on a culture medium. After appropriate incubation, you count 143 colonies on the plate. What was the concentration of bacteria in the original urine sample?

1.43 x 105 cells/ mL

In a one D process, how many D values would it take to reduce a population of 1010 cells to one survivor?

10

A pure culture in exponential growth phase has a bacterial concentration of 6.4 x 108 cells/ml. If the bacterium has a generation time of 1 hour, how long ago was the cell concentration 8.0 x 107 cells/ml?

3 hours

A urine sample with more than 100,000 organisms is considered indicative of infection. A urine sample containing 5,000 bacteria, with a generation time of 30 minutes, sits for 3 hours before finally being assayed. How many bacteria will then be present within the sample?

320,000

The optimal temperature for most human pathogens might be expected to range from

35-40°C.

If a process kills 90% of the organisms per minute, how many minutes would it take to kill all organisms when starting with 100,000 organisms?

6 minutes

Which is true of competitive inhibition?

A sulfa antibiotic is a competitive inhibitor.

The readily usable energy currency of cells is _____.

ATP

Consider how an aerobically respiring bacterial cell uses glycolysis, the TCA cycle, and oxidative phosphorylation to break apart and oxidize glucose. What are the three main benefits these central metabolic pathways yield to the cell?

ATP, reduced electron carriers, and precursor metabolites.

You take spectrophotometer absorbance readings of a culture of E. coli cells growing in tryptic soy broth (TSB) at 2, 4 and 6 hours. Your absorbance readings clearly indicate a lag phase, a log phase, and a stationary phase. You come back in and take additional readings at 8, 10, 12, 14, and 16 hours, but the absorbance number remains the same. Shouldn't it start coming down as the closed batch culture enters death phase? What's the most likely explanation for what is happening?

Absorbance indicates cell number, but does not differentiate between live dead cells. The presence of dead cells keeps the absorbance high even into the death phase.

Which of the following processes generates the greatest amount of energy?

Aerobic respiration

A halophilic, aerobic mesophile has a generation time of 20 minutes. You place 1x104 of these organisms on an appropriate solid medium, and incubate the plate for 100 minutes. Select the FALSE statement.

After incubation, a colony on the plate contains 5 x 104 cells.

A microbe is discovered growing near a deep sea thermal vent. When researchers bring a sample up to the surface and try to grow it in a lab at room temperature in a regular incubator, they are unsuccessful. Why?

All of the answer choices are correct.

Microbial death rates may be affected by

All of the answer choices are correct.

To reduce or eliminate disease-/spoilage-causing organisms, food is often treated with

All of the answer choices are correct.

Chemical germicides

All of the answer choices are true.

Which is (are) true regarding organic acids?

All of the answer choices are true.

Please select the TRUE statement regarding preservation of perishable products.

Bacterial resistance to some of the chemicals included to perishable products has been reported.

A worker in a cheese-making facility argued that whey, a nutrient-rich by-product of the process, should be dumped into a nearby pond to serve as fish food. Is this a good idea or a bad one, and why?

Bad idea—bacteria would thrive on this rich nutrient source and multiply, using the oxygen in the water to harvest the energy from the whey. Without the oxygen, the fish will die.

Chemolithotrophs near hydrothermal vents support a variety of life forms. Why is this analogous to photosynthetic microbes supporting life forms closer to the surface of the planet?

Because all life forms need some energy source, electron source, and carbon source. Chemolithotrophs fix inorganic carbon and, if consumed by other microbes, could serve as sources for all three requirements for life. This is very similar to the role that photosynthetic microbes play in the top levels of the oceans/lakes.

Which of the statements about biofilms is TRUE?

Biofilms may protect organisms against harmful chemicals.

You are studying the metabolism of the phototrophic green sulfur bacterium Chlorobaculum tepidum and realize that it is running a reversed TCA cycle! How do you explain this observation?

C. tepidum is using the reversed TCA cycle to fix carbon dioxide.

Please select the TRUE statement regarding metabolic processes.

Catabolic processes harvest the energy released during breakdown of compounds to synthesize ATP.

Please select the CORRECT statement regarding catabolism and anabolism.

Catabolism breaks down compounds to release their energy; anabolism uses energy to make compounds.

Scientists isolated a new species of bacteria growing in sediments collected from a 63 meter deep site at the bottom of Lake Washington in Seattle This species, named Labrys methylaminiphilus, is capable of obtaining its carbon and energy needs from methylamine (CH3NH2), a derivative of ammonia (NH3) in which one H atom is replaced by a methyl (CH3) group. L. methylaminiphilus grows at a temperature range of 10-35°C, with optimal growth at 28-30°C, and a pH range of 4.0-9.5, with optimal growth at 5.0-7.0. Because methylamine is a single carbon compound resulting from the breakdown of decaying organic matter, methylotrophic ("methyl-feeding") bacteria like L. methylaminiphilus play an important role in carbon cycling in lake sediments and other environments. Consider the growth of L. methylaminiphilus on methylamine. How would you classify this species based on its metabolism?

Chemoorganoheterotroph

Which pair is correctly matched, regarding electron transport carriers in eukaryotes?

Complex III - cytochrome bc1 complex

Which of the following concerns would lead a user to wash an item after it had been treated with a germicide?

Corrosive residue left after treatment.

Please select the INCORRECTLY matched pair.

D-value - time to destroy 10% of microbes present.

During which phase of the bacterial growth curve does the total number of viable (live) cells decline?

Death

Choose which of the following best describe the difference between a disinfectant and an antiseptic.

Disinfectants are antimicrobial chemicals used on inanimate surfaces or objects to remove most of the pathogenic microorganisms. Antiseptics are antimicrobial chemicals that can be used on skin or tissues to achieve the same result.

Which are essentially equivalent treatments?

Dry 200°C heat for 1.5 hours; wet 121°C heat for 15 minutes

Which of the following is NOT common to aerobic respiration, anaerobic respiration, AND fermentation?

Electron transport chain

Which of the following is (are) considered when selecting a germicidal chemical?

Environmental impact, toxicity, cost AND compatibility with the material being treated.

The TCA cycle produces

FADH2, NADH, and precursor metabolites.

100% ethanol is twice as effective as 60% ethanol at controlling bacteria.

False

Aldehydes can be used to disinfect superficial wounds.

False

Cold temperatures and freezing are very effective in killing bacteria.

False

Competitive inhibition usually involves both substrate and inhibitor competing for binding at the allosteric site.

False

Differential media only allow certain bacteria to grow.

False

Dry heat takes a much shorter time to sterilize material than wet heat.

False

Enzymes are changed by the reaction as they raise the activation energy.

False

Freezing is an effective means of destroying bacteria.

False

HIV is highly resistant to antimicrobial chemicals and requires lengthy exposure to these products in order to be destroyed.

False

Handwashing with regular soap removes all normal microbiota from the skin.

False

Heat treatment is an effective method for sterilization or disinfection of all materials.

False

Hydrogen peroxide may be used as a sterilant on living tissue.

False

In Gram-negative bacteria, the electron transport chain involved in respiration is located in the lipopolysaccharide layer.

False

In microbiology, growth usually refers to an increase in size of the bacteria.

False

Measures to prevent prion contamination of healthcare settings have been in place for the past several decades and fully control the risk.

False

Microwaves kill microorganisms directly.

False

One would expect most strict anaerobic organisms to have superoxide dismutase.

False

Pasteurization results in the sterilization of food products.

False

Prions are easily destroyed by common sterilization procedures.

False

Regarding use of heat to control microbial growth, dry heat at lower temperatures is as effective as moist heat at the same temperature.

False

Sterilization is the destruction of all living microbes from a surface by physical or chemical means.

False

The Calvin cycle produces six ATP for every six turns of the cycle.

False

The change in free energy of a reaction varies.

False

The endospores of Pseudomonas make that organism very difficult to kill.

False

The terminal electron acceptor in aerobic respiration is water, which is broken down to hydrogen and oxygen.

False

There are five stages of growth in an open system of culture.

False

Fermentation is sometimes used as a means of slowing food spoilage. Why would fermentation lead to this outcome?

Fermentation will lead to production of acidic by-products, dropping the pH of the food below a level that bacteria can tolerate.

How do chemolithotrophs acquire energy?

From inorganic compounds

What is the effect of poisons such as mercury in antimicrobial products? Recall that mercury oxidizes the S-H groups of the amino acid cysteine in proteins, converting it to cystine.

Irreversible non-competitive inhibition—the mercury binds to an allosteric site on the enzyme and permanently changes the shape of the active site, so that the enzyme becomes nonfunctional.

Which of the folllowing is TRUE about agar?

It has chemical and physical properties that make it almost ideal for solidifying media.

Select the FALSE statement regarding hydrogen peroxide.

It immediately kills all bacteria when applied to a wound.

Which is TRUE of peptone?

It is a hydrolysate of proteins used in growth media.

Clostridium paradoxum grows optimally at 55°C, pH 9.3; it will not grow in the presence of O2. Please select the TRUE statement about this organism.

It is an obligate anaerobe.

Which is TRUE of iodine?

It is usually found as tinctures or iodophors.

What would true about an organism called Bacillus fastidiosus?

It might be expected to be very strict in its growth requirements.

Which of the following about heat treatment is FALSE?

It produces toxic byproducts.

Select the TRUE statement regarding fermentation.

It uses an organic molecule as the final electron acceptor.

During which phase of the bacterial growth curve does a bacterial population become much more resistant to harmful conditions?

Late log phase

In the electron transport system

NADH donates electrons "upstream" of where FADH2 donates electrons.

A student argued that aerobic and anaerobic respiration should produce the same amount of energy. He argued that both processes are essentially the same—only the terminal electron acceptor is different. What's wrong with his argument?

Not all electron acceptors are the same—some are closer in terms of electronegativity to their high-energy electron carrier molecules (e.g., NADH) than others, and this impacts the amount of produced energy. Oxygen has the highest electron affinity of the terminal electron acceptors used.

Experiments designed by ______ suggested that living cells caused the fermentation of sugar to produce alcohol.

Pasteur

Lister developed his ideas on prevention of infection during medical procedures after studying the work of

Pasteur.

Which of the following is NOT a sterilization method?

Pasteurization

Which of the following is/are not (a) sterilization method(s)?

Pasteurization

You are working in a clinical laboratory in a hospital setting. You're handed a throat swab from a patient. You are told specifically that the physician is only interested in the presence and type of Gram positive cells. Identification isn't the main goal here—just a first step to work towards determining what Gram positive cells might be there. What might you do first to go about working towards this goal?

Perform a Gram stain on the patient's sample.

A common environmental organism that may even grow in certain chemical disinfectants is

Pseudomonas aeruginosa.

Which would be most effective against Pseudomonas?

Radiation

The scientist that contributed most to the development of pure culture techniques was

Robert Koch

Hexachlorophene has been particularly effective against

Staphylococcus aureus.

Assuming strict adherence to recommended protocols, which of the following temperature treatments achieves sterilization?

Steam autoclaving

A physician sends a fecal sample to your lab, and wants to know if there are lactose fermenting microbes in it. How might you determine if these microbes are present or not from this mixed-microbe specimen?

Streak the sample for isolation on a MacConkey agar plate (which contains lactose and a pH indicator that turns pink when acid byproducts are present).

Please select the CORRECT definition of photophosphorylation.

Synthesis of ATP using the energy of a proton motive force created by harvesting radiant energy.

How would cellulose-degrading bacteria in the rumen (stomachs) of a cow benefit the animal?

The bacteria would produce, secrete, and incorporate organic molecules as they obtain energy from the cellulose in grass and replicate. The cow could then digest both the secreted organic molecules AND the bacteria that synthesized them.

You are a microbiologist working for a pharmaceutical company and discover a new secreted metabolite that can serve as a medication. Your company asks you to oversee the production of the metabolite. Which of the following does NOT need to be considered if you need to grow 5,000 liter cultures of bacteria for the purpose of harvesting the metabolite they secrete?

The death rate of the bacteria after stationary phase is complete.

You are culturing a new bacterium in the laboratory. You cannot find any glucose it the lab when you are making growth medium, so you decide to use honey instead. You add twice as much honey than is called for in the medium recipe, because you want to give the organism the best opportunity or growth. To your surprise, the organism does not grow on your modified medium. Select the most likely explanation.

The growth medium became hypertonic with the addition of so much honey; the bacteria underwent plasmolysis and died.

Please select the FALSE statement regarding the central metabolic pathways.

The transition step and TCA cycle are repeated four times to yield ATP, reducing power, and three different precursor metabolites.

Which is TRUE of HAIs?

They are acquired by susceptible people in the hospital.

Which statement regarding phenolics is TRUE?

They denature proteins and destroy cytoplasmic membranes.

Which of the following are TRUE regarding trace elements?

They include zinc, copper, and manganese AND they may be needed for enzyme function.

Which of the statements regarding chemoorganoheterotrophs is/are CORRECT?

They use preformed organic molecules as a carbon source AND as an energy source.

Why do cells degrade sugar?

To gain energy.

A single bacterial cell may multiply to form a visible colony on a culture medium.

True

Boiling is very effective at removing most common waterborne pathogens.

True

Both glycolysis and the pentose phosphate pathway oxidize glucose to pyruvate.

True

Cells must secrete enzymes that degrade macromolecules into their subunits before they can use these compounds.

True

Generally, heavy metals, except silver, have been proven to be too toxic for use on human tissue and are no longer used medically.

True

H2S and NH3 may be used by some prokaryotes as energy sources.

True

In fermentation, the only ATP produced was during glycolysis and the fermentation reactions usually result in converting NADH to NAD.

True

It is assumed that every colony observed on a streak plate arose from a single bacterium.

True

Organic acids, such as benzoic acid, are often added to foods to prevent microbial growth.

True

Prokaryotes are the only organisms able to use atmospheric nitrogen as a nitrogen source.

True

The TCA cycle must "turn twice" in order to complete the oxidation of one glucose molecule.

True

The government agencies that regulate germicidal chemicals are the Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA).

True

The more bacteria one starts with, the longer it will take to kill them all.

True

The more bacteria present on or in something, the longer it takes to kill them all.

True

The production of ATP via the electron transport system, in either eukaryotes or prokaryotes, requires the use of a membrane.

True

Upon heat treatment, bacteria die at a constant proportion.

True

Which of the following methods sterilizes the materials?

Ultrahigh-temperature (UHT) method

You are in charge of water quality for your city's water treatment plant. Which is the most efficient and cheapest method of determining the number of viable (living) bacteria in the water coming out of your plant?

Using membrane filtration followed by placing the membrane in a growth medium for colony counts after incubation.

MacConkey agar is

a selective and differential medium.

Oxygen serves as the terminal electron acceptor in

aerobic respiration.

Organisms that are indifferent to the presence of oxygen and do not use it are

aerotolerant anaerobes.

The solidifying agent used most successfully in bacterial nutrient media is

agar.

A sterile item is free of

all viable microbes, endospores, AND viruses.

Biosynthetic reactions that require energy for the conversion of molecular subunits into larger molecules are called

anabolic reactions.

The linking of N-acetyleglucosamine, N-acetylemuramic acid, and tetrapeptides is a(n) ______ reaction that ______ ATP.

anabolic; requires

A culture of E. coli is growing on glucose salts agar (GSA), a chemically defined medium that contains glucose as its sole carbon source. E. coli utilizes the glucose for both its energy and carbon needs. During metabolism, it uses precursor metabolites of its central metabolic pathways and ATP to build up the biological macromolecules needed to make cell components. These biosynthetic reactions are best described as ______.

anabolism

Most enzymes

are specific, typically recognizing a single or a few substrates.

The term "precursor metabolite" refers to molecules that

are used in biosynthesis.

High concentrations of salt and sugar in foods

are useful in preserving the food AND tend to draw water out of a cell.

In the cultivation of microaerophilic and anaerobic bacteria,

atmospheric oxygen in a(n) candle/anaerobe jar is converted to water.

Organisms that use CO2 as their source of carbon are called

autotrophs.

Prokaryotic cells divide by a process known as

binary fission.

Products that limit pH changes are often incorporated into media and are referred to as

buffers.

Mercury in mercurochrome inhibits growth

by oxidizing the sulfhydryl groups in cysteine AND by changing the shape of proteins.

Gamma irradiation

can be used to either sterilize or pasteurize, depending on the dose of radiation.

One of the first chemicals used by Lister to prevent surgical infections was

carbolic acid.

Ethylene oxide is a very effective microbial control compound. However, its use is somewhat risky because it is both explosive and ______.

carcinogenic

A culture of bacteria is breaking down sugars to yield energy. This is best described as ______.

catabolism

Enzymes act as

catalysts.

Quaternary ammonium compounds are

cationic detergents that help wash surfaces.

The small, non-protein molecules that can be readily separated from an enzyme and are responsible for transfer of atoms from one molecule to another are referred to as

coenzymes.

In prokaryotic cells, the electron transport chain (ETC) is located in the ______, whereas in eukaryotic cells, the ETC is located in the ______.

cytoplasmic membrane; inner membrane of mitochondria

Ultraviolet radiation at the bactericidal wavelength destroys bacteria by

damaging nucleic acid.

Commercial canning processes

destroy Clostridium botulinum spores, are especially needed on low acid foods, AND are 12D processes (designed to kill 1012 endospores).

The use of the suffix "ase" on a word denotes a(n)

enzyme.

Studies done by Buchner showed that ground-up yeast cells were able to convert sugar to alcohol. The components of the mixture that were responsible for this transformation were

enzymes.

In the growth curve of a bacteria population, the bacteria are rapidly increasing in number in the

exponential (log) phase.

Streptococcus pneumoniae lacks an electron transport chain. Therefore, S. pneumoniae generates ATP via ______.

fermentation

Pyruvate can be metabolized along two major routes. They are

fermentation and respiration.

Agar replaced gelatin as the solidifying agent for media because

fewer bacteria can break down agar compared with gelatin.

In eukaryotic cells undergoing respiration, protons are pumped

from the mitochondrial matrix to the intermembrane space.

The most common starting pathway for the breakdown of sugars is

glycolysis.

Medically important bacteria are often

grown on agar containing blood AND grown at 37°C.

Small organic molecules that must be provided to bacteria in order for them to grow are called

growth factors.

Boiling is not reliable for sterilization because

heat-resistant endospores are unaffected.

The autoclave treatment may be monitored by

heat-sensitive tape AND heat-resistant endospores of Geobacillus stearothermophilus.

Organisms that use organic molecules as their source of carbon are called

hetertrophs.

Your brother has a bacterial infection. He tells you he going to the gym where he plans to sit in the sauna for an hour. He thinks that this will cure his infection, because the heat in the sauna will denature the enzymes of the bacteria making him ill. You are a nursing student who is currently studying microbiology. You tell him that

his plan won't work; homeostasis will keep his body temperature constant even in the sauna, so the bacteria (and his normal microbiota and body cells) will not be impacted.

Oxidation of proteins is achieved most readily

in a hot air oven.

The mutual interaction of substrate and enzyme is described as a(n)

induced fit.

The most important function of nitrites in processed foods is to

inhibit the germination of Clostridium botulinum endospores.

Moist heat kills microorganisms by

irreversible denaturation of proteins.

Late log phase of the bacterial growth curve

is characterized by the production of secondary metabolites.

Free energy

is the amount of energy gained by breaking bonds of a chemical.

Proton motive force

is used to synthesize ATP.

Glutaraldehyde

is very good for use on heat-sensitive medical items.

Ethylene oxide is a gas that

is very useful for sterilizing heat- or moisture-sensitive items.

When doing experiments with bacteria,

it is best to use bacteria from the same stage of growth.

Hand washing with plain soap is very useful in controlling spread of microorganisms because

it is very effective at the mechanical removal of microorganisms.

The prefix photo- in the term photoautotroph indicates that an organism will make use of ______ for energy purposes.

light

The transition step

links glycolysis to the TCA cycle.

In a rapidly multiplying bacterial population, cell numbers increase

logarithmically.

Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur may be considered

major elements.

In nature, bacteria

may adhere to surfaces by means of pili and slime layers.

Anoxygenic photosynthetic bacteria

may obtain electrons from H2S.

Glycolysis

may occur under aerobic or anaerobic conditions.

Liquid media containing heat-sensitive components would best be sterilized by

membrane filtration.

A hot tub (with a water temperature of 104°F or 40°C) would most likely contain

mesophiles.

The lag phase of the bacterial growth curve is characterized by

metabolically active cells.

The general term used to describe the anabolic and catabolic reactions in a cell is

metabolism.

An atom that has a lower affinity for electrons than another is ______ than the other.

more electronegative

Mycobacterium leprae is typically found infecting the ears, toes, and fingers of its host due to its

need for cooler temperatures.

Alcohols are not reliably effective at destroying

non-enveloped viruses AND endospores.

Organisms that require gaseous oxygen for metabolism are referred to as

obligate aerobes.

Exergonic reactions

occur when there is more free energy in the reactants than the products.

Bacteria may be stored for several months

on a slant in the refrigerator, frozen in glycerol solution AND freeze-dried.

The name given to the reaction involving removal of electrons or hydrogen atoms from a compound is

oxidation.

Shake tubes are used to determine the

oxygen requirements for bacterial growth.

Bacteria that can absorb light energy and convert it into ATP are commonly called

phototrophs.

Silver sulfadiazine, which is a combination of silver and a sulfa drug, is used to

prevent infection of second- and third-degree burns.

Removing the electron transport chain of E. coli would

prevent oxidative phosphorylation.

Gamma rays cause biological damage in living systems by

producing reactive molecules such as superoxide.

Candle jars are used to

provide an atmosphere with increased CO2 levels.

All the bacterial cells that result from the replication of a single bacterial organism are referred to as a

pure culture.

Glycolysis, the Entner-Duodoroff pathway, and the pentose phosphate pathway all produce

pyruvate.

The name given to the reaction involving addition of electrons or hydrogen atoms to a compound is

reduction.

Generally, membrane filters are used for all of the following EXCEPT

removing enzymes from liquids.

The electron transport system

requires a membrane AND generates a concentration gradient of protons.

Generally the proteins of thermophiles

resist denaturation.

A medium that inhibits the growth of organisms other than the one being sought is called a(n)

selective medium.

Most enzymes function best at

slightly above pH 7 and low salt concentrations.

The process of killing or removing all of the microorganisms in or on a material is called

sterilization.

A common application of dry heat in the microbiology laboratory is to

sterilize the inoculating loop.

The simplest technique for isolating bacteria is referred to as the

streak-plate method.

Organisms may derive energy from

sunlight AND metabolizing chemical compounds.

The enzymes that deal with toxic oxygen-containing molecules are

superoxide dismutase AND catalase.

Environmental factors that may affect enzyme activity include

temperature, pH, AND salt.

Microwaves do not kill organisms directly but kill by

the heat they generate in a product.

Eosin methylene blue agar (EMB) is a selective and differential medium. The dyes in the medium inhibit most Gram-positive organisms. Gram-negative organisms such as the coliforms grow on this medium. Coliforms that are fecal in origin produce colonies with a metallic green color on EMB, while those that are non-fecal produce colorless colonies. You plate a urine sample onto an EMB plate and incubate it. Metallic green colonies develop. From this, you can conclude that

the sample contains bacteria that are Gram-negative AND are fecal in origin.

When filtering a liquid, it is a bad idea to use a membrane with a pore size smaller than necessary because

the smaller the pore size, the slower the filtration process, so you would be wasting time.

Compounds of tin, mercury, arsenic, and copper are no longer used to prevent microbial growth in cooling water primarily because

their use contributes to serious pollution of natural waters.

Each of the following statements about chemoorganotrophs is true EXCEPT

they may use photophosphorylation to produce ATP.

Degradation of fats as an energy source involves all of the following except

transamination.

Coenzymes are derivatives of

vitamins.