exam 3 review BIOL 2460

Which of the following methods would be used to measure the concentration of bacterial contamination in processed peanut butter?

total plate count

In which phase would you expect to observe the most endospores in a Bacillus cell culture?

death phase

During which phase would penicillin, an antibiotic that inhibits cell-wall synthesis, be most effective?

log phase

Which of the following is the best definition of generation time in a bacterium?

the length of time it takes for a population of cells to double

What is the function of the Z ring in binary fission?

It forms a contractile ring at the septum.

If a culture starts with 50 cells, how many cells will be present after five generations with no cell death?

1600

Filamentous cyanobacteria often divide by which of the following?

fragmentation

Which is a reason for antimicrobial resistance being higher in a biofilm than in free-floating bacterial cells?

Cells are metabolically inactive at the base of a biofilm.

Quorum sensing is used by bacterial cells to determine which of the following?

the density of the population

Which of the following statements about autoinducers is incorrect?

They bind directly to DNA to activate transcription.

An inoculated thioglycolate medium culture tube shows dense growth at the surface and turbidity throughout the rest of the tube. What is your conclusion?

The organisms are facultative anaerobes.

An inoculated thioglycolate medium culture tube is clear throughout the tube except for dense growth at the bottom of the tube. What is your conclusion?

The organisms are obligate anaerobes.

Pseudomonas aeruginosa is a common pathogen that infects the airways of patients with cystic fibrosis. It does not grow in the absence of oxygen. The bacterium is probably which of the following?

an obligate aerobe

Streptococcus mutans is a major cause of cavities. It resides in the gum pockets, does not have catalase activity, and can be grown outside of an anaerobic chamber. The bacterium is probably which of the following?

an aerotolerant anaerobe

Why do the instructions for the growth of Neisseria gonorrhoeae recommend a CO₂-enriched atmosphere?

It is a capnophile.

Bacteria that grow in mine drainage at pH 1–2 are probably which of the following?

acidophiles

Bacteria isolated from Lake Natron, where the water pH is close to 10, are which of the following?

alkaliphiles

In which environment are you most likely to encounter an acidophile?

a hot vent at pH 1.5

A soup container was forgotten in the refrigerator and shows contamination. The contaminants are probably which of the following?

psychrotrophs

Bacteria isolated from a hot tub at 39 °C are probably which of the following?

mesophiles

In which environment are you most likely to encounter a hyperthermophile?

hydrothermal vent at the bottom of the ocean

Which of the following environments would harbor psychrophiles?

mountain lake with a water temperature of 12 °C

Which of the following is the reason jams and dried meats often do not require refrigeration to prevent spoilage?

low water activity

Bacteria living in salt marshes are most likely which of the following?

halotolerant

EMB agar is a medium used in the identification and isolation of pathogenic bacteria. It contains digested meat proteins as a source of organic nutrients. Two indicator dyes, eosin and methylene blue, inhibit the growth of gram-positive bacteria and distinguish between lactose fermenting and nonlactose fermenting organisms. Lactose fermenters form metallic green or deep purple colonies, whereas the nonlactose fermenters form completely colorless colonies. EMB agar is an example of which of the following?

a selective medium, a differential medium, and a complex medium

Haemophilus influenzae must be grown on chocolate agar, which is blood agar treated with heat to release growth factors in the medium. H. influenzae is described as ________.

fastidious

___Number of dying cells is higher than the number of cells dividing

Death phase

___Number of new cells equal to number of dying cells

Stationary phase

___New enzymes to use available nutrients are induced

Lag phase

___Binary fission is occurring at maximum rate

Log phase

___psychotroph

food spoiling in refrigerator

___mesophile

human pathogen

___thermophile

garden compost

___hyperthermophile

hydrothermal vent

___psychrophile

deep ocean waters

Direct count of total cells can be performed using a ________ or a ________.

hemocytometer, Petroff-Hausser counting chamber

The ________ method allows direct count of total cells growing on solid medium.

plate count

A statistical estimate of the number of live cells in a liquid is usually done by ________.

most probable number

For this indirect method of estimating the growth of a culture, you measure ________ using a spectrophotometer.

turbidity

Active growth of a culture may be estimated indirectly by measuring the following products of cell metabolism: ________ or ________.

ATP, acid from fermentation

A bacterium that thrives in a soda lake where the average pH is 10.5 can be classified as a(n) ________.

alkaliphile

Lactobacillus acidophilus grows best at pH 4.5. It is considered a(n) ________.

acidophile

A bacterium that thrives in the Great Salt Lake but not in fresh water is probably a ________.

halophile

Bacteria isolated from the bottom of the ocean need high atmospheric pressures to survive. They are ________.

barophiles

Staphylococcus aureus can be grown on multipurpose growth medium or on mannitol salt agar that contains 7.5% NaCl. The bacterium is ________.

halotolerant

Blood agar contains many unspecified nutrients, supports the growth of a large number of bacteria, and allows differentiation of bacteria according to hemolysis (breakdown of blood). The medium is ________ and ________.

complex, differential

Rogosa agar contains yeast extract. The pH is adjusted to 5.2 and discourages the growth of many microorganisms; however, all the colonies look similar. The medium is ________ and ________.

complex, selective

Which of the following types of medical items requires sterilization?

needles

Which of the following types of medical items requires sterilization?

needles

Which of the following is suitable for use on tissues for microbial control to prevent infection?

antiseptic

Which biosafety level is appropriate for research with microbes or infectious agents that pose moderate risk to laboratory workers and the community, and are typically indigenous?

BSL-2

Which of the following best describes a microbial control protocol that inhibits the growth of molds and yeast?

fungistatic

The decimal reduction time refers to the amount of time it takes to which of the following?

reduce a microbial population by 90%

Which of the following methods brings about cell lysis due to cavitation induced by rapid localized pressure changes?

sonication

Which of the following terms is used to describe the time required to kill all of the microbes within a sample at a given temperature?

thermal death time

Which of the following microbial control methods does not actually kill microbes or inhibit their growth but instead removes them physically from samples?

filtration

Which of the following refers to a disinfecting chemical dissolved in alcohol?

tincture

Which of the following peroxygens is widely used as a household disinfectant, is inexpensive, and breaks down into water and oxygen gas?

hydrogen peroxide

Which of the following chemical food preservatives is used in the wine industry but may cause asthmatic reactions in some individuals?

sulfites

Bleach is an example of which group of chemicals used for disinfection?

halogens

Which chemical disinfectant works by methylating enzymes and nucleic acids and is known for being toxic and carcinogenic?

formaldehyde

Which type of test is used to determine whether disinfectant solutions actively used in a clinical setting are being used correctly?

in-use test

The effectiveness of chemical disinfectants has historically been compared to that of which of the following?

phenol

Which of the following refers to a germicide that can kill vegetative cells and certain enveloped viruses but not endospores?

low-level germicide

Sanitization leaves an object free of microbes.

false

Ionizing radiation can penetrate surfaces, but nonionizing radiation cannot.

True

Moist-heat sterilization protocols require the use of higher temperatures for longer periods of time than do dry-heat sterilization protocols do.

False

Soaps are classified as disinfectants.

False

Mercury-based compounds have fallen out of favor for use as preservatives and antiseptics.

True

A medical item that comes into contact with intact skin and does not penetrate sterile tissues or come into contact with mucous membranes is called a(n) ________ item.

noncritical

The goal of ________ ________ protocols is to rid canned produce of Clostridium botulinum endospores.

commercial sterilization

In an autoclave, the application of pressure to ________ is increased to allow the steam to achieve temperatures above the boiling point of water.

steam

Doorknobs and other surfaces in clinical settings are often coated with ________, ________, or ________ to prevent the transmission of microbes.

copper, nickel, zinc

If a chemical disinfectant is more effective than phenol, then its phenol coefficient would be ________ than 1.0.

greater

If used for extended periods of time, ________ germicides may lead to sterility.

high-level

In the disk-diffusion assay, a large zone of inhibition around a disk to which a chemical disinfectant has been applied indicates ________ of the test microbe to the chemical disinfectant.

susceptibility or sensitivity

A scientist discovers that a soil bacterium he has been studying produces an antimicrobial that kills gram-negative bacteria. She isolates and purifies the antimicrobial compound, then chemically converts a chemical side chain to a hydroxyl group. When she tests the antimicrobial properties of this new version, she finds that this antimicrobial drug can now also kill gram-positive bacteria. The new antimicrobial drug with broad-spectrum activity is considered to be which of the following?

semisynthetic

Which of the following antimicrobial drugs is synthetic?

sulfanilamide

Which of the following combinations would most likely contribute to the development of a superinfection?

long-term use of broad-spectrum antimicrobials

Which of the following routes of administration would be appropriate and convenient for home administration of an antimicrobial to treat a systemic infection?

oral

Which clinical situation would be appropriate for treatment with a narrow-spectrum antimicrobial drug?

treatment of strep throat caused by culture identified Streptococcus pyogenes

Which of the following terms refers to the ability of an antimicrobial drug to harm the target microbe without harming the host?

selective toxicity

Which of the following is not a type of β-lactam antimicrobial?

glycopeptides

Which of the following does not bind to the 50S ribosomal subunit?

tetracyclines

Which of the following antimicrobials inhibits the activity of DNA gyrase?

nalidixic acid

Which of the following is not an appropriate target for antifungal drugs?

cholesterol

Which of the following drug classes specifically inhibits neuronal transmission in helminths?

avermectins

Which of the following is a nucleoside analog commonly used as a reverse transcriptase inhibitor in the treatment of HIV?

azidothymidine

Which of the following is an antimalarial drug that is thought to increase ROS levels in target cells?

artemisinin

Which of the following resistance mechanisms describes the function of β-lactamase?

drug inactivation

Which of the following resistance mechanisms is commonly effective against a wide range of antimicrobials in multiple classes?

efflux pump

Which of the following resistance mechanisms is the most nonspecific to a particular class of antimicrobials?

efflux pump

Which of the following types of drug-resistant bacteria do not typically persist in individuals as a member of their intestinal microbiota?

MRSA

In the Kirby-Bauer disk diffusion test, the _______ of the zone of inhibition is measured and used for interpretation.

diameter

Which of the following techniques cannot be used to determine the minimum inhibitory concentration of an antimicrobial drug against a particular microbe?

Kirby-Bauer disk diffusion test

The utility of an antibiogram is that it shows antimicrobial susceptibility trends

in a localized population.

Which of the following has yielded compounds with the most antimicrobial activity?

soil

Narrow-spectrum antimicrobials are commonly used for prophylaxis following surgery.

False