mastery quiz 6

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A colony-forming unit is the number of cells

that produces one colony.

An acidophile thrives under conditions of low


In microbiology, the term growth usually refers to an increase in

the number of microbial cells.

A(n) __________ organism is one that requires oxygen for growth.

obligate aerobic

Another term for the logarithmic growth of bacterial cells is

exponential growth.

Cells are rapidly growing and dividing during the __________ of growth.

log phase

At temperatures higher than the maximum growth temperature for an organism,

hydrogen bonds are broken, proteins are denatured, and membranes become too fluid.

During which growth phase are bacteria more susceptible to antimicrobial drugs?

log phase

Which of the following is NOT a direct method for measuring the number of microbes in a sample?


During the __________ of growth, cells are dying faster than new cells are being produced.

death phase

The use of salt and sugar in preserving various types of foods is an application of which of the following concepts?

osmotic pressure

The term barophile refers to which of the following growth requirements?

hydrostatic pressure

A device that removes wastes and adds fresh medium to bacterial cultures in order to prolong the log phase of a culture is called a(n)


A Petroff-Hauser counting chamber is

a glass slide containing an etched grid for counting microbes directly using a microscope.

A capnophile is a microorganism that thrives in conditions of high __________.

carbon dioxide levels

Microaerophiles are microbes that grow best at low

oxygen levels.

When cells are metabolically active but not dividing, they are in the

lag phase.

An organism that tolerates high __________ is called a halophile.

salt concentrations

Sodium thioglycollate is associated with which of the following types of media?

reducing media

Which of the following organisms would be most likely to contaminate a jar of pickles?

an acidophile

All of the following ingredients might be found in complex media EXCEPT

hydrogen peroxide.

Obligate anaerobes may be cultured in the laboratory

in a reducing medium.

A clinical sample labeled as "sputum" was collected from

the lungs.

Which of the following forms of oxygen is detoxified by the enzyme catalase?

peroxide anion

Human pathogens are classified as


MacConkey agar plates represent __________ medium.

both a differential and a selective

__________ are complex communities of various types of microbes that adhere to surfaces.


An aquatic microbe that can grow only at the surface of the water is probably which of the following?

a phototroph

A microbe that grows only at the bottom of a tube of thioglycollate medium is probably a(n)

obligate anaerobe.

Nitrogen is a growth limiting nutrient for many organisms because

only a few microbes can extract it from the atmosphere, but all organisms require it for amino acid and nucleotide synthesis.

during the __________ of growth, new cells are being produced at the same rate as other cells are dying.

stationary phase

A fastidious organism might be grown on which of the following types of media?

enriched media

A cell that uses an organic carbon source and obtains energy from light would be called a


A microbiologist inoculates a growth medium with 100 bacterial cells/ml. If the generation time of the species is 1 hour, and there is no lag phase, how long will it be before the culture contains more than 10,000 cells/ml?

7 hours

Which of the following quantification techniques can distinguish living cells from dead cells in a culture?

metabolic activity

during the __________ of growth, new cells are being produced at the same rate as other cells are dying.

stationary phase

Organisms that can grow with or without oxygen present are

either facultative anaerobes or aerotolerant anaerobes.

Microaerophiles are microbes that grow best at low

oxygen levels.

An epidemiologist is investigating a new disease and observes what appear to be bacteria inside tissue cells in clinical samples from victims. The scientist wants to try to isolate the bacteria in the lab. What culture conditions are most likely to be successful?

inoculation of cell cultures

Which of the following growth factors would NOT be required by microbes which do not utilize electron transport chains?


Joan wants to discover a microbe capable of degrading an environmental contaminant. Which of the following refers to the process she should use?

enrichment culture

The method of obtaining isolated cultures that utilizes surface area to dilute specimens is called

the streak-plate technique.

Which of the following measurement techniques would be useful to quantify a species of bacteria that is difficult to culture?

microscopic counts

All of the following are used to protect organisms from the toxic by-products of oxygen EXCEPT


A specimen of urine is determined to contain 30 bacterial cells per microliter. How many cells would be present in a milliliter?


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