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45 terms

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
pH.
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?
turbidity
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)
chemostat.
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
mesophiles.
MacConkey agar plates represent __________ medium.
both a differential and a selective
__________ are complex communities of various types of microbes that adhere to surfaces.
Biofilms
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
photoheterotroph.
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?
heme.
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
protease.
A specimen of urine is determined to contain 30 bacterial cells per microliter. How many cells would be present in a milliliter?
30,000