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35 terms

Chapter 6: Microbial Nutrition

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What is the maximum growth temperature for a mesophile?
40 degree C
A colony-forming unit is a _____.
single cell or group of related cells that gives rise to a colony
What technique is most useful for measuring microbial reproduction when the density of a microbial population is very small?
membrane filtration
What does NOT use an inorganic source of carbon as its sole source?
photoheterotroph
Media containing sodium thioglycollate are used for the growth of?
obligate anaerobes
Microbial growth is at its maximum rate during which phase of the microbial growth curve?
log phase
What does NOT happen at the maximum growth temperature of a microorganism?
membranes become rigid and fragile
Why would a particular microbe need to be cultured inside an animal?
Standard laboratory culture techniques have proven inadequate.
Crenation can result from a change in what?
osmotic pressure
A chemoheterotroph obtains its energy from _____ and its carbon from _____ sources.
redox reactions; organic
The most commonly used isolation technique in microbiology laboratories is the _____.
streak-plate method
A spectrophotometer is useful for what method of measuring microbial growth?
turbidity
Nitrogen is a growth-limiting nutrient because cells need it to manufacture _____.
proteins and nucleotides
Blood agar is an example of _____.
differential medium and complex medium
Microbes in the _____ phase of the microbial growth curve are most susceptible to antimicrobial drugs.
log
Fermented foods such as sauerkraut or pickles are kept from spoiling by the effects of?
pH
A(n) _____ organism is one that requires oxygen for growth.
obligate aerobic
Human pathogens are classified as _____.
mesophiles
Organisms that can grow with or without oxygen present are
facultative anaerobes or aerotolerant anaerobes
The use of salt and sugar in preserving various types of foods is an application of what concept?
osmotic pressure
An organism that tolerates high _____ is called a halophile.
salt concentrations
Microaerophiles are microbes which grow best at low ______.
oxygen levels
An acidophile thrives under conditions of low _____.
pH
T/F Nitrogen fixation is a process that occurs in all bacteria.
False
T/F Obligate anaerobes have enzymes such as superoxide dismutase to protect them from the damaging effects of oxygen.
False
What quantification technique can distinguish living cells from dead cells in a culture?
metabolic activity
New cells are being produced at the same rate as other cells are dying during the _____ of growth.
stationary phase
Bacterial growth is defined as
increase in bacterial cell population
In which phase is the rate of cell death equal to the rate of cell growth?
stationary phase
Why is cell growth typically graphed logarithmically?
Cell growth is rapid, and plotting the log of the number of cells versus the generation on a logarithmic graph produces a linear graph.
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
What enables the copied chromosomes to separate during binary fission?
The chromosomes are attached to different parts of the cell membrane, which elongates and thus separates the chromosomes.
How long does it take for the daughter cells from one round of replication to replicate themselves?
No time is required- they are fully mature and ready to divide immediately after separation if conditions are right.
What would happen if the septum did not form during binary fission?
The parent cell would now have two copies of the chromosome.
Which step of binary fission is the reason for genetically identical daughter cells?
Replication of the bacterial chromosome