Chapter 6 Flashcards

Terms Definitions
psychrophiles
cold-loving microbes
mesophiles
moderate-temperature-loving microbes
thermophiles
heat-loving microbes
minimum growth temperature
the lowest temperature at which the species will grow
optimum growth temperature
the temperature at which the species grows best
maximum growth temperature
the highest temperature at which growth is possible
psychotrophs
which food microbiologists favor, for this group of spoilage microorganisms
hyperthermophiles or extreme thermophiles
members of the archaea, have an optimum growth temperature of 80'C or higher
acidophiles
are remarkably tolerant of acidity
extreme halophiles
have adapted so well to high salt concentrations that they actually require them for growth
nitrogen fixation
use gaseous nitrogen directly from the atmosphere
obligate aerobes
organisms that require oxygen to live
facultative anaerobes
the ability to continue growing in the absence of oxygen
obligate anaerobes
are bacteria that are unable to use molecular oxygen for energy-yielding reactions
singlet oxygen
is normal molecular oxygen that has been boosted into higher-energy state and is extremely reactive.
superoxide radicals or superoxide anions
formed in small amounts during the normal respiration of organisms that use oxygen as a final electron acceptor, forming water.
hydroxyl radical
is another intermediate form of oxygen and probably the most reactive. It is formed in the cellular cytoplasm by ionizing radiation.
Aerotolerant anaerobes
cannot use oxygen for gorwth, but they tolerate it fairly well
microaerophiles
they are aerobic. they do require oxygen. they grow only in oxygen concentrations lower than those in air.
culture medium
a nutrient material prepared for the growth of microorganisms in a laboratory
inoculum
microbes that are introduced into a culture medium to initiate growth
culture
the microbes that grow and multiply in or on a culture medium
capnophiles
Microbes that grow better at high CO2 concentrations
Selective Media
are designed to suppress the growth of unwanted bacteria and encourage the growth of the desired microbes
Differential Media
make it easier to distinguish colonies of the desired organism from other colonies growing on the same plate.
streak plate method
The isolation method most commonly used to get pure cultures
Deep-freezing
is a process in which a pure culture of micobes is placed in a suspending liquid and quick-frozen at temperatures ranging from -50'C to -95'C
Lyophilization(freeze-drying)
a suspension of microbes is quickly frozen at temperatures ranging from -54'C to -72'C and the water is removed by a high vacuum.
Generation time
The time required for a cell to divide (and it's population to double).
Death Phase
The number of deaths eventually exceeds the number of new cells formed
Plate count
The most frequently used method of measuring bacterial populations
Turbidity
is a practical way of monitoring bacterial growth
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