6.2 Flashcards
Cardinal temperatures:
the range of temperatures for the growth of a given microbial species
: the lowest temperature that permits a microbe’s continued growth and metabolism; below this temperature, its activities are limited
Minimum temperature
the highest temperature at which growth and metabolism can proceed before proteins are denatured
Maximum temperature
an intermediate between the minimum and the maximum that promotes the fastest rate of growth and metabolism
Optimum temperature
6 different temperature organisms include
Psychrophiles:
Psychrotrophs:
Mesophiles:
Thermoduric:
Thermophile:
Extreme thermophiles:
Survive short exposure to high temperatures but are normally mesophiles
Common contaminants of heated or pasteurized foods
Examples are heat-resistant cysts such as Giardia and spore-formers such as Bacillus and Clostridium
Thermoduric
Optimum temperatures greater than 45°C
Live in soil and water associated with volcanic activity, compost piles, in habitats directly exposed to the sun
Vary in heat requirements with a range of growth of 45°C to 80°C
Alicyclobacillus
Thermophile
grow between 80°C and 121°C
Thermus aquaticus
Extreme thermophiles
Which atmospheric gases influence microbrial growth?
O2 and CO2
O2 has the greatest impact on microbial growth.
O2 is an important respiratory gas and a powerful oxidizing agent.
Microbes fall into one of three categories:
Those that use oxygen and detoxify it.
Those that can neither use oxygen nor detoxify it.
Those that do not use oxygen but can detoxify it.
What are the 2 highly reactive oxygens
Superoxide ion (O2-)
Hydroxyl radicals (OH-):
Which oxygen molecule is extremely reactive and why?
Singlet oxygen (O): an extremely reactive molecule that can damage and destroy a cell by the oxidation of membrane lipids
Which type of oxygen molecule is toxic to cells and used as a disinfectant
Hydrogen peroxide (H2O2):
Most cells have developed enzymes that scavenge and neutralize reactive oxygen byproducts.
Two-step process requires
2 enzymes
