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Lab #10 Physical Control of Microbial Growth

Terms in this set (18)

By sampling and inoculating organisms after exposure to boiling we are testing for
Whether or not the organism could survive boiling conditions
Ultraviolet light is a form of:
Nonionizing radiation
What do some species create that allow them to tolerate ultraviolet light?
Endospores
Boiling is an example of ________ heat that can efficiently destroy bacterial vegetative cells.
Moist
Why do communities issue water boil alerts?
to kill vegetative forms of microbes in the water and render it safe for drinking
What are the limitations to using UV for sterilization?
UV light has a lower energy and can't penetrate thus it is limited to surface use. In addition, it doesn't reliably kill endospores.
Did vegetative cells of an endospore former have any additional resistance to boiling than a non-‭endospore former? Why or why not?‭
Yes because of their ability to form heat resistant endospores which allows for their survival as an organism.
One of the cultures of B. subtilis used for both boiling and UV experiments was a week old. Why ‭was it important to continue the growth past the typical 48hrs?
Since they can't form endospores within a few minutes, it is neccessary to force the bacteria to form endospores ahead of time by creating nutrient depletion through extended incubation time.
The directions on a package of infant pacifiers says to sterilize by boiling before using, is this ‭possible?
No because boiling will only reach 100C which is not hot enough to kill endospores so it won't be sterile. However I don't expect to have soil contamination on pacifiers directly from the package. So boiling is sufficient to kill any vegetative cells that could cause disease and might be present.
In which case(s) would boiling water for drinking purposes not be sufficient?
presence of protozoa cysts or endospores, neither of which are reliably killed by boiling
disinfect
destroy most disease causing microbes
sterilize
remove all life forms and viruses
X-rays and gamma rays
Ionizing radiation
UV radiation
causes covalent bonds to form between adjacent pyrimidine bases. Replication is terminated.
In the presence of visible light
Enzyme DNA photolyase is activated, light repair "photoreactivation" occurs. DNA replication can then proceed normally.
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