Micro Exam 2 2
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- Name the physical control methods with heat
- direct flame, hot-air oven, boiling water, autoclave, pasteurization, and High temperature-short time (flash pasteurization)
- what what physical control method removes microorganisms larger than the pore size of the filter? and what is the size needed to remove virus's?
- filtration, typical pore size is .2-.45 um, .1 um required to remove viruses
- How does UV light work?
- Adjacent pyrimidines link together forming dimmers, often used to control microbes in air, favorite method for sterilization of large surface areas
- Differeniate between thermal death time and thermal death point
- thermal death time-time necessary to kill a microorganism at a given temperature, thermal death point-lowest temperature required to kill a liquid culture of a certain species in 10' at pH 7.00
- Differentiate between ionizing radiation and ultraviolet radiation and their effects on microbial cells
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Ultraviolet Light (none ionizing irradiation)
a. adjacent pyrimidines link together forming dimmers
Ionizing radiation: use cobalt 60 cause damage by forming free radicals which attack DNA - What organism is the "world's toughest" bacterium?
- Deinococcus radiodurans
- What two bacterial species are contained on a test strip in order to test if sterilization has been sucessful?
- Bacillus stearothermophilis and Bacillus subtilis
- Are gram + or gram - bacteria more sensitive to radiation?
- Gram positive
- What effect of moist heat on microorganisms is destrcution of proteins by the process of?
- oxidizes proteins and dehydrates cells
- Pasteurization, known as "low temperature, long time" is done how?
- 62.9C for 30'
- Flash pasteurization, HTST done how?
- 140C for 3s
- Describe the autoclaves operating conditions
- 15 psi, 121.5C, 15'
- HEPA filters remove how many particles?
- 99%
- Describe the methods availible for long-term storage of bacterial cultures
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Deep freezing-40% glycerol used, stored in -70C
Lyophilization-stored -70C and water removed through use of vacuum - What are the 3 categories of hemolytic activity observed by bacteria on blood agar plates? Differeniate.
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Beta-bacteria completely lyse RBSs, results in clearing of colony
Alpha-incomplete hemolysis causes geening area around colony
Gama-absence of hemolysis - What are the 3 genera of bacteria collectivelly called rhizobia?
- Rhizobium, Bradyrhizobium, Azorhizobium
- What is ment by the Rhizosphere effect?
- bacteria chemotically attracted to roots due to secreation of flavoniod compounds
- How are cyanobacteria important to the agriculture of asia?
- Anabaena azollaw important to rice farming
- Why are lichens considered biosensors?
- sensitive to air quality
- How do symbiotic plant-microbe relationships of Azosprillium differ from those of Frankia and the rhizobia?
- Azospirollium lives between root cells (intercellular) and dont induce root nodules
- What is the different between defined media and complex media?
-
Complex-cannot be sure of components or quanity
Defined-ingrediants and amounts known - Describe the symbiotic relaitonship of mycorrhiza
- Fungi and roots of vascular plant
- Describe the symbiotic relationship that forms lichens
- fungi and algae or cyanobacteria
- Differentiate between the following:mutualism, commensalism and parasitism
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mutualism-positive for both
commensalism-one organism benefits doesnt help/harm other
parasite-one organism benefits at expense of host - How does the relationship between the giant amoeba Pelomyxa palustris and one of the bacterial endosymbionts provide evidence for the endosymbiotic theory of cellular evolution?
- internal structures resemble cristea of mitochondria
- Describe essential symbiotic relationship between ruminants and microorganisms
- microorganisms help to digest materials and microbes get food
- mechanism for henol/phenolic compounds
- denatures proteins, especially in cell wall
- Cresols (mentholated phenol)
- denatures proteins, it has the ability to reduce surface tension by loosening bacteria from tissue allowing greater penetration of antiseptic
- Alcohols
- denatures proteins and dissolves lipids, cell membrane disintegration, strong dehydration agents
- Soaps
- emulsify oily layer of the skin along with mucrobes is broken up and vanishes down with water being rinsed
- Cationic detergents
-
derivatives ammonium chloride containing four organic groups in place of the four hydrogens at leadt one group long alkyl group
Negatively charged lipid membrane of bacterial cell attracts positively charged bacterial components of cationic detergent molecule - Chlorine
- free chlorine added directly to water a reaction occurs form hypocholorous acid
- Alkylating agents
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attach methyl or ethyl group to proteins and DNA, rendering molecules nonfunctional and causing death of microorganisms
Reacts with amino and hydroxyl groups of nucleic acids and proteins and carboxyl and stulfhydryl groups in proteins inserting an alkyl between them - Heavy metals
- Brings to sufhydryl groups of proteins and denature them
- Acids
- mechanism of action and damage microbial membranes and interfere with the uptake of certain essential organic substances like amino acids