BIOS 390 quiz 3 - –Answer -to identify appropriate culture meth...

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BIOS 390 quiz 3

• Why are cultural methods important/useful?

–Answer -to identify appropriate culture methods needed to evaluate microbial diversity -determine which specific microbes/group of microbes are present -the type of environmental sample (soil, aquatic/marine) -anaerobic or autotrophic bacteria -dilution/concentration -selective or differential growth media

• What are the steps needed to extract cells from soil?

–Answer mechanical shaking (with or w/o beads) -> serial dilution -> plating methods (spead or pour) -> incubation

• what are the steps needed to extract cells from water (low numbers of bacterial cells)?

–Answer concentration filtered though a membrane -> plating methods (spread or pour) -> incubation

• Plate counts determine

–Answer colony forming units (CFUs)

• Why is serial dilution used?

–Answer to ensure the right number of colonies of the original inoculum

• serial dilution method

–Answer to determine the number of bacteria in a given sample, the number of bacteria in a given sample is usually too great to count

• CFU equation

–Answer CFU= (total colonies / dilution amount) 1 / 2

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• culture medium

–Answer A nutrient material prepared for the growth of microorganisms in a laboratory

• sterile

–Answer no living microbes

• Inoculum

–Answer introduction of microbes into medium

• culture

–Answer microbes growing in/on culture medium

• Agar

–Answer Complex polysaccharide Used as solidifying agent for culture media in Petri plates, slants, and deeps Generally not metabolized by microbes Liquefies at

100°C

Solidifies at

~40°C

• chemically defined media

–Answer exact chemical composition is known

• fastidious organisms

–Answer require many growth factors provided in chemically de- fined media

• complex media

–Answer extracts and digests of yeasts, meat, or plants (includes blood, serum)

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