BIOL241 Study Guide - Quiz Guide: Exotoxin, Numerical Taxonomy, Bioavailability
21 Sep 2016
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Biol 241 lab review: direct microscopic count of microorganisms in milk. Disadvantages: not accurate on low-count milk, dead cells can be counted, tiring to use microscope, can be difficult to see. Microscope factor: relationship of the field to a ml. Results: raw = 49 million, fresh pasteurized = 32 million, past-date = 72 million. Spread or pour plate method with serial dilutions. Disadvantages: only organisms that can utilize the provided nutrients/conditions grow, arise from single cells or clumps. Results: unpasteurized = 106, pasteurized = 100-1000 cfu/ml: microbiological analysis of cheese. Streptococcus, lactobacillus: form lactic acid, start cheese-making process: causes acidification, souring, cheese flavours. Clostridium or coliform (ec, ea) bacteria: form gas defect in cheese. 100 million colonies/g: e. coli: green, metallic, enterobacter aerogenes: pink fish eye colonies. Malt extract: 4. 5 ph, selects for fungi. 250 000: penicillium will be white or green. Food poisoning: caused by enterotoxins (exo or endo) Enrichment step: needed for salmonella (present in small #s)
