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Type of microbe associated with water pollution
Coliforms
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Properties of coliforms
- G--
- Rods
- Often found in intestines
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Examples of coloforms
E. coli, Salmonella, Shigella
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Hoe do coliforms enter water?
Usually through fecal matter
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How can selective media affect growth?
- Addition of inhibitors
- Change pH
- Omission of nutrients
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Differential media
- Contain specific growth indicators
- Demonstrate presence of substances
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EMB Agar
- Eosin methylene blue
- Selective for gram neg
- Lac Fermentors are blue
- Lac Non-fermentors are colourless
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Two indicators in EMB
- Eosin Y - Acidic
- Methylene blue - Basic
- The two dyes will react
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How do dyes generally work?
Acid production causes uptake of dye; changing colony colour
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MacConkey media
- Lactic acid fermentors (coliforms) turn red
- Bile salts and CV inhibit G++ growth
- Uses neutral red indicator
- Production of bial salts
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Property of gas detecting media?
Semi-solid
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Hugh and Leifson's method
- Uses semisolid peptone media
- Contains carbohydrate of interest
- pH Indicator - Bromothymol blue
- Stab inoculate
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Reactions to Hugh Leifson's method?
- Facultative; Acid, Entire media turns yellow from top down
- Using peptone only; Alkaline, blue colour only at top
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Motility media
- Triphenyl tetrazolium chloride (TTC)
- Semisolid, low [agar]
- TTC reduction by microbe causes red colour
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Reactions in motility media
- Facultative, motile; Whole tube becomes red
- Aerobic, motile; Only top of tube is red
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What does IMViC stand for
Indole, Methyl red, Voges Praskauer, Citrate
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Indole test
- Conversion of Trp to Indole (in peptone water)
- Kovak's reagent turns in pink in the presenc of indole
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Methyl red test
- Mixed acid fermentation
- Acid production lowers pH
- { if (pH < 5) colour = red;
- else colour = yellow }
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Voges-Praskaeur test
- Butenediol fermentation
- Non-acidic product
- Test for Acetyl methyl carbinol (intermediate)
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Citrate test
- Citrate is the only carbon source
- Oxidative formation of NaCO3 increases pH
- Grn->Blue
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Urea hydroysis
- Assay for urease activity
- Phenol red (violet->red) on pH increase (ammonia production)
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