Acetic succinic lactic and formic acids also very stable end products Methyl

Acetic succinic lactic and formic acids also very

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Acetic, succinic, lactic, and formic acids – also very stable end products Methyl red is a pH indicator which detects only very strong acids (pH 4.4 and below) MR/VP Test Both the Voges Proskaeur and Methyl Red tests are conducted using MR/VP broth, which contain glucose. Fermentation is detected with various reagents VP - α-naphthol and 40% KOH – pink/rose color indicates the presence of acetoin MR – methyl red pH indicator – is normally red and will lose color in pH higher than 4.4 – positive will remain red; strong acids present
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Bile Esculin Used to differentiate gamma-hemolytic Streptococcus from Enterococcus . Bile salts are the selective ingredient, while esculin is the differential ingredient Enterococcus (Group D streptococci) hydrolyze esculin Breakdown products react with ferric citrate in the medium to produce insoluble iron salts As a result, the media changes color to black. Carbohydrate Fermentation (a.k.a. Acid & Gas Production) Different m/o utilize carbohydrates differently Depends on enzymes available Some use respiration (aerobic or anaerobic) Some use fermentation Carbohydrate Fermentation metabolic process in which organic molecules (carbs) act as e - donors and one or more of its organic products act as the final e - acceptor = ENERGY Different fermentation pathways are named for their end products Gas is sometimes given off (usually CO 2 ) Carbohydrate Fermentation The test 2 tubes (phenol red broth) Specific carb (glucose, mannitol) pH indicator phenol red pH < 6.8 = yellow = acid production = fermentation pH > 7.4 = pink Peptone (growth enhancer containing a.a.) Durham tube Bubble = Gas No Bubble = No Gas Measures ability of bacteria to ferment a specific carbohydrate and produce gas Yellow = + fermentation Bubble = + gas production Lack of fermentation does NOT indicate absence of growth Some m/o use other nutrients (peptides) as energy sources peptides a.a. keto – a.a. ammonia alkaline pH Alkaline pH = pink
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