Physiological Tests (Parts 1-3)

carbohydrate fermentation tests

1. carbohydrate source (glucose, lactose, mannitol) = carbon source → energy source for bact.

2. phenol red = pH indicator

   1. positive for carbohydrate fermentation → acid production (enz) → pH ↓ + gas → color changes (red to yellow)

   2. negative: red/peach orange

   3. degraded peptone (protein present in broth) → alkaline by-product ↑ pH → will NOT turn yellow / turns BRIGHT PINK

carbohydrate fermentation tests (results)

• A = positive acid

• G = positive gas

• K = peptone

• - = negative

IMViC tests

group of 4 biochemical reaction tests used to determine the Genus name of facultative anaerobe, gram-negative bacilli

• I = indole production test

• M = methyl red test

• V = Voges-Proskauer test (skip)

• C = citrate utilization test

carbohydrate fermentation tests

see if bacteria utilize a specific carbohydrate as an energy source by breaking it down with enzyme

• medium: glucose PRB, lactose PRB, mannitol PRB

• test/pH indicator: Phenol Red (pH indicator)

• negative: - acid (red → red/peach-orange); - gas (no bubbles)

• positive: + acid (red → yellow); + gas (bubbles)

  • peptone: alkaline protein byproduct ↑ pH → BRIGHT PINK

gelatinase test

see if bact. breaks down gelatin by making gelatinase

• medium: nutrient gelatin deep

• test or pH indicator: gelatin (test indicator)

• negative: solid → solid (no liquefaction)

• positive: solid → liquefaction

amylase/starch hydrolysis test

test if bact. can breakdown amylose/starch (polysaccharide) by producing enzyme amylase

• medium: starch agar plate

• test indicator:

urease test