Lab practical Flashcards
Acetoin/Vogues Test
Grow in peptone broth. Tests if the microbe undergoes the butanediol fermentation pathway of glucose. Red is positive, no color change is negative.
Indole Test
Grow in tryptone broth. Tests for the presence of tryptophanase (for catabolizing tryptophan). Pink/red on top = +, yellow-brown = negative.
Ornithine Test
Grow in glucose/ornithine broth with pH indicator. Tests for the presence of ornithine decarboxylase (used in the first step of ornithine catabolism). Positive results are purple, yellow is negative)
Catalase test
Tests for the presence of catalase (gets rid of toxic oxygen species). Positive results form bubbles.
Casein hydrolysis Test
Does it produse caseinase (enzyme to hydrolyze casein). Grow on milk plate -> positive show clearing, negative shoes no appearance change in agar.
Citrate Test
Can it use citric acid/citrate as sole C source. Simmon’s citrate slant -> growth is a positive result, with or without color change.
Fermentation Tests (Durham vial)
Is there gas in the vial and did it produce acid (pink yes it did, yellow no it didn’t)
Gelatine Hydrolysis Test
Can it hydrolyze gelatine (using gelatinases)? Gelatin/nut tube. If it’s liquid it’s positive, negative are solid (let it sit in cold for a bit first before observing).
Methyl Red Test
Tests for mixed acid fermentation pathway (is a lot of acid produced in glucose fermentation). Red is positive, yellow negative, and orange inconclusive.
Motility Deeps
Straight needle in, does it grow just along stab or does it move out into the agar (pink diffusion or solid line). More motility when at temp lower than optimal growth.
Nitrate reduction test
Can it reduce nitrogen? Could be fully or just partway. If color change at first it’s positive (NO3 to No2), if you add zinc and still no change it’s also positive (went from NO3 to NO2 to N2). Zinc forces any NO3 to become NO2 so if there is none then no change
Oxidase Test
Testing for cytochrome c oxidase. (terminal e- acceptor in some aerobic respirers). Pink is positive, no change is negative
Urease Test
Can it hydrolyze Urea to use as nitrogen. Grow on urease agar slant and look for pink (+) or yellow (-).
Start hydrolysis test
Does it produce amylase? Grow on starch plate, cover in iodine, look for clearing/transparent agar around colonies (+).
How can you differentiate Acinetobacter and Pseudomonads? And why are they hard to tell apart?
Pseudomonas are motile, oxidase +, G - rods, obligate respirers
Acinetobacter are non-motile and Oxidase -, G - cocci-bacilli, obligate aerobe,
Both utilize weird carbons, are found in a similar location (soil/water), and prefer growing in oxygen.
