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Starch (amylase) hydrolysis test
- Tests if the bacteria has a exoenzyme (a enzyme that leaves the cell to break down big molecules like starch) amylase.
- Once the bacteria has grown but grams iodine
- positive reaction there will be a clearing around the growth (because it ate the starch)
- Negative is no clearing around it once you add the iodine.
- Casein is what makes milk opaque
- This test tests for bacteria that release a exoenzyme caseinase (breaks down the casein in the culture)
- A postive reaction will have clearing around the bacterial growth (because it will break down the casein in the milk agar)
- Negative willl have no clearing around the bacterial growth.
Indole Test (tryptophan test)
- This tests to see if the bacteria create tryptophanase that is able to break down tryptophan.
- Once the broth has grown add 10 drops of kovac's reagant. The bacteria that does this uses pyruvate and ammonia as food.
- If it's positive there will be a cherry red ring at the top of the tube
- Negative reaction will have a green or yellow ring
- Some enteric bacteria have a enzyme called urease that breaks down urea into CO2 and ammonia.
- Phenol red is also used in it as a pH indicator red to yellow is a acidic 6.8pH or lower bright pink is 8.1pH or higher
- A positive result is bright pink a negative result is yellow or beige (beige meaning medium)
Catalase production test
- aerobic, facultative anaerobic and aerotolerant bacteria have protective enzymwa that reduce O2 toxicity by converting these derivatives to less harmful products
- this test tests for the presense of catalase
- Positive is if bubbles are produced
- negative is if no bubbles are produced
- This tests for the abiltiy for bacteria to produce cytochrome oxidase
- Positive if it turns blue
- Negative if it doesn't turn a color