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Bio Lab 4
| Question | Answer |
|---|---|
| Catalase Test | Catalase is an enzyme produced by bacteria to detoxify hydrogen peroxide (H2O2) to H2O and O2 gas |
| True or False: Red blood cells have catalase activity | True; Therefore, performing the catalase test with cells growing on blood agar will show you a false positive result. |
| Catalase Producers | Staphylococcus species (Gram +) |
| Catalase non-producers | Streptococcus species (Gram +) |
| Starch hydrolysis test | Starch is a polymer composed of glucose units joined by glycosidic bonds |
| Organisms that can utilize starch produce EXTRACELLULAR enzymes such as | amylase and glucosidase |
| positive starch test | clear |
| negative starch test | blue-black |
| Citrate utilization test | tests the ability of organisms to utilize citrate as a carbon source |
| Enzyme that breaks down sodium citrate to produce ammonium compounds and lowers pH | citrate permease |
| Citrus Slant Test positive | Green to Blue |
| Citrus Slant Test Negative | Green |
| Motility test | Differentiate between motile and non-motile bacteria |
| How is medium different in Motility test? | The medium has reduced agar concentration, from 1.5% (normal) to 0.4% (motility) to allow motile bacteria to swim through the media |
| Positive Motility test | red radiating outward from stab line |
| Negative Motility test | Red color only on stab line |
| Triple sugar iron agar (TSIA) | Differentiate based on organism ability to reduce sulfur and ferment carbohydrates |
| Three Sugars in Triple sugar iron agar (TSIA) | lactose, sucrose, glucose |
| Positives in Triple sugar iron agar (TSIA) | •Positive for carbohydrate - yellow color change •Positive for sulfur - Black color •Positive for gas production - air bubble, cracking, lifting of slant |
| Carbohydrate fermentation | Test for the utilization of different source of carbon. Carbohydrates fermentation is detected with phenol red broth |
| Carbohydrate fermentation yellow | Positive test. pH less than 6.8 |
| Carbohydrate fermentation pink | Negative test. pH more than 7.4 |
| Carbohydrates fermentation is detected with | phenol red broth |
| Urease test | Differentiates based on the ability to produce the enzyme urease |
| Breaks down urea into ammonia and carbon dioxide | urease |
| Urease test pH Indicator | Phenol red |
| Urease test positive | Pink/red color |
| Urease test negative | Orange/yellow color |
| Methyl red test | Identifies mixed acid fermenters, which produce stable acidic end products |
| Methyl red test positive and negative | •Positive: Red •Negative: Yellow |
| Nitrate reduction test | Detects the ability to reduce nitrate (NO3) to nitrite (NO2), or completely to N2 gas in anaerobic conditions. |
| Nitrate reduction nitrate source | potassium nitrate |
| Biofilm | the growth of a microbial community on a surface |
| Biofilm steps | 1. Reversible attachment 2. Irreversible attachment 3. Maturation I 4. Maturation II 5. Release |
| During stages 3 and 4 the biofilm becomes encased in an | extracellular matrix |
Created by:
Jdwatts5
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