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BSC Lab test
lab test 2
| Question | Answer |
|---|---|
| Tests ability of an organism to ferment certain sugars | Fermentation tubes |
| Final electron acceptor of fermentation | small organic molecule |
| Changes the color of the pH indicator in fermentation tubes | acid end-products |
| What happens if results of fermentation tubes aren't read within 24 hours? | The alkaline products from the growth on peptone in the medium will counter the acid from fermentation and lead to a false-negative test |
| pH indicator of fermentation tubes | Phenol red |
| Tubes used in fermentation tests | Durham tubes |
| Purpose of tubes used in fermentation tests | Trap some of any gas produced |
| Observation of fermentation test: yellow broth with bubbles. Interpretation? | fermentation to acid and gas |
| Observation of fermentation test: yellow broth with no bubbles. Interpretation? | fermentation to acid, no gas |
| Observation of fermentation test: red broth, no bubbles. Interpretation? | no fermentation |
| Observation of fermentation test: pink broth, no bubbles. Interpretation? | degradation of peptone, alkaline end products (no fermentation) |
| Test that provides further information about glucose fermenters regarding the fate of pyruvate | MRVP |
| Identifies bacteria that produce large amounts of stable acid end-products from mixed-acid fermentation of glucose from those that produce neutral end-products | Methyl red (MR) test |
| pH indicator that starts off yellow and turns red below pH 4.4 | Methyl Red |
| Identifies organisms that, after fermentation of glucose to an acid, accumulate the neutral end product 2,3-butanediol | Voges-Proskauer (VP) |
| Detect acetoin | VP reagents |
| Precursor of 2,3-butanediol | acetoin |
| Observation of MR test: Red. Interpretation? | Mixed-acid fermentation |
| Observation of MR test: yellow (no change). Interpretation? | no mixed-acid fermentation |
| Observation of VP test: Red. Observation? | acetoin produced |
| Observation of VP test: no change. Observation? | acetoin not produced |
| Test that distinguishes staphylococci from streptococci | Catalase test |
| Converts hydrogen peroxide to water and oxygen gas | catalase |
| Catalase test observation: formation of gas bubbles. Interpretation? | bacteria produce catalase |
| Catalse test observation: no bubbles. Interpretation? | no catalase produced |
| Reaction of staphylococci in catalase test | formation of gas bubbles (catalse produced) |
| Reaction of streptococci in catalase test | no bubbles (no catalase) |
| Test useful in separating enterics from pseudomonads & presumptive identification of neisseria | oxidase test |
| An enzyme found on some aerobic bacteria that transfers electrons from ETC onto oxygen | cytochrome-c oxidasae |
| Test that detects cytochrome-c oxidase | oxidase test |
| How will organisms incapable of aerobic respiration test in the oxidase test? | negative |
| Observation of oxidase test: purple/black. Interpretation? | cytochrome-c oxidase present |
| Observation of oxidase test: no color change. Interpretation? | no cytochrome-c oxidase |
| Test used to distinguish enterics from other gram-negatives by the ability to carry out anaerobic respiration using nitrate as a FEA | nitrate reduction |
| Nutrate reductases reduce: | nitrate to nitrite |
| If no red color forms after nitrate is added, what 2 things could have happened? | 1. nitrite wasn't produced 2. nitrate was reduced past nitrite |
| What is the next step in the nitrate reduction test if no red color forms? | add a pinch of zinc powder |
| What does it mean if a red color forms after adding zinc to the nitrate test? | It is negative for nitrate reductase (because it was reduced by zinc, not by the organism) |
| What does it mean if no red color forms after adding zinc to the nitrate test? | the organism is nitrate reductase positive (it reduced past the nitrite form of nitrogen) |
| What do the reagents of the nitrate reduction test detect? | nitrite |
| Tests for extracellular enzymes that break down organisms into smaller pieces | exoenzyme production |
| amylase | degrades carb starch back to glucose subunits |
| Casease | cuts milk protein (casein) into smaller peptide fragments and amino acids |
| Lipases | degrade lipids (such as tributyrin) back to glycerol and fatty acid components |
| How can you tell if a medium is positive for exoenzymes? | a zone of clearing around the growtn |
| Used to detect the zone of clearing in starch plates (exoenzyme production tests) | Iodine |
| Combines with starch to give a dark blue color in the exoenzyme production test | Iodine |
| When would the area appear clear in an exoenzyme production test? | the starch is gone and there is nothing for iodine to bind to |
| The sole source of carbon and energy in citrate utilization agar | sodium citrate |
| Sole source of nitrogen in citrate utilization agar | ammonium phosphate |
| pH indicator in citrate utilization | Bromthymol Blue |
| Transports citrate into the cell (citrate utilization agar) | citrate permease |
| Observation of citrate test: blue or any growth in absence of color. Interpretation? | citrate was used |
| Observation of citrate test: green and no growtn. Interpretation? | citrate not used |
| Citrate test: what happens when pH increases? | pH indicator turns from green (negative test) to blue (positive test) |
| Test that differentiates among organisms based on their ability to rapidly hydrolyze urea to ammonia and CO2 | Urea hydrolysis |
| Enzyme used in urea hydrolysis | urease |
| What does ammonia do in urea hydrolysis? | raises the pH and turns the Phenol Red to bright pink |
| pH indicator in urea hydrolysis | phenol red |
| Urease tests are often run alongside ____ tests | IMViC |
| What does strong urease activity allow identification of? | proteus (from other enterics) |
| Observation of urea hydrolysis test: bright pink within 24 hours. Interpretation? | rapid urea hydrolysis (strong urease production) |
| Observation of urea hydrolysis test: orange or yellow. Interpretation? | no hydrolysis (no urease) |
| Bacteria that produce trypyophanase convert: | tryptophjan into indole + pyruvtae and ammonia |
| Added to detect indole | Kovac's reagent |
| What will happen to kovac's reagent if indole is present? | it will turn red |
| Positive result of indole test: | red ring at the top of the tube after 4-5 drops of Kovac's reagent |
| Test used to detect bacterial motility | motility test |
| Observation of motility test: growth extending outward from all directions from stab line. Interpretation? | organism is motile |
| Observation of motility test: growth only along the stab line. Interpretation? | organism is not motile |
| IMViC Test | Indole, methyl red, VP test, citrate |
Created by:
beshoe
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