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