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BSC Lab test

lab test 2

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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