Types of Media – Biochemical Tests – Flashcards
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| What are biochemical tests used for? |
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| used to determine physiological characteristsics of microorganism, particularly in terms of bacterial enzymes and chemistry of biooxidation |
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| What does starch agar test for? |
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| amylase |
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| What does amylase hydrolyze? |
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| starch to simple sugars |
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| What is added to starch plate after incubation? |
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| iodine |
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| If amylase is present in starch agar, what will be observed around an amylase positive colony? |
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| no blue/black colour |
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| What does milk agar test for? |
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| caseinase |
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| What does caseinase hydrolyze? |
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| casein to amino acid products |
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| What is casein? |
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| a primary protein in milk that gives it its white colour |
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| If caseinase is present in milk agar, what will be observed around a caseinase positive colony? |
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| clearing |
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| What does a lipase plate test for? |
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| lipase |
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| What does lipase hydrolyze? |
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| fat to glycerol and fatty acids |
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| What does the production of fatty acids do to pH? |
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| production of fatty acids lowers pH |
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| When lipase is present in the lipase plate, what colour is observed around the lipase positive colony? |
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| dark blue precipitate |
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| What are sugar fermentation tubes used for? |
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| determining if a microorganism can ferment particular sugars |
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| What sugars of interest can sugar fermentation tubes contain? |
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| glucose, lactose, mannitol |
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| What are the three components of a sugar fermentation tube? |
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| sugars of interest, pH indicator, Durham tube |
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| What is the pH indicator of a sugar fermentation tube? |
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| phenol red |
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| If a microorganism is able to ferment the sugar, what will the result of the fermentation produce? |
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| acid |
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| When acid is present in a sugar fermenation tube, what colour indicates that the microorganism is positive for fermentation? |
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| yellow |
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| What is another product that some microorganisms produce during fermentation? |
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| gas |
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| How will the secondary product in sugar fermentation tubes appear in the Durham tube? |
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| a void or bubble |
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| In a sugar fermentation tube, how does an alkaline reaction occur? |
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| utilization of peptone in the broth and not the sugar |
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| If an alkaline reaction occurs, what colour will indicate this? |
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| darkening (red/dark red) |
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| What does Methyl Red (MR) test for? |
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| mixed acid fermentors |
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| What colour indicates a positive Methyl Red test? |
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| red |
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| What does Voges-Proskauer (VP) test for? |
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| 2,3 butanediol fermentors |
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| What do 2,3 butanediol fermentors produce less of compared to mixed acid fermentors? |
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| acid |
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| What is actually tested for in a Voges-Proskauer (VP) instead of a butanediol producer? |
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| acetoin (acetyl methyl carbinol) |
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| What are Barrit's reagents in a VP test? |
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| alpha-napthol and KOH |
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| When oxygen is present in a VP test, what reagent reacts with the product? |
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| KOH |
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| When oxygen is present, what colour indicates that the microorganism is a 2,3 butanediol producer? |
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| brick red colour |
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| What is alpha-naphthol ultimately used for in a VP test? |
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| to intensify the red color |
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| What is an example of a MR + microorganism? |
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| Escherichia |
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| What is an example of a VP + microorganism? |
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| Enterobacter |
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| What are the products of a catalase test? |
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| H2O and O2 |
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| What indicates that the microorganism is catalase positive? |
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| bubbles |
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| What does an oxidase test test for? |
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| oxidase |
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| What products does an oxidase test produce? |
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| coloured products |
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| What aromatic arene does an oxidase test use? |
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| dimethyl-p-phenylenediamine hydrochloride |
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| When oxidase is present, what colour indicates that oxidase is present? |
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| dark blue black |
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| What does nitrate test for? |
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| the ability of microorganisms to reduce nitrate |
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| What is produced in a nitrate test? |
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| N2 + NH3 and other products |
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| What is present in a nitrate broth? |
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| nitrates (NO3-) |
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| What are the reagents in the nitrate test? |
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| sulfanilic acid and dimethyl-alpha-naphthylamine |
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| What colour indicates that the microorganism is nitrate positive? |
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| red |
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| What is added to the tube in a nitrate test if it is yellow? |
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| zinc |
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| What would zinc do to a negative nitrate test? |
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| it will turn red |
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| If the broth does not turn red after the addition of zinc in a nitrate test, what is therefore said about the microorganism? |
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| it is true positive |
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| What happened to the nitrate in a true + Nitrate test? |
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| the nitrate broth was completely reduced to products other than NO2- |
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| What does a indole/tryptophan test test for? |
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| tryptophanase |
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| What does tryptophanase convert tryptophane into? |
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| indole and pyruvic acid |
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| What reagent is added to identify indole in an indole test? |
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| Kovac's Reagent (p-dimethylaminobenzaldehyde, amyl or butyl alcohol, and HCl) |
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| If indole is present, what colour indicates that the microorganism is positive for indole? |
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| red |
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| What does a urea test test for? |
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| urease |
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| What does urease convert urea into? |
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| ammonia and CO2 |
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| If ammonia is present, what happens to the pH of the solution? |
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| increases |
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| If ammonia is present, what colour indicates that the microorganism is urease positive? |
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| red |
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| What does the enzyme cysteine desulfurase remove from cysteine to produce H2S? |
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| sulfur side chain |
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| When H2S is present in a cysteine test, what is produced to indicate an H2S positive test? |
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| black precipitate |
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| What does a SIM test for? |
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| sulfur, indole, and motility |
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| What does a simmons citrate test test for? |
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| utilizes citrate as the sole carbon source |
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| Other than growth, what colour will indicate a citrate positive microorganism? |
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| Prussian blue |
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| What does Phenylalanine test for? |
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| PPA and NH3 |
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| What is added to PPA to indicate presence of products? |
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| ferric chloride |
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| If PPA is present, what colour will indicate a positive phenylalanine test? |
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| deep green |
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| What does litmus milk test for? |
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| lactose fermentation |
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| What kind of reaction causes a pink liquid to form due to a drop in pH from the fermentation of lactose? |
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| acid reaction |
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| What kind of reaction produces a pink solid due to to acid production and coagulation of proteins causing the solid formation? |
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| acid curd reaction |
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| What kind of reaction causes litmus to be reudced and to be colorless (tube appears white since only milk remains)? |
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| reduction |
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| What causes a blue liquid to be produced when protein breakdown produces amino acids that are deaminated and release ammonia? |
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| alkaline reaction |
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| What causes a clearing of medium (may be brown or amber) caused by the enzyme caseinase? |
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| peptonization/proteolysis |
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| What reaction causes the tube to turn white except for a small region at the top where oxygen reoxidizes the litmus to the red coloured form? |
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| acid curd reduction |
