results lab Flashcards
(Starch)
Negative: Starch in the presence of iodine will impart a blue-black color to the medium indicating the absence of starch-splitting enzymes and representing a negative result
Positive: if starch has been hydrolyzed a clear zone of hydrolysis will surround the growth of the organism
Extracellular Enzymatic Activites of MOs Results(Lipid)
POS: loss of opacity is the result of the hydrolytic reaction yielding soluble glycerol and fatty acids
NEG: The absence of lipolytic eznymes, the medium retains its opacity
Extracellular Enzymatic Activities of MOs Results (Casein)
POS: Organisms secreting proteases will exhibit a zone of proteolysis which is demonstrated by a clear area surrounding the bacterial growth. This is a result of a hydrolytic reaction yielding soluble, noncoloidial amino acids.
NEG: in the absence of protease activity the medium surrounding the growth of the organism remains opaque
Triple Sugar Iron test Results
Red/Yellow: only glucose so the organisms preferentially degrade glucose first. The small amount of acid produced on the slant surface is oxidized rapidly. The butt is maintained because of reduced oxygen tension and slower growth of the organisms
TSIT Yellow/Yellow
lactose and or sucrose fermentation. These substances are present in higher concentrations, they serve as substrates for continued fermentative activities with maintenance of an acid reaction in both slant and butt
TSIT RED/ RED
No carbohydrate fermentation. Peptones are catabolized under anaerobic and/or aerobic conditions resulting in alkaline ph due to production of ammonia.
indole
POS: The substrate tryptophan was hydrolyzed producing indole. Cherry red color
Neg: tryptophan was no hydrolyzed.
methyl red
The ph indicator methyl red detects the presence of large concentrations of acid ends products
Pos: 4.4 ph or lower the indicator will be red
Neg: 6.2 ph or higher has presence of acid but with lower hydrogen ion concentration. Indicator turns yellow
Voges Proskauer Test
POS: Detection of acetylmethycarbinol requires this end product to be oxidized to a diacetyl compound. this reaction will occur in the presence of the a napthol catalyst and a guaninide group that is present in the peptone of the mr-vp medium. A pink complex is formed imparting a rose color to the medium
Citrate Utilization Test
The medium becomes alkaline and the c02 that is generated combines with sodium and water to form sodium carbonate.
Nitrate Reduction
NEG: Cultures not producing a color change means 1. nitrates were not reduced by the organism 2. The organism possessed such potent nitrate reductase enzymes that nitrates were rapidly reduced beyond nitrites to ammonia or molecular nitrogen
The zinc is to determine whether or not nitrates were reduced past the nitrate stage.
Urease Test
POS: As the substrate urea is split into its products, the presence of ammonia creates an alkaline enviorment that causes the phenol red to turn into deep pink.
NEG: failure of deep pink color
Catalase Test
catalayse production can be determined by adding the substrate h202 to an appropriately incubated tyrpticase soy agar slant culture. without catalyase the toxic concentration of h202 cannot be degraded when these organisms are in the presence of oxygen
POS: if present the chemical reaction is indicated by bubbles of free oxygen
Neg: absence of bubbles
Oxidase Test
ability of bacteria to produce cytochrome oxidase can be determined by the addition of the test reagent p-aminodimethylaniline oxalate to colonies grown on a plate medium
This light pink substrate serves as an artificial substrate donating electrongs and theryby becoming oxidized to a blackish compound in the presence of oxidase and free oxygen
POS: following the add of test reagent the development of pink, then maroon, and finally dark purple coloration on the surface of the colonies is indicative of cytochrome oxidase production
Neg:no color change or a light pink coloration on the colonies, is indicative of the absence of oxidase activity
h2s
Can be produced by the reduction of organic sulfur present in the amino acid cysteine
may be produced by the reduction of inorganic sulfur compounds
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