lab midterm all tests

what does oxidase test test for and how

cytochrome c oxidase

in the presence of the cytochrome c oxidase the reagent is oxidized and turns a dark blue or black

what is the oxidase test indicator

dimethyl-p-phenylenediamine hydrochloride

what does catalase test test for and how

catalase

once H2O2 is added, if bubbling occurs then the microbe has catalase

H2O2 equation, and for what test

H2O2 → 2 H2O + O2

catalase test

what does a nitrate test test for and how

nitrate reductase (nitrate NO3 to nitrite NO2 or N2 gas)

1st round: nitrate I and II added, if it turns brick red its positive

2nd round: Zn added, if it turns brick red its negative

nitrate test reagents

nitrate I: sulfanilic acid

nitrate II: dimethyl-alpha-naphthylamine

Zn

what does urea broth test for an how

urease

degradation of urea into 2 ammonia NH3 and CO2 is alkaline and will turn cerise

urea broth indicator

phenyl red

positive is cerise, negative is yellow

what does a gelatin test test for and how

gelatinase

if gelatin is hydrolyzed into amino acids it will remain liquid and indicates a positive result

what does a phenylalanine slant test for and how

phenylalanine deaminase

phenylalanine is turned into phenylpyruvic acid (PPA) and ammonia (NH3), if positive the slant turns green

phenylalanine slant neumonic

pp in pool turns green

phenylalanine slant reagents

10% ferric chloride (FeCl3)

what three things does a SIM test test for and how

1. sulfide: H2S is produced from bacterium and turns black

2. Indole from tryptophanase

3. motility: turbidity

SIM reagent

Fe in medium- not a reagent but reacts with H2S to form a black precipitate

Kovac’s reagent

what does tryptone broth test for and how

tryptophanase

hydrolyzation of tryptophan produces indole, pyruvate and ammonia NH3; indole reacts to form a cerise ring

tryptone broth reagents

Kovak’s reagent: DMABA (p-dimethylaminobenzaldehyde) and HCl dissolved in amyl or butyl alcohol

what does methyl red test test for and how

mixed acid fermentation

detection of high acid production, a positive result is a red color

methyl red reagent

methyl red

what does a voges-proskauer test tets for and how

2,3-butanediol fermentation

the acetoin intermediate from this fermentation reacts with reagents to produce a red color

voges-proskauer reagents

baritt’s reagents

VP I: alpha naphthol

VP II: KOH

what does a simmons citrate slant test for

citrate as sole carbon source for growth; growth is a positive result and may be accompanied by blue color

simmons citrate slant indicator

bromothymol blue

IMViC

Indole, MR, VP, Citrate

what 4 things does a litmus milk test test for

1. fermentation of lactose- acidic and curding

2. metabolism of proteins- alkaline

3. degradation of casein- proteolysis

4. litmus reduction

what 3 things does a litmus milk test contain

1. lactose

2. casein and other peptones

3. litmus pH indicator

5 reaction of litmus milk test

1. acid production (pink)

2. alkaline production (blue, peptone deamination)

3. curd

4. reduction (white)

5. proteolysis (clearing, degradation of casein)

what three sugars can a phenyl red sugar broth contain

glucose, lactose, mannitol

phenyl red sugar broth indicator

phenol red and durham tube (gas)

phenyl red sugar broth results

red: original state

cerise: peptone degradation releases ammonia

yellow: positive for fermentation of the sugar

what 3 things does Kligler’s iron agar (KIA) test for

1. lactose fermentation; 1.0% lactose

2. glucose fermentation; 0.1% glucose

3. sulfur reduction

(1.0% peptone is also an ingredient)

KIA indicators

phenol red for pH and iron from ferric ammonium citrate

KIA results

yellow: acid is formed from fermentation of glucose and lactose exceeding ammonia produced

black: sulfur reduction produces H2S and combines w/ iron to form precipitate

reversion: 2,3-butanediol fermentation; less stable acids oxidized

half: only glucose is fermented and breakdown of peptones happens at the top where O is; peptone deamination reverses acidification

what type of plate is a lipase plate and what does it test for

differential

tests for enzyme lipase which hydrolyzes fats into glycerol and fatty acids

lipase plate indicator

spirit blue; positive result is dark blue zone around growth

what type of plate is a milk agar plate and what does it test for

differential

tests for enzyme caseinase which hydrolyzes casein into amino acids

milk agar plate results

a clearing means that casein has been broken down (gives milk white color) by caseinase

what type of plate is a starch agar plate and what does it test for

differential

tests for enzyme amylase which breaks starch into simple sugars

what is the indicator for a starch agar plate

gram iodine which reacts with starch to form a purple ring indicating a negative result

a positive result is a clearing around the growth which means amylase has broken the starch down