Lab Exam 3- Identifying Tests

MIciroBio

Duham tube fermentation reagent

Phenol red

Durham tube fermentation end-product

acid and/or gas

Durham tube fermentation results

yellow is positive for acid, bubble in tube positive for gas production

Durham tube tests for

the fermentation of carbohydrates (usually sugars)to produce acid and gas.

Mixed acid reagent

methyl red

Mixed acid (MR) results

Yellow is negative, red is positive for mixed acid fermentation, indicating a pH change.

Butanediol (VP) results

opposite of MR result

Catalase Production reagent

H2O2

Catalase production results

bubbling colonies indictae production of catalase when hydrogen peroxide is added.

Oxidase production reagent

known as oxidase reagent

Oxidase results

blue outline forms around the edges indicating posotive for production of oxidase

Starch hydrolysis reagent

iodine

Starch hydrolysis tests for

the production of amylase

starch hydrolysis results

a clear zone around colonies on the agar plate

startch hydrolysis procedure

inoculating starch agar with a microorganism, incubating, and then adding iodine to detect amylase production (clear areas around colony)

Casein hydrolysis media

casin plate

Casin hydrolysis tests for

the production of casinase

Casin hydrolysis results

s

Casin hydrolysis procedure

Inoculate a casein agar plate with a microorganism, incubate it, and observe for clearing around the colonies to indicate caseinase activity. (clear colony = positive)

Fat hydrolysis media

fat hydrolysis plate

Fat hydrolysis tests for

production of lipase

Fat hydrolysis results

observe colony growth, bright pink around colonies is positive, dirty brown colorarion is negative.

Tryptophan hydrolysis (Indole Test) reagent

Kovacs’s reagent

Tryptophan hydrolysis results

a red ring indicates positive indole production, while no color change indicates a negative result.

Trypotophan hydrolysis procedure

Involves inoculating a tryptophan broth and incubating it before adding Kovacs's reagent to observe for a red ring indicating indole production.

Urea Hydrolysis reagent

urea slant

Urea hydrolysis tests for

the production of urease

Urea hydrolysis results

after incubation, color change to pink is positive for urease production

Gelatin Hydrolysis reagent

Gelatin developer

gelatin hydrolysis tests for

production of gelatinase

gelatin hydrolysis results

After incubation, add gelatin developer to colony, a clear zone around colonies on the plate

Citrate utilization reagent

bromthymol blue

Citrate utiliation reasults

A positive result occurs when the medium changes color to blue (due to change in pH), while a negative result remains green.

Phenylalanine deamination reagent

is ferric chloride solution.

Phenylalanine deamination results

A positive result is indicated by the formation of a green color after adding ferric chloride, while a negative result will show no color change.

Glucose Oxidation media

OF medium

Glucose Oxidation results

A positive test has growth with a yellow band at the top of the tube indicating acid production, while a negative test shows no color change or remains green.

Why is the OF medium used in glucose oxidation tests?

OF mediumk is semi-solid and contains a pH indicator, b/c is is semi-solid it trapps CO2 long enough to cause a change to pH and which allows the indicator to change

Nitrate reduction Test 1 reagent

Trammsdorf solution

Which ion does the first nitrate reduction test for?

Nitrite

If the first nitrate test is positive, is there a reduction?

Yes

Nitrate reduction test 2 reagent

Diphenolamine

Which ion does the second nitrate reduction test for?

Nitrate

If the second nitrate reduction test positive, is nitrate reduced?

No