Bichemical Tests

Question 1

Acetoin/VP:
Tests organism to see if it can:
Positive results:
Negative result:
Reagent:
Bacteria positive:
Bacteria negative:

Answer 1

Ferment glucose using the butanediol fermentation pathway.
Positive: red color
Negative: no color development
Reagent: VP A (5% a-Naphtol), and VP B (40% KOH)
Positive: Enterobacter, Klebsiella
Negative: E. Coli

Question 2

Catalase test:
Tests organism to see if it can:
Positive results:
Negative result:
Reagent:
Positive bacteria:

Answer 2

Possesses catalase (enzyme covert’s hydrogen peroxide into water and O2), not in obligate anaerobes!
Positive: bubbling
Negative: no bubbles
Reagent: hydrogen peroxide.
Positive: staphylococcus species

Question 3

Citrate test:
Tests organism to see if it can:
Positive results:
Negative result:
Reagent:
Positive bacteria:

Answer 3

Can utilize citrate as a soul carbon/energy source,
Positive: Visible growth with or without blue color, (turns blue indicates consumption of acid substrate.)
Negative: no growth
Reagent: Simmons citrate slant
Positive bacteria: Enterobacter or Klebsiella

Question 4

Fermentation test:
Tests organism to see if it can:
Positive results:
Negative result:
Reagent:
Lactose ferment:
Glucose ferment:

Answer 4

Ferments carbohydrates:
Positive: A (Acid(golden pH indicator into pink)), or AG (turned pink again with gas bubble in Durham thing)
Negative: no color change or gas.
Reagent: NB with pH indicator and specific carbohydrate being tested.
Lactose ferment: E. Coli, Enterobacter, Klebsiella: A/G
Glucose: proteus, pseudomonas aeruginosa

Question 5

Gelatin hydrolysis:
Tests organism to see if it can:
Positive results:
Negative result:
Reagent:

Answer 5

Hydrolyze gelatin: (expresses gelatinase)
Positive: liquid gelatin deep
Negative: solid gelatin deep
Reagent: gelatin deep.

Question 6

Indole:
Tests organism to see if it can:
Positive results:
Negative result:
Reagent:
Positive test:

Answer 6

Possesses tryptophanase. (Required for catabolism of tryptophan.)
Positive: pink top layer
Negative: yellow-brown top layer
Reagent: inoculated into tryptone broth, after incubation add Kovaks reagent to culture and mix well.
Positive test: E. Coli

Question 7

Methyl red (MR):
Tests organism to see if it can:
Positive results:
Negative result:
Reagent:
Positive test!

Answer 7

Uses a mixed acid fermentation pathway. Essentially a pH test to determine if an organism has produced high levels of acid from the fermentation of glucose.
Positive: red color
Negative: yellow color
Reagent: inoculate in glucose peptone broth and incubate, after add methyl red solution and shake. Color of whole tube.
Positive: E.COLI

Question 8

Motility:
Tests organism to see if it can:
Positive results:
Negative result:
Reagent:
Positive test:

Answer 8

Motile vs non-motile: (in solution concentrated just enough for flagellated bacteria to move, medium has redox sensitive dye that is colorless until reduced into red).
Positive: pink growth spreading from red line.
Negative: red line of growth.
Reagent: agar deep.
Positive test: E. Coli (most strain), Enterobacter aerogenes, proteus, pseudomonas aeruginosa.

Question 9

Oxidase test:
Tests organism to see if it can:
Positive results:
Negative result:
Reagent:
Positive test!

Answer 9

Processes cytochrome C oxidase. (Terminal oxidase in the electron transport changes of certain aerobic respires.)
Positive: bright pink (immediately)
Negative: no color change)
Reagent: filter paper with oxidase reagent on it)
Positive: pseudomonas aeruginosa