IMVIC Tests, macromolecule hydrolysis, and media review

Describe citrate broth, including

• complex or chemically defined

• main differential component

• enzyme or pathway product

• positive indicator and org

• negative indicator and org

• chemically defined

• citrate permease, pH indicator promothymol blue

• fermentation pathway product, citrate sole carbon srouce

• positive: blue, Enterobacter aerogenes

• negative: green (no color change), Escherichia coli

Describe MRVP broth, including

• complex or chemically defined

• main differential component

• enzyme or pathway product

• positive indicator and org

• negative indicator and org

• complex

• MR: methyl red, acidic pH indicator; VP: KOH

• MR: mixed acid fermentation; VP: butanediol fermentation

• positive: MR: red below 4.4, E. Coli; VP: red, E. aerogenes

• negative: MR: yellow/orange, E, aerogenes; VP: no color change, E. Coli

What IMViC tests are E. aergoenes and E. coli positive/negative for?

• indole

• MR

• VP

• Citrate

• indole: E. coli positive, E. aerogenes negative

• MR: E. coli positive, E. aerogenes negative

• VP: E. coli negative, E. aerogenes positive

• Citrate: E. coli negative, E. aerogenes positive

Describe indole test in tryptone broth, including

• complex or chemically defined

• main differential component

• enzyme or pathway product

• positive indicator and org

• negative indicator and org

• complex

• detects indole with Kovac’s reagent

• tryptophanase present; fermentation

• positive: cherry red, E. Coli

• negative: no color change, E. aerogenes

What are the positive and negatives for the starch agar?

• pos: Bacillus subtilis (halo)

• neg: Escherichia coli (no halo)

What are the positive and negatives for the fat agar?

• pos: Aeromonas hydrophila (hot pink and red)

• neg: Enterobacter aerogenes (amber)

Describe fat agar plates, including

• complex or chemically defined

• main differential component

• enzyme or pathway product

• positive indicator and org

• negative indicator and org

• complex

• lipase secretion

• hydrolysis of fats enzyme

• pos: bright red color change, Aeromonas hydrophila

• neg: amber color, Enterobacter aerogenes

Describe starch agar plates, including

• complex or chemically defined

• main differential component

• enzyme or pathway product

• positive indicator and org

• negative indicator and org

• complex

• secretion of amylase

• sugar hydrolysis enzyme

• pos: halo, Bacillus subtilis

• neg: no halo, Escherichia coli

Describe skim milk agar plates, including

• complex or chemically defined

• main differential component

• enzyme or pathway product

• positive indicator and org

• negative indicator and org

• complex

• secretion of casein

• hydrolysis of milk proteins

• pos: clear zone, Bacillus subtilis

• neg: no zone, Enterobacter aerogenes

Describe Nu-gel broths, including

• complex or chemically defined

• main differential component

• enzyme or pathway product

• positive indicator and org

• negative indicator and org

• complex

• gelatinase

• hydrolysis of gelatin enzyme

• pos: liquid, Bacillus subtilis

• neg: solid, Escherichia coli

What are the positive and negative controls for skim milk plates?

• pos: Bacillus subtilis (zone)

• neg: Enterobacter aerogenes (no zone)

What are the positive and negatives for the nu-gel broth?

• pos: Bacillus subtilis (liquid)

• neg: Escherichia coli (solid)

What are the positive and negative controls for the citrate test?

• pos: E. aerogenes, blue

• neg: E. coli, no color change

How is starch hydrolysis detected?

Starch hydrolysis is detected by adding iodine solution, which will turn blue-black in the presence of starch. A clear zone around the bacterial growth indicates starch has been hydrolyzed.

What was the positive and negative controls for the fat agar?

• pos: Aeromonas hydrophila (red)

• neg: Enterbacter aerogenes (amber)

What were the positive and negative controls for hydrolyzing casein? (Skim milk plate)

• pos: Bacillus subtilis (halo)

• neg: Enterobacter aerogenes (no halo)

What were the positive and negative controls for hydrolyzing gelatin? (Nu-gel broth)

• pos: Bacillus subtilis (liquid)

• neg: E. coli (solid)