Lab 3 Quiz

Question 1

Acid Fast Stain

Answer 1

The Acid fast stain is a differential stain that detects the presence or absence of mycolic acids in the bacterial cell wall.

Question 2

Mycolic Acid

Answer 2

is a waxy material that is found in the genera Mycobacterium and some Nocardia in lesser amounts

The mycolic acid is 50% of the dry weight of the Mycobacterium cells

referred to as “cord factor”

Question 3

SIM MEDIA:

Answer 3

This is a combined media that tests for motility, sulfur reduction to hydrogen sulfide (H2S), and indole production from the amino acid tryptophan.

Question 4

H2S production in SIM

Answer 4

ome bacterial enzymes remove the sulfur from the amino acid cysteine or reduce sulfate directly. Both pathways produce H2S. The SIM media contains ferrous sulfate (iron salts) that will turn black when they combine with H2S gas. Salmonella species often produce H2S.

Question 5

Motility in SIM

Answer 5

Some bacteria are motile by using flagella. The SIM media is used to test for motility by using a needle and inoculating SIM with a stab. If the bacteria swim away from the line of inoculation (stab) they are motile. If the bacteria grow only along the stab line, they are non-motile.

Question 6

Indole production in SIM

Answer 6

Some bacteria produce the enzyme tryptophanase and thus are able to hydrolyze the amino acid tryptophan producing indole and pyruvate. Indole can be detected by the addition of Kovac’s reagent which contains dimethylaminobenzaldehyde (DMABA). When added to the SIM tube, the DMABA reacts with indole and turns cherry red, indicating the presence of rosin dole.