BIOD 171 LAB 7 EXAM
1. A biochemical test used to identify whether or not a microorganism can breakdown tryptophan is
called the test.
Indole
2. What color would you expect to see on the 4-quadrant enzymatic test card if a microorganism was
unable to breakdown tryptophan?
Yellow. The microorganism would be classified as indole negative.
3. Name one advantage that the ability to breakdown tryptophan brings to a microorganism.
An increased resistance to drugs/medications OR an increased ability to survive harsh
environments—often seen via spore formation.
1. What three sugars are used in the Triple Sugar Iron (TSI) agar?
Glucose, lactose and sucrose.
2. What color is a TSI agar slant containing the negative control? Why?
Red. A TSI agar slant contains 3 sugars and a red pH indicator dye. If none of the sugars have been
fermented (negative control) the pH does not change and the indicator dye stays red. Only when the
sugars present have been fermented does the pH indicator dye turn from red to yellow.
3. Enteric bacteria are often found where? Give an example of one.
Enteric bacteria around found in either the intestines or gut. Examples given in the video were either
Salmonella or Shigella.
1. According to the lab module, which 5 wells of the API strip should be layered with mineral oil?
1. A biochemical test used to identify whether or not a microorganism can breakdown tryptophan is
called the test.
Indole
2. What color would you expect to see on the 4-quadrant enzymatic test card if a microorganism was
unable to breakdown tryptophan?
Yellow. The microorganism would be classified as indole negative.
3. Name one advantage that the ability to breakdown tryptophan brings to a microorganism.
An increased resistance to drugs/medications OR an increased ability to survive harsh
environments—often seen via spore formation.
1. What three sugars are used in the Triple Sugar Iron (TSI) agar?
Glucose, lactose and sucrose.
2. What color is a TSI agar slant containing the negative control? Why?
Red. A TSI agar slant contains 3 sugars and a red pH indicator dye. If none of the sugars have been
fermented (negative control) the pH does not change and the indicator dye stays red. Only when the
sugars present have been fermented does the pH indicator dye turn from red to yellow.
3. Enteric bacteria are often found where? Give an example of one.
Enteric bacteria around found in either the intestines or gut. Examples given in the video were either
Salmonella or Shigella.
1. According to the lab module, which 5 wells of the API strip should be layered with mineral oil?
