Question

1. Which one of the following tests are similar to one another because they indicate that bacteria that can produce exoenzymes?

a) DNAse and tryptophanase                                   b) Lipase and DNase

c) decarboxylase and casease                                 d) lipase and oxidase

2. If bacteria can make oligo 1,6 gucosidase it is also expressing....................... and you will need................. to prove it.

a) DNAse, methyl red                                          b) amylase, iodine

c) Tryptophanase, iron                                       d) casease, and no indicator

I can ferment glucose and can grow in anaerobic environment via fermentation of this sugar. I also produce purple color in a microbiological test to which oil is added to stimulate the formation of anaerobic environment.

3. What is the substrate of the enzyme, the presence or absence of which will determine whether the test, with the purple color, will be positive or negative

a) glucose            b) amino acid(s)               c) protein                      d) lipids

4. What is the indicator of the test media from question 13.

a) amylase    b) methyl green    c) ferric ammonium citrate    d) bromcresol purple     e) iron

Answer 1

Question 1

Answer: Lipase and DNase

Explanation:

Option A: Not correct because tryptophanase is an endoenzyme.

Option B: The test lipase is used to identify the lipolytic bacteria producing the exoenzyme 'lipase'. DNase test is used for the identification of bacteria which can produce deoxyribonuclease enzyme. It is an exoenzyme.

Option C: Casease or casein hydrolysis test is performed to differentiate the bacteria based on the production of the exoenzyme casease. This enzyme is responsible for degrading casein. Decarboxylase test is used for the differentiation of the endoenzyme decarboxylase producing bacteria.

Option D: Lipase is and exoenzyme and the test is used for the differentiation of lipase producing bacteria whereas oxidase is an endoenzyme.

Therefore the correct answer is option B) Lipase and DNase

Question 2)

Answer: Amylase, Iodine

Explanation:

The main function of amylase enzyme is to catalyse the starch hydrolysis to produce sugar like maltose and glucose. Oligo 1,6 glucosidase is also called as isomaltase, it assist the amylase enzyme to hydrolyze dextrin to produce maltose.

The carbohydrate fermentation test is used to identify the bacteria capable of hydrolyzing starch using the enzyme amylase. In this test iodine is used as an indicator. The organisms producing the enzymes amylase and Oligo-1,6-glucosidase are capable of hydrolyzing the carbohydrate and produce glucose or maltose. The iodine will turn dark blue if starch is present and the no color change in the media represent the starch hydrolyzing activity.

Question 3)

Answer:b) Amino acids

Explanation:

In this test the organism are grown in semi-solid or liquid medium supplemented with 1% amino acid, glucose and  pH indicator bromcresol purple. The Facultatively fermenting bacteria utilizes the glucose present in the media and produce acidic byproducts as a result the color of the media will be yellow. But under anaerobic conditions, the decarboxylase enzyme will become active which acts on the L-amino acids present in the medium and as a result alkaline amine will be formed. This causes the pH indicator to change the color to deep purple.

Question 3:

Answer: d) bromcresol purple.

Explanation:

The bromcresol purple is used as the pH indictor where it turns purple in the alkaline condition (positive test) and yellow under acidic condition (negative test)