Question

Is it possible a bacterium that can only grow at the bottom of a tube of thioglycolate broth is also oxidase- positive? Why, or why not? Select one: a. Yes, it is absolutely possible. This bacterium is facultative anaerobic, so it uses oxidase to ferment glucose. b. No, it is not possible. It is an obligate anaerobe, and has no reason to have enzymes needed for aerobic respiration. O c. No, it is not possible. It can only use fermentation to make energy, and should have catalase, not oxidase. d. Yes, it is completely possible. It uses oxidase to detoxify oxygen.

Answer 1

Ans ) The correct answer for this question is -

b) No, it is not possible . It is an obligate anaerobe, and has no reason to have enzymes needed for aerobic respiration.

EXPLANATION -

Thioglycolate broth provide anaerobic medium by removing oxyegen hence help in grow to anaerobic bacteria at bottom. At surface aerobic bacteria grow and allover tube facultative anaerobes grow hence it provide stratification of bacteria.

in this question since bacteria grow at botton of thioglycolate it means it must be anaerobic bacteria.

oxidase test - in this test cytochrome c producer bacteria is oxidase positive and it is the component of ETC hence usually given by aerobic bacteria.

catalase test also given by aerobic bacteria usually.

Conclusion - since it is obligate anaerobes hence also not give oxidase test because it need cytochrome oxidase enzyme which is component of aerobic respiration enzyme. Which not need by obligate anaerobic bacteria . Hence correct option is - b)