Question

1) Some bacterial pathogens are highly infectious via the respiratory route. Determining whether the pathogen can make an enzyme that breaks down hydrogen peroxide by the catalase method could be hazardous. How? Also include in your answer how the test is performed. (2 pts)

2) Kovac's reagent was used in the indole test. If isoamyl alcohol were not present in the Kovac's reagent, then describe what would be observed following testing of an indole-positive bacterium, and why? Also include in your answer the function of isoamyl alcohol in the test? (2 pts)

Answer 1

1.Escherichia coli produces catalase enzymes, hydroperoxidase I (HPI) and HPII, which catalyze the dismutation of hydrogen peroxide to water and oxygen but these 2 catalases play pivotal roles in protecting cells against the effects of oxidative stress.

There are various pathogenic microorganisms which produces catalase such as staph aureus,bacillus etc

Procedure:Transfer a small amount of bacterial colony to a surface of clean, dry glass slide using a loop or sterile wooden stick,Place a drop of 3% H₂O₂ on to the slide and mix.,A positive result is the rapid evolution of oxygen (within 5-10 sec.) as evidenced by bubbling& negative result is no bubbles or only a few scattered bubbles.Dispose of your slide in the biohazard glass disposal container.

2.Kovacs reagent is a biochemical reagent consisting of isoamyl alcohol.

If isoamyl alcohol is not present then alternative is to use ethyl alcohol or butyl alcohol

If isoamyl alcohol is present then it produces red colour and precipitate which is positive test ,and if it is absent then it produces yellow colour which is a negative test.

Function iof isoamyl alcohol forms a complex with rosindole dye, which causes it to precipitate