Question

Give examples of two different biochemical tests that can be used to phenotypically identify microbes.

Answer 1

Biochemical test that can be used to phenotypically identify microbes include test for carbohydrate fermentation and hydrogen sulfide production test.There are many other biochemical tests are also possible.

The carbohydrate fermentation test is used to determine whether a bacteria can utilize a certain carbohydrate or not. It tests for the presence of acid or gas produced from carbohydrate fermentation. The media in each tube contains a single carbohydrate like glucose, lactose, and sucrose. A color change to yellow in the fermentation media indicates a positive test (+). The basis of this change is that fermentation of carbohydrates gives rise to the production of pyruvic acid causing a change in color of the media from purple to yellow due to the reduction in pH below 6.8.

Hydrogen Sulfide (H2S) Production Test. This test determines whether the microbe reduces sulfur-containing compounds to sulfides during the process of metabolism.A second medium is triple sugar iron agar (TSIA), which is also used to detect the ability of the microbe to ferment up to three sugars such as glucose, lactose, and sucrose.

Hydrogen sulphide is a colorless gas, if produced reacts with the metal salt forming visible insoluble black precipitate of ferrous sulphide.