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Biochemical Identification

Closely related organisms can be differentiated using a series of biochemical tests that identify various metabolic properties of different bacterial species.

Table 1: Examples of biochemical tests used to identify bacteria

Table with two columns. The first column is labeled "Biochemical Test", and the second is labeled "Function": motility tests identify the bacteria's ability to move, oxidase tests demonstrate the bacteria's ability to produce cytochrome-c oxidase, glucose fermentation tests determine the ability of bacteria to ferment sugar glucose, nitrate tests determine the ability of bacteria to produce the enzyme nitratase, fluid thioglycollate tests show oxygen usage, urea tests determine the ability of bacteria to produce enzyme urease, indole tests determine the ability of bacteria to produce tryptophanase, Methyl red tests indicate low pH and fermentation ability of bacteria, Voges Proskauer tests determine the ability of bacteria to produce acetoin, and Simmons citrate slant tests demonstrates the ability of gram-negative bacteria to use citrate as an energy source.

Specialized media exists that combines different biochemical identification methods to specifically identify certain genus of bacteria. For example, the Salmonella Shigella agar enables scientist to efficiently test a sample for Salmonella contamination.

The main drawback of biochemical identification methods is they can only be used for organisms that can be cultivated in vitro. If a microorganism cannot be cultivated, molecular methods have to be used for identification.

Referred from:

Article
Cell morphology identification
Article
Differential staining