Explain the Importance of Biochemical Tests?

Specific series of biochemical tests have been developed for fast identification of microorganisms in laboratories. These biochemical tests are based on the properties governed by the cell's enzymatic system. Both extracellular (exoenzymes) and intracellular (endoenzymes) enzymes are synthesized by the cell to carry out various biochemical activities. Exoenzymes are released into the environment where these degrade high molecular weight polymers like proteins, carbohydrates etc. into low molecular weight materials. These low molecular weight nutrients are transported into the cell where endoenzymes (functions inside the cell) metabolize them to provide energy and metabolic products. These metabolic products are useful in characterizing the genera. As different microorganisms have different enzymatic profile, these biochemical activities can be used to separate even very closely related microorganisms, e.g. members of enteric bacteria, which you may be aware are a large heterogenous group of microbes present in intestinal tract of humans and other animals. Phenotypically, these are characterized as gram negatives, non-sporulating, non-motile/motile rods which on fermenting sugar produces a variety of end products and usually reduces nitrate to nitrite.

Several members of the enteric group are pathogens and medically important, e.g., Salmonella, Shigella etc.  which causes diarrhoeal illnesses. To combat these infections, quick identification of the pathogen is needed, sometimes even to a species or strain level. Though marked morphologic and genetic relatedness exist among many of the enteric bacteria there is a difference in type and proportion of the fermentation products, produced by them on sugar fermentation and in other biochemical properties. Variety of diagnostic tests and differential media can be used to differentiate among different bacteria. Some more commonly used tests are those for the type of formic acid fermentation, lactose and citrate utilization, indole production, urea hydrolysis etc.  Identification of the bacteria is based on the analysis of a large number of such diagnostic tests, which are specific to the biochemical characteristics of microorganisms. What are these biochemical characteristics? Let us find out.