Biochemical tests are laboratory procedures that use specific chemical reactions to identify and characterize microorganisms, such as bacteria. These tests are often used to identify the presence of specific enzymes or metabolic pathways in a microorganism, which can help to distinguish it from other microorganisms.
Some common biochemical tests used in bacteriology include:
Oxidase test: This test is used to detect the presence of the enzyme cytochrome oxidase, which is involved in the metabolism of oxygen.
Catalase test: This test is used to detect the presence of the enzyme catalase, which helps to break down hydrogen peroxide.
Indole test: This test is used to detect the presence of the enzyme tryptophanase, which breaks down the amino acid tryptophan.
Nitrate reduction test: This test is used to detect the ability of a microorganism to reduce nitrate to nitrite.
Gelatinase test: This test is used to detect the ability of a microorganism to produce the enzyme gelatinase, which breaks down gelatin.
These are just a few examples of the many different biochemical tests that are used in bacteriology. Biochemical tests can be useful for identifying and classifying bacteria, and for understanding their metabolism and ecological role.
The o-Nitrophenyl-β-D-Galactopyranoside (ONPG) test is a biochemical test used for the detection of the enzyme β-galactosidase in bacteria. It is mainly applied for differentiating late lactose fermenting organisms from non-lactose fermenters. It is based on the ability of the organism to hydrolyse a synthetic lactose analogue when the required enzyme is present. The test is … Read more
The ability to develop in the presence of varying concentrations of sodium chloride (NaCl) has been used to distinguish between various bacteria.
The Sulfur Reduction Test is the biochemical procedure that is used to detect whether a microorganism is capable of reducing the sulfur-containing compounds to produce hydrogen sulfide (H₂S). It is the process which mainly helps in identifying members of Enterobacteriaceae where some bacteria like Salmonella, Proteus and Citrobacter are able to form the gas during … Read more
Growth at 42°C test is a physiological test used in microbiology for the identification and differentiation of certain non-fermentative Gram-negative bacteria. It is the process where the organism is tested for its ability to grow and survive at a higher temperature of 42°C. This test is mainly applied for the differentiation of Pseudomonas aeruginosa from … Read more
The MRS formulation was made by de Man, Rogosa, and Sharpe to replace a variable product (tomato juice) and give lactobacilli in general a good place to grow.
Lysine decarboxylase test relies on the capability of certain bacteria to degrade L-lysine into caverine after the release of carbon dioxide.
The starch hydrolysis test is a biochemical test which is used to determine the ability of microorganism to hydrolyze starch. It is also referred to as amylase test. It is the process in which extracellular enzymes are produced by the bacteria to break down starch into simpler sugars. These enzymes include α-amylase and oligo-1,6-glucosidase. Starch … Read more
Decarboxylase Test Medium base is used to distinguish bacteria based on their ability to decarboxylate amino acids.
It is a specific colour reaction used for the detection of amino acid tryptophan present in proteins. This test is also referred to as Adamkiewicz–Hopkins reaction or glyoxylic acid test. It is based on the presence of indole ring which is a characteristic structure of tryptophan and not found in other amino acids. Hence the … Read more
Some bacteria make substances that other bacteria need to grow. The X factor and the V factor are two such substances. The heat-stable X-factor can be protoporphyrin IX, hemin, or other iron-containing porphyrins. It can be found in red blood cells and outside of them in the blood. The heat-sensitive V-factor may be nicotinamide adenine dinucleotide (NAD) or nicotinamide adenine dinucleotide phosphate (NADP), and it is mostly found inside red blood cells. The X and V factor test or a disc test can be used to find out if a bacterium depends on its X factor or its V factor. The results can help identify the bacteria.
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