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ONPG Test (for β-galactosidase): Use, Principle, Procedure and Result Interpretation
Use of ONPG Test ONPG test is useful in differentiating members of the family Enterobacteriaceae and genera Neisseria based on b-D-galactosidase activity. ONPG stands for o-Nitrophenyl-b-D-galactopyranoside. Principle of ONPG Test The ability of a bacterium to ferment lactose depends on two enzymes and they are permease and b-galactosidase. Permease allows lactose to enter the bacterial cell wall, where lactose is then broken down into glucose and galactose by b-galactosidase. Bacteria can metabolize glucose and galactose. The enzymes are...
Butyrate Disk Test: Introduction, Principle, Procedure, Result and Interpretation
Introduction of Butyrate Disk Test Butyrate disk test is useful to differentiate Moraxella catarrhalis from Neisseria spp. like Neisseria gonorrhoeae, Neisseria lactamica. Principle of Butyrate Disk Test The butyrate disk test is a rapid test for the detection of the enzyme butyrate esterase. Bromochloro-indolyl butyrate (IB) is the substrate. Hydrolysis of the IB substrate by the butyrate esterase of the test organism( M. catarrhalis) releases indoxyl, which in the presence of oxygen spontaneously forms indigo, a...
Gelatin Liquefaction Test: Introduction, Principle, Procedure and Result Interpretation
Introduction of Gelatin Liquefaction Test Gelatin is a solidifying agent and is used in microbiology for culture media before the use of agar. It is nowadays replaced by agar due to having better-solidifying properties than gelatin but even in use for gelatin liquefaction test to identify various organisms like Bacillus, Clostridium, Proteus, Pseudomonas, and Serratia. It is a protein derived from the animal protein collagen– a component of vertebrate connective tissue. Gelatin is a liquid at 28°C...