Question

Based on this information:

An unknown bacteria had the following results for a Litmus Test:

Pink, coagulated solid formed --> Positive for lactic acid formation

Answer the following question:

What result would you expect for a gelatin hydrolysis test? Positive or negative and why?

Answer 1

Fermentation of lactose is demonstrated when the litmus turns pink as a result of acid production. Ans is POSITIVE, because it turns to PINK> If there was no change in colour, its NEGETIVE.

Gelatin hydrolysis test is used to detect the ability of an organism to produce gelatinase (proteolytic enzyme) that liquefy gelatin. Hydrolysis of gelatin indicates the presence of gelatinases.

This process takes place in two sequential reactions. In the first reaction, gelatinases degrade gelatin to polypeptides. Then, the polypeptides are further converted into amino acids. The bacterial cells can then take up these amino acids and use them in their metabolic processes.

Gelatin hydrolysis test is helpful in identifying and differentiating species of Bacillus, Clostridium, Proteus, Pseudomonas, and Serratia.

It distinguishes the gelatinase-positive, pathogenic Staphylococcus aureus from the gelatinase-negative, non-pathogenic S. epidermidis . Gram-positive, spore-forming, rodshaped, aerobic or anaerobic bacteria such as Bacillus anthracis, Bacillus cereus, Bacillus subtilis, Clostridium perfringens and Clostridium tetani, are also positive for gelatin hydrolysis.

The test can also be used to differentiate genera of gelatinase-producing bacteria such Serratia and Proteus from other members of the family Enterobacteriaceae.

Fermentation of lactose of milk with the production of lactic acid is demonstrated when the litmus turns from blue to pink as a result of acid production. The accumulation of acid acts on casein, resulting in formation of clot due to the precipitation of casein as calcium caseinate