A positive gelatin liquefaction is characteristic of which organism?

A positive gelatin liquefaction is characteristic of which organism?

• A. Proteus vulgaris
• B. Serratia liquefaciens
• C. Morganella morganii
• D. Salmonella Typhimurium

Answer: (B)

Gelatin liquefaction tests detect extracellular gelatinase, an enzyme that hydrolyzes gelatin in the medium. When an organism produces this enzyme, the solid gelatin becomes liquid during incubation and stays liquid after chilling, giving a positive result. Serratia liquefaciens is classically known to be gelatinase-positive, so it liquefies gelatin and yields a positive test. The other listed organisms are not the typical examples used to illustrate gelatin liquefaction in standard teaching, with Salmonella Typhimurium not normally showing this trait.

Gelatin liquefaction tests detect extracellular gelatinase, an enzyme that hydrolyzes gelatin in the medium. When an organism produces this enzyme, the solid gelatin becomes liquid during incubation and stays liquid after chilling, giving a positive result.

Serratia liquefaciens is classically known to be gelatinase-positive, so it liquefies gelatin and yields a positive test. The other listed organisms are not the typical examples used to illustrate gelatin liquefaction in standard teaching, with Salmonella Typhimurium not normally showing this trait.