Identifying Gram Negative Bacteria

The following are Gram Negative bacteria we use as unknowns at PGCC.

The following slides will give you the most important characteristics of each species and tests for identification.

Gram negative rod - coliform

Ferments acid and gas from glucose

Ferments acid and gas from lactose

Indole positive

Methyl red positive

Vogues=Proskauer negative

Citrate negative

Gram negative rod - coliform

Ferments acid and gas from glucose

Ferments acid and gas from lactose

Indole negative

Methyl red negative

Voges-Proskauer positive

Citrate positive

Gram negative rod (bacillus) - non-coliform

Ferments acid and gas from glucose

Does not ferment lactose

DNase positive

Growth in bile salts, esculin positive

Produces prodigiosin at 30 degrees, but not at 37 degrees

Gram negative rod

Ferments acid and gas from glucose

Does not ferment lactose

Growth in bile salts, esculin negative

Gram negative rod - non-coliform

Does not ferment carbohydrates

Oxidase positive

Gram negative diplococcus

Oxidase positive