These are Gram-positive, non-sporing non-acid fast cocci. They are strict anaerobes and are generally nonhalophylic with a wide growth range depending on the group. Some will grow on the most simple bacteriological media, while special nutrients are required by others. These may include vitamins, other cofactors and amino acids. Many metabolize peptones and amino acids. Some require fermentable carbohydrates. A variety of biochemical activities are noted in this family, including some fermenters, some produce indole, reduce nitrate, produce urease, coagulase or catalase etc. Peptococcus is the type genus. The other genera include Peptostreptococcus, Sarcina and Coprococcus. Most of these include a wide variety of species.

Genera

Peptococcus: This includes only one species, P. niger. The cocci are arranged as diplococci, irregular clumps or regular clusters. They are anaerobic and n-caproic acid and butyric acid are the main metabolic products.

Peptostreptococcus: This genus consists of three groups of species. Ps. anaerobius is the only representative of one group. It is biochemically similar to P.niger, but grows confluently on commercial media. It forms short chains. The other two groups, which tend to form clumps and clusters; some species form diplococci, which are distinguished by their ability to form butyrate or not. Each group includes about five-six species, which are differentiated on their morphology and biochemical reactions including fermentation, reduction of nitrate, production of indole, urease, coagulase or catalase etc.

Ruminococcus:

Sarcina :

Coprococcus:

Species Profiles

P. Niger

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