The Genera Succinivibrio and Succinimonas

Abstract

The rumen is a strictly anaerobic ecosystem inhabited mainly by bacteria and ciliated protozoa, plus smaller numbers of fungi. Although several hundred or more species of bacteria can be found in this ecosystem, only about thirty species are usually found at high enough levels to be considered of ecological significance. Succinivibrio dextrinosolvens and Succinimonas amylolytica are included in this group of major species, but have not been extensively studied. These two species are usually found in animals fed some grain in their diets. In addition to contributing to ruminal starch digestion, both species produce succinate, a fermentation product, which can be decarboxylated by Selenomonas ruminantium to form propionate, a major ruminal volatile fatty acid. The cells of both species stain Gram negatively and are motile by means of monotrichous, polar flagella. However, S. amylolytica cells are coccoid whereas cells of S. dextrinosolvens are curved rods with tapered ends. At present, these organisms have been isolated mainly from ruminants, but it is reasonable to suspect they may be present in the gastrointestinal tract of other animals.