Nutritional features of the intestinal anaerobe Ruminococcus bromii

Of six strains of Ruminococcus bromii studied, five grew in a minimal chemically defined medium containing minerals, NH(4) (+) as nitrogen source, sulfide or sulfate as sulfur source, fructose as energy and carbon source, isobutyrate or 2-methylbutyrate and carbonic acid-bicarbonate as additional carbon sources, and the vitamins biotin, riboflavin, pyridoxine, vitamin B(12) (replaced by L-methionine), pantethine, and tetrahydrofolate. The strains also could utilize cysteine or thiosulfate but not methionine; and strain Z3 failed to use dithiothreitol, thioglycolate, sulfite, or beta-mercaptoethanol as sole sources of sulfur. Mixtures of amino acids, peptides (Casitone), urea, nitrate, asparagine, or glutamine failed to replace NH(4) (+) as N source. Three strains isolated from Americans were identical in nutritional features, whereas one from a Japanese and one from a South African native differed slightly in having requirements for fewer vitamins. One strain from the cecum of a sow grew well in a rumen fluid-supplemented medium but not in the various chemically defined media plus Casitone. The nutritional features suggest that the environment which selects R. bromii contains relatively little amino acid nitrogen and a relatively large amount of NH(4) (+)-N and indicate that these bacteria must depend upon other bacteria such as those that produce NH(4) (+) from urea or protein and those that produce branched-chain volatile acids to grow.