Peptococcus heliotrinreducans, sp. nov., a cytochrome-producing anaerobe which metabolizes pyrrolizidine alkaloids.

Several strains of a new, obligately anaerobic, Gram-positive coccus were isolated from sheep rumen contents. An important distinctive feature was their reductive cleavage of hepatotoxic pyrrolizidines, using hydrogen gas or formate as hydrogen donor. With the same hydrogen donors, the organism reduced nitrate and fumarate. In all cases, the reductive metabolism formed part of an energy-giving sequence used by the organism for growth. This new coccus also utilized energy obtained by dissimilation of arginine. Enzymic hydrolysates of casein and yeast autolysate were satisfactory substrates for growth but no strain fermented carbohydrates. Ultrasonic extracts of the coccus contained a c-type cytochrome. The characteristics of the organism are consistent with its allocation to the genus Peptococcus within which it differs significantly from currently recognized species. The name Peptococcus heliotrinreducans is proposed for this new species, and a reliable method for isolating it is described.