Abstract
Ruminal fluid which was enriched with trans-aconitate yielded a gram-negative diplococcus (strain AO) which was identified by 16S ribosomal DNA sequence analysis as Acidaminococcus fermentans. In contrast to the original description, the A. fermentans type strain and strain AO were found to utilize citrate as an energy source and to produce hydrogen and hydrogen sulfide. The descriptions of the genus and species are emended accordingly.