Syntrophomonas wolfei subsp. methylbutyratica subsp. nov., and assignment of Syntrophomonas wolfei subsp. saponavida to Syntrophomonas saponavida sp. nov. comb. nov.

A spore-forming bacterium strain 4J5T was isolated from rice field mud. When co-cultured with Methanobacterium formicicum DSM 1535T, strain 4J5T could syntrophically degrade saturated fatty acids with 4–8 carbon atoms, including 2-methylbutyrate. Phylogenetic analysis based on 16S rRNA gene similarity showed that strain 4J5T was most closely related to Syntrophomonas wolfei subsp. wolfei DSM 2245T (98.9% sequence similarity); however, it differed from the latter in the substrates utilized and its genetic characteristics. Therefore, a new subspecies Syntrophomonas wolfei subsp. methylbutyratica is proposed. The type strain is 4J5T (=CGMCC 1.5051T=JCM 14075T). Furthermore, based on 16S rRNA sequence divergence and substrate utilization, we propose the assignment of Syntrophomonas wolfei subsp. saponavida DSM 4212T to Syntrophomonas saponavida sp. nov. comb. nov.