Description of Anaerotignum aminivorans gen. nov., sp. nov., a strictly anaerobic, amino-acid-decomposing bacterium isolated from a methanogenic reactor, and reclassification of Clostridium propionicum, Clostridium neopropionicum and Clostridium lactatifermentans as species of the genus Anaerotignum

A strictly anaerobic bacterial strain (SH021T) was isolated from a methanogenic reactor. Cells were Gram-stain-positive, motile, straight or slightly curved rods. The optimum temperature for growth was 35 °C, and the optimum pH was 6.1–7.7. The strain was asaccharolytic and utilized amino acids as growth substrates. The strain produced acetate and propionate from l-alanine and l-serine, and propionate and butyrate from l-threonine. Branched-chain amino acids (l-isoleucine, l-leucine and l-valine) were utilized weakly, and isovalerate or isobutyrate was produced. Strain SH021T utilized pyruvate and lactate, and converted them to acetate and propionate. The genomic DNA G+C content was 38.2 mol%. Compounds related to iso-C15 : 0 were detected as major components in the cellular fatty acids analysis. The diagnostic diamino acid of the cell-wall peptidoglycan was meso-diaminopimelic acid. On the basis of 16S rRNA gene sequences, the most closely related known species were Clostridium propionicum , Clostridium neopropionicum and Clostridium lactatifermentans in cluster XIVb of the class Clostridia . Based on the phylogenetic and phenotypic data, Anaerotignum aminivorans gen. nov., sp. nov. is proposed to accommodate strain SH021T (=JCM 31556T=DSM 103575T). For the three related species of the genus Clostridium , Anaerotignum propionicum comb. nov. (type strain DSM 1682T=JCM 1430T=ATCC 25522T=CCUG 9280T=NCIMB 10656T=VPI 5303T), Anaerotignum neopropionicum comb. nov. (type strain X4T=DSM 3847T=KCTC 15564T) and Anaerotignum lactatifermentans comb. nov. (type strain G17T=DSM 14214T=LMG 20954T) are proposed with emended descriptions of these species.