Considerations on the Identity and Diversity of Organisms Affiliated with Sphingobacterium multivorum-Proposal for a New Species, Sphingobacterium paramultivorum.

Abstract

Plant biomass offers great potential as a sustainable resource, and microbial consortia are primordial in its bioconversion. The wheat-straw-biodegradative bacterial strain w15 has drawn much attention as a result of its biodegradative potential and superior degradation performance in bacterial-fungal consortia. Strain w15 was originally assigned to the species Sphingobacterium multivorum based on its 16S ribosomal RNA (rRNA) gene sequence. A closer examination of this taxonomic placement revealed that the sequence used has 98.9% identity with the ‘divergent’ 16S rRNA gene sequence of S. multivorum NCTC 11343T, yet lower relatedness with the canonical 16S rRNA sequence. A specific region of the gene, located between positions 186 and 210, was found to be highly variable and determinative for the divergence. To solve the identity of strain w15, genome metrics and analyses of ecophysiological niches were undertaken on a selection of strains assigned to S. multivorum and related species. These analyses separated all strains into three clusters, with strain w15, together with strain BIGb0170, constituting a separate radiation, next to S. multivorum and S. siyangense. Moreover, the strains denoted FDAARGOS 1141 and 1142 were placed inside S. siyangense. We propose the renaming of strains w15 and BIGb0170 as members of the novel species, coined Sphingobacterium paramultivorum.