The hierarchical system of the ‘Alphaproteobacteria’: description of Hyphomonadaceae fam. nov., Xanthobacteraceae fam. nov. and Erythrobacteraceae fam. nov.

Abstract

Phylogenetic analysis of the class ‘Alphaproteobacteria’, including physiologically diverse species, was conducted by using small-subunit rRNA gene sequences. The 16S rRNA gene sequences of 261 species in the class ‘Alphaproteobacteria’ were obtained from GenBank/EMBL/DDBJ for constructing a phylogenetic tree by using maximum-likelihood analysis. In the resulting tree, members of the class ‘Alphaproteobacteria’ were subdivided into five major clusters, which were compared with the taxonomic outline ofBergey's Manual of Systematic Biologyand thearbtree. Based on this phylogenetic tree, three novel families are proposed:Hyphomonadaceaefam. nov. to accommodate the bacterial generaHyphomonas,Hirschia,MaricaulisandOceanicaulis,Xanthobacteraceaefam. nov. to include the generaXanthobacter,Azorhizobium,Ancylobacter,LabrysandStarkeya, andErythrobacteraceaefam. nov. to accommodate the generaErythrobacter,PorphyrobacterandErythromicrobium. The phylogenetic tree of 16S rRNA gene sequences established in this study may provide a sound basis for future taxonomic reconstruction of the class ‘Alphaproteobacteria’.