THE PHYLOGENETIC POSITION OF THE FAMILY METHYLOCOCCACEAE

The 16S ribosomal DNA-based phylogenetic positions of various members of the Methylococcaceae (group I methanotrophs) were investigated. The Methylococcaceae as a whole formed a distinct branch in the gamma sub division of the Proteobacteria, and this branch had five distinct subb ranches. On the basis of a number of phenotypic traits, phospholipid f atty acid patterns, and the results of a 16S ribosomal DNA analysis, w e determined that the species belonging to one subbranch, Methylobacte r albus, Methylobacter agilis, and Methylobacter pelagicus, formed a d istinct group that could be differentiated from other members of the g enus Methylobacter, which grouped in an adjacent subbranch. We propose that these species belong to a new taxon, Methylomicrobium gen. nov.