Phylogenetic analysis and intrageneric structure of the genus Hyphomicrobium and the related genus Filomicrobium

Almost complete 16S rDNA sequences from the type strains of seven species of the genus Hyphomicrobium and of Filomicrobium fusiforme have been determined. The Hyphomicrobium species form two phylogenetic clusters that are only moderately related to each other. While cluster I contains the type species Hyphomicrobium vulgare, Hyphomicrobium aestuarii, Hyphomicrobium hollandicum and Hyphomicrobium zavarzinii, cluster II comprises Hyphomicrobium facilis, Hyphomicrobium denitrificans and Hyphomicrobium methylovorum. Within the two species clusters, the species are highly related. Phylogenetically, Filomicrobium fusiforme clusters moderately with Hyphomicrobium species. The lack of distinguishing phenotypical properties presently excludes the possibility of describing cluster II as a new genus.