Phylogeny and polyphasic taxonomy of Caulobacter species. Proposal of Maricaulis gen. nov with Maricaulis maris (Poindexter) comb. nov as the type species, and emended description of the genera Brevundimonas and Caulobacter

The genus Caulobacter is composed of prosthecate bacteria often specialized for oligotrophic environments. The taxonomy of Caulobacter has relied prim arily upon morphological criteria: a strain that visually appeared to be a member of the Caulobacter has generally been called one without challenge. A polyphasic approach, comprising 16S rDNA sequencing, profiling restrictio n fragments of 16S-23S rDNA interspacer regions, lipid analysis, immunologi cal profiling and salt tolerance characterizations, was used to clarify the taxonomy of 76 strains of the genera Caulobacter, Brevundimonas, Hyphomona s and Mycoplana. The described species of the genus Caulobacter formed a pa raphyletic group with Caulobacter henricii, Caulobacter fusiformis, Cauloba cter vibrioides and Mycoplana segnis (Caulobacter segnis comb. nov.) belong ing to Caulobacter sensu stricto. Caulobacter bacteroides (Brevundimonas ba cteroides comb. nov.), C. henricii subsp. aurantiacus (Brevundimonas aurant iaca comb. nov.), Caulobacter intermedius (Brevundimonas intermedia comb, n ov.), Caulobacter subvibrioides (Brevundimonas subvibrioides comb. nov.), C . subvibrioides subsp. albus (Brevundimonas alba comb. nov.), Caulobacter v ariabilis (Brevundimonas variabilis comb. nov.) and Mycoplana bullata belon g to the genus Brevundimonas. The halophilic species Caulobacter maris and Caulobacter halobacteroides are different from these two genera and form th e genus Maricaulis gen. nov, with Maricaulis maris as the type species. Cau lobacter leidyia was observed to cluster with species of the genus Sphingom onas. Caulobacter crescentus is synonymous with C. vibrioides and C. haloba cteroides is synonymous with Maricaulis maris as determined by these analys es and DNA-DNA hybridization. Biomarkers discerning these different genera were determined. The necessary recombinations have been proposed and a desc ription of Maricaulis is presented.