Summary auto-generated
This 1999 study employed a polyphasic taxonomic approach to clarify the phylogeny of prosthecate bacteria formerly classified as Caulobacter species. The researchers analyzed 76 bacterial strains using 16S rDNA sequencing, restriction fragment profiling of 16S-23S rDNA interspacer regions, lipid analysis, immunological profiling, salt tolerance testing, and DNA-DNA hybridization. The results revealed that the genus Caulobacter sensu lato was paraphyletic and required reorganization. The freshwater and brackish-water species were reclassified into the genus Brevundimonas, while the halophilic marine species Caulobacter maris and Caulobacter halobacteroides formed a new genus, Maricaulis gen. nov., with Maricaulis maris designated as the type species. Mycoplana segnis was reclassified as Caulobacter segnis. Additionally, C. crescentus was found to be synonymous with C. vibrioides, and C. halobacteroides was synonymous with Maricaulis maris. Caulobacter leidyia clustered with Sphingomonas species. The study identified distinctive biomarkers for each genus and proposed the necessary taxonomic recombinations to reflect the newly clarified phylogenetic relationships among these oligotrophic aquatic bacteria.
Key findings
- Caulobacter sensu lato is paraphyletic; the genus required subdivision into three distinct genera: Caulobacter sensu stricto, Brevundimonas, and the newly described Maricaulis gen. nov.
- Maricaulis gen. nov. encompasses the halophilic marine species Caulobacter maris (type species) and Caulobacter halobacteroides, which are phylogenetically distinct from freshwater caulobacters.
- Multiple species were reclassified: seven Caulobacter species were transferred to Brevundimonas, Mycoplana segnis became Caulobacter segnis, and several strains were identified as synonymous with existing species.
- Distinct lipid, immunological, and respiratory quinone biomarkers were identified that differentiate the three genera of prosthecate bacteria.
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Abstract
The genus Caulobacter is composed of prosthecate bacteria often specialized for oligotrophic environments. The taxonomy of Caulobacter has relied primarily 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 restriction fragments of 16S-23S rDNA interspacer regions, lipid analysis, immunological profiling and salt tolerance characterizations, was used to clarify the taxonomy of 76 strains of the genera Caulobacter, Brevundimonas, Hyphomonas and Mycoplana. The described species of the genus Caulobacter formed a paraphyletic group with Caulobacter henricii, Caulobacter fusiformis, Caulobacter vibrioides and Mycoplana segnis (Caulobacter segnis comb, nov.) belonging to Caulobacter sensu stricto. Caulobacter bacteroides (Brevundimonas bacteroides comb, nov.), C. henricii subsp. aurantiacus (Brevundimonas aurantiaca comb, nov.), Caulobacter intermedius (Brevundimonas intermedia comb. nov.), Caulobacter subvibrioides (Brevundimonas subvibrioides comb. nov.), C. subvibrioides subsp. albus (Brevundimonas alba comb. nov.), Caulobacter variabilis (Brevundimonas variabilis comb. nov.) and Mycoplana bullata belong to the genus Brevundimonas. The halophilic species Caulobacter maris and Caulobacter halobacteroides are different from these two genera and form the genus Maricaulis gen. nov. with Maricaulis maris as the type specis Caulobacter leidyia was observed to cluster with species of the genus Sphingomonas. Caulobacter crescentus is synonymous with C.vibrioides and C. halobacteroides is synonymous with Maricaulis maris as determined by these analyses and DNA-DNA hybridization. Biomarkers discerning these different genera were determined. The necessary recombinations have been proposed and a description of Maricaulis is presented.