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Research Article

Reassessment of the Phylogenetic Position of Caulobacter subvibrioides

SLY, L. I., CAHILL, MARIAN M., MAJEED, K., JONES, G.

International Journal of Systematic Bacteriology 1997; 47(1):211 · https://doi.org/10.1099/00207713-47-1-211

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Summary auto-generated

This study reassesses the phylogenetic position of Caulobacter subvibrioides by sequencing the 16S rRNA gene of the type strain ATCC 15264T and analyzing its fatty acid composition. Previous work suggested the organism belonged to the alpha-4 subgroup of Proteobacteria and was distantly related to other Caulobacter species. The new 16S rRNA sequence of ATCC 15264T clusters with other Caulobacter species, showing 95% similarity to Brevundimonas diminuta. However, the original published sequence (from strain CB81) grouped with the alpha-4 subgroup and resembled Sphingomonas adhaesiva. Fatty acid analysis of the type strain revealed the absence of 2-hydroxymyristic acid, a characteristic marker of alpha-4 subgroup members like Sphingomonas. These findings suggest the originally published sequence does not represent C. subvibrioides ATCC 15264T, but rather represents a different organism related to Sphingomonas adhaesiva. The morphology of ATCC 15264T, lacking prosthecate appendages characteristic of alpha-4 members, supports its classification within the Caulobacter group rather than the alpha-4 subgroup.

Key findings

  • 16S rRNA sequencing of C. subvibrioides ATCC 15264T clusters the organism with other Caulobacter species, showing 95% similarity to Brevundimonas diminuta, contradicting previous phylogenetic assignments to the alpha-4 subgroup
  • The originally published 16S rRNA sequence (from strain CB81) does not match the type strain ATCC 15264T and instead represents an organism closely related to Sphingomonas adhaesiva
  • Fatty acid analysis of C. subvibrioides ATCC 15264T lacks 2-hydroxymyristic acid, a signature fatty acid of alpha-4 subgroup members, supporting reclassification with Caulobacter species
  • Morphological characteristics of ATCC 15264T, including prosthecate appendages, align with typical Caulobacter species rather than alpha-4 subgroup members

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Abstract

Determination of the 16S rRNA gene sequence of Caulobacter subvibrioides ATCC 15264T (T = type strain) confirmed that this species is a member of the alpha subclass of the Proteobacteria and showed that it is phylogenetically most closely related to the Caulobacter group comprising the species Caulobacter bacteroides, Caulobacter crescentus, and Brevundimonas (Pseudomonas) diminuta, for which 16S rRNA sequences of the type strains are currently available. The closest known relative of strain ATCC 15264T among these species is B. diminuta (level of direct pairwise sequence similarity, 95%). On the basis of its previously determined 16S rRNA sequence (accession number M83797), C. subvibrioides is most closely related to Sphingomonas adhaesiva in the alpha-4 subgroup (level of similarity, 97.7%). Analysis of the hydroxy fatty acids of C. subvibrioides ATCC 15264T showed that the 2-hydroxymyristic acid which is characteristic of the genus Sphingomonas was absent.