Phylogenetic analyses of Candidatus Branchiomonas cysticola refine the taxonomic classification of Betaproteobacteria associated with epitheliocystis in fish

Arch Microbiol. 2023 May 13;205(6):234. doi: 10.1007/s00203-023-03581-1.

Abstract

Candidatus Branchiomonas cysticola is recognized as the most prevalent bacterial agent causing epitheliocystis in Atlantic salmon (Salmo salar). Based on its partial 16S rRNA sequence, the bacterium has previously been found to be a member of Burkholderiales in the class Betaproteobacteria. Multilocus Sequence Analysis (MLSA) of the bacterium and 60 type strains of Betaproteobacteria using newly identified housekeeping genes (dnaK, rpoC, and fusA) and ribosomal subunit sequences (16S and 23S), instead supported the bacterium's affiliation to Nitrosomodales. Taxonomic rank normalization by Relative Evolutionary Divergence (RED) showed the phylogenetic distinction between Cand. B. cysticola and its closest related type strain to be at the family level. A novel bacterial family named Branchiomonaceae has thus been proposed to include a monophyletic clade of Betaproteobacteria exclusively associated with epitheliocystis in fish.

Keywords: 16S rRNA; Candidatus Branchiomonas cysticola; Epitheliocystis; MLSA; Phylogeny; Relative evolutionary divergence.

MeSH terms

  • Animals
  • Bacterial Infections* / microbiology
  • Betaproteobacteria* / genetics
  • Burkholderiales* / genetics
  • Chlamydiales* / genetics
  • DNA, Bacterial / genetics
  • Fish Diseases* / microbiology
  • Phylogeny
  • RNA, Ribosomal, 16S / genetics
  • Salmo salar*
  • Sequence Analysis, DNA

Substances

  • RNA, Ribosomal, 16S
  • DNA, Bacterial