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.

Candidatus Branchiomonas cysticola 被认为是导致大西洋鲑鱼 ( Salmo salar )上皮囊肿的最普遍的细菌病原体。根据其部分 16S rRNA 序列，该细菌先前已被发现是 Betaproteobacteria 类伯克氏菌目中的一员。使用新发现的管家基因（ dnaK、rpoC和fusA）和核糖体亚基序列（16S 和 23S）对该细菌和 60 种 Betaproteobacteria 菌株进行的多位点序列分析 (MLSA)支持该细菌与 Nitrosomodales 的隶属关系。通过相对进化分歧 (RED) 进行的分类等级归一化显示了Cand之间的系统发育差异。B. cysticola 及其最接近的相关型菌株在科级。因此，提出了一个名为Branchiomonaceae的新细菌家族，其中包括与鱼类上皮囊肿完全相关的 Betaproteobacteria 的单系进化枝。