Tenacibaculum salmonis sp. nov., isolated from Atlantic salmon (Salmo salar L.) fish farmed in Chile

TL;DR

A new bacterial species, Tenacibaculum salmonis, was identified from diseased Atlantic salmon in Chile.

Contribution

The discovery of a new non-pathogenic Tenacibaculum species isolated from Atlantic salmon during a disease outbreak.

Findings

Strain P3-BQ1T is phylogenetically distinct from other Tenacibaculum species with OrthoANI scores below 95%.

Genomic and phenotypic analyses confirm P3-BQ1T as a new species, Tenacibaculum salmonis.

The strain is likely non-pathogenic to Atlantic salmon despite being isolated during a disease outbreak.

Abstract

Strain P3-BQ1T is a Gram-negative, aerobic, non-spore-forming bacterium with gliding motility and filamentous cells. It was isolated in 2018 from the gills of a diseased Atlantic salmon (Salmo salar) during an outbreak of tenacibaculosis in a Chilean fish farm. Phylogenetic analysis based on 16S rRNA gene sequencing confirmed that strain P3-BQ1T belongs to the genus Tenacibaculum and is most closely related to Tenacibaculum dicentrarchi 35/09T (98.53%), ‘Tenacibaculum pacificus’ 18-2881-A (98.46%), Tenacibaculum aestuariivivum JDTF-79T (98.46%), Tenacibaculum finnmarkense TNO010 (97.85%) and Tenacibaculum piscium TNO20T (97.41%). The genome size of strain P3-BQ1T is 2,777,603 bp, with a DNA G+C content of 29.18 mol%. The strain has an OrthoANI score lower than 95% compared to the types of all validly named Tenacibaculum species, with the closest neighbour being T. dicentrarchi 35/09T (score 87.41 %). In contrast, P3-BQ1ᵀ and ‘T. pacificus’ 18-2881-A shared a 96.58%, thus exceeding the species threshold. This result is also supported by whole-genome in silico DNA–DNA hybridization/Genome-to-Genome Distance Calculator values, indicating that strains P3-BQ1T and 18-2881-A are conspecific. Strain P3-BQ1T contains MK-6 as its sole detectable menaquinone. The polar lipids profile includes glycolipids (n=2), aminolipids (n=3) and unidentified lipids (n=5). The predominant cellular fatty acids (>5 %) are C13 : 1, C15 : 0, iso-C15 : 0, iso-C15 : 0 3-OH and summed feature 3 (C16 : 1ω7с/C16 : 1ω6с). An immersion challenge was conducted to assess the pathogenic potential in Atlantic salmon. Our findings indicate that strain P3-BQ1T alone does not cause significant mortality, suggesting it is likely non-pathogenic to this species. Based on the phenotypic, phylogenetic and genotypic data presented, Tenacibaculum salmonis sp. nov. is proposed here with type strain P3-BQ1T (=IMI 507635T=RGM 3581T), being 18-2881-A an additional strain.

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