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

Strain P3-BQ1^T 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 (<i>Salmo salar</i>) during an outbreak of tenacibaculosis in a Chilean fish farm. Phylogenetic analysis based on 16S rRNA gene sequencing confirmed that strain P3-BQ1^T belongs to the genus <i>Tenacibaculum</i> and is most closely related to <i>Tenacibaculum dicentrarchi</i> 35/09^T (98.53%), '<i>Tenacibaculum pacificus</i>' 18-2881-A (98.46%), <i>Tenacibaculum aestuariivivum</i> JDTF-79^T (98.46%), <i>Tenacibaculum finnmarkense</i> TNO010 (97.85%) and <i>Tenacibaculum piscium</i> TNO20^T (97.41%). The genome size of strain P3-BQ1^T 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 <i>Tenacibaculum</i> species, with the closest neighbour being <i>T. dicentrarchi</i> 35/09^T (score 87.41 %). In contrast, P3-BQ1ᵀ and '<i>T. pacificus</i>' 18-2881-A shared a 96.58%, thus exceeding the species threshold. This result is also supported by whole-genome <i>in silico</i> DNA-DNA hybridization/Genome-to-Genome Distance Calculator values, indicating that strains P3-BQ1^T and 18-2881-A are conspecific. Strain P3-BQ1^T contains MK-6 as its sole detectable menaquinone. The polar lipids profile includes glycolipids (<i>n</i>=2), aminolipids (<i>n</i>=3) and unidentified lipids (<i>n</i>=5). The predominant cellular fatty acids (>5 %) are C_{13 : 1}, C_{15 : 0}, iso-C_{15 : 0}, iso-C_{15 : 0} 3-OH and summed feature 3 (C_{16 : 1}ω7с/C_{16 : 1}ω6с). An immersion challenge was conducted to assess the pathogenic potential in Atlantic salmon. Our findings indicate that strain P3-BQ1^T alone does not cause significant mortality, suggesting it is likely non-pathogenic to this species. Based on the phenotypic, phylogenetic and genotypic data presented, <i>Tenacibaculum salmonis</i> sp. nov. is proposed here with type strain P3-BQ1^T (=IMI 507635^T=RGM 3581^T), being 18-2881-A an additional strain.