Multilocus sequence analysis reveals different lineages of Pseudomonas anguilliseptica associated with disease in farmed lumpfish (Cyclopterus lumpus L.).

Even Bysveen Mjølnerød,Felix Scholz,Jesús Ángel López Romalde,Snore Gulla,Hanne Katrine Nilsen,Andreas Riborg,Debes Christiansen,Tom Wiklund,Kirsten Liland Bottolfsen,Duncan John Colquhoun

doi:10.1371/journal.pone.0259725

Abstract

The bacterium Pseudomonas anguilliseptica has in recent years emerged as a serious threat to production of lumpfish in Norway. Little is known about the population structure of this bacterium despite its association with disease in a wide range of different fish species throughout the world. The phylogenetic relationships between 53 isolates, primarily derived from diseased lumpfish, but including a number of reference strains from diverse geographical origins and fish species, were reconstructed by Multi-Locus Sequence Analysis (MLSA) using nine housekeeping genes (rpoB, atpD, gyrB, rpoD, ileS, aroE, carA, glnS and recA). MLSA revealed a high degree of relatedness between the studied isolates, altough the seven genotypes identified formed three main phylogenetic lineages. While four genotypes were identified amongst Norwegian lumpfish isolates, a single genotype dominated, irrespective of geographic origin. This suggests the existence of a dominant genotype associated with disease in production of lumpfish in Norwegian aquaculture. Elucidation of the population structure of the bacterium has provided valuable information for potential future vaccine development.

Highlights

Given the genetic and serological diversity demonstrated within the species and existence of both species-specific variants and broad host range variants, the aim of the present study was to elucidate the phylogenetic relationships amongst Norwegian isolates of P. anguilliseptica isolated from farmed lumpfish
Phylogenies inferred from Multi-Locus Sequence Analysis (MLSA) based on nucleotide sequences revealed seven genotypes distributed amongst three major lineages (Fig 1)
Inspection of the tree shows that lumpfish-isolates are dispersed thoughout depending on country of origin (i.e. Norwgian isolates in lineages 1 and 2, Faroese in lineage 1 and Irsish in lineages 1 and 3), while isolates from other fish species belong almost exclusively to lineage 1

Summary

Introduction

Genotyping of Pseudomonas anguilliseptica from farmed lumpfish not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section. Dr Felix Scholz and Andreas Riborg are employed by separate commercial companies (FishVet Group and Vaxxinova AS) and solely provided support of academic relevance.

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Discussion

Conclusion