Cohabitation of Piscirickettsia salmonis genogroups (LF-89 and EM-90): Synergistic effect on growth dynamics
Piscirickettsia salmonis, the biological agent of SRS (Salmon Rickettsial Syndrome), is a facultative intracellular bacterium that can be divided into two genogroups (LF-89 and EM-90) with different virulence levels and patterns. There are studies that have found co-infection of these genogroups in salmonid farms in Chile, but it is essential to assess whether this competitive interaction within the host is related to virulence and changes in pathogen dynamics. In this work, we studied one isolate from each genogroup, EM-90 and LF-89 . The aim was to evaluate how co-cultures could affect their growth performance and virulence factors expression at in vivo cultures in Atlantic salmon. During in vivo co-cultures, transcriptomic analysis revealed an upregulation of transposases, flagellum-related genes (fliI and flgK), transporters and permeases that could unveil novel virulence effectors used in the early infection process of P. salmonis. Thus, our work has shown that the cohabitation of the genogroups of P. salmonis can modulate their behavior and virulence effectors expression. These data can contribute to new strategies and approaches to improve current health treatments against this salmonid bacterium. Overall design: To investigate the transcriptomic changes of P. salmonis in single cultures compared to co-cultures of both genogroups, we inserted dialysis bags with the bacterial cultures inside Atlantic salmon for 6 days. Then extracted the total RNA to perform an RNA-seq analysis comparing the trasncriptomics profiles of EM-90 alone, LF-89 alone and EM-90 with LF-89 co-cultures.