The mutagenesis of a type IV secretion system locus of Piscirickettsia salmonis leads to the attenuation of the pathogen in Atlantic salmon, Salmo salar

We report here the genetic manipulation of P. salmonis by means of the transference of plasmid DNA in mating assays. An insertion cassette was engineered for targeting the icmB gene, which encodes a putative T4SS‐ATPase and is carried by one of the chromosomal T4SS clusters found within the genome of P. salmonis PM15972A1, a virulent representative of the EM‐90‐like strain. The molecular characterization of the resulting mutant strain demonstrated that the insertion interrupted the target gene. Further in vitro testing of the icmB mutant showed a dramatic drop in infectivity as tested in CHSE‐214 cells, which is in agreement with its attenuated behaviour observed in vivo. Altogether, our results demonstrate that, similar to other facultative intracellular pathogens, P. salmonis’ virulence relies on an intact T4SS.

Source: Journal of Fish Diseases - December 18, 2017 Category: Zoology Authors: M Mancilla, J Saavedra, M Grand ón, E Tapia, E Navas, H Grothusen, P Bustos Tags: ORIGINAL ARTICLE Source Type: research