More Than Gliding: Involvement of GldD and GldG in the Virulence of .

A fascinating characteristic of most members of the genus is their ability to move over surfaces by gliding motility. , an important pathogen of farmed salmonids worldwide, contains in its genome the 19 and genes shown to be required for gliding or spreading in ; however, their relative role in its lifestyle remains unknown. In order to address this issue, two spreading deficient mutants were produced as part of a Tn mutant library in strain THCO2-90. The transposons were inserted in and genes. While the wild-type strain is proficient in adhesion, biofilm formation and displays strong proteolytic activity, both mutants lost these characteristics. Extracellular proteome comparisons revealed important modifications for both mutants, with a significant reduction of the amounts of proteins likely transported through the outer membrane by the Type IX secretion system, indicating that GldD and GldG proteins are required for an effective activity of this system. In addition, a significant decrease in virulence was observed using rainbow trout bath and injection infection models. Our results reveal additional roles of and genes that are likely of importance for the lifestyle, including virulence.