Colony morphology of different Y . ruckeri strains grown on TSA-SDS showing the HSF
phenotypes. Strains were point inoculated and after 120 h at 28°C colonies were photographed. A. Y. ruckeri 150 parental strain. The HSF- phenotype of yraS mutant (HSF-1) (B), and 956 strains (D) changes to HSF+ phenotype (C and E, respectively), when they are complemented by the yraS gene.