The gacA gene of Pseudomonas aeruginosa PAO1 is not required for full virulence in Bombyx mori

It is known that the GacS/GacA two-component system is important for the virulence of Pseudomonas aeruginosa in invertebrate and vertebrate hosts and in plants (Rahme et al., 1995; Tan et al., 1999; Jander et al., 2000). In this study, the gacA nonpolar mutant C2 and polar mutant C3 were generated and inoculated into Bombyx mori. The polar mutants showed reduced virulence, whereas no significant difference was observed between the gacA nonpolar mutant and wild type strain with respect to the ability to kill B. mori larvae. This suggests that the reduced virulence was due to a polar effect of the insertions, rather than to the lack of the gacA gene product.