A strong relationship between virulence-associated sensor histidine kinases
of fungi and those in Streptomyces coelicolor was observed, and phylogenet
ic analysis suggested that bacterium-to-eukaryote horizontal gene transfer
had occurred between ancestors of these organisms. Phylogenetic analysis al
so identified a group of histidine kinases orthologous to the Streptomyces
proteins that includes Pseudomonas aeruginosa GacS. We provide evidence tha
t GacS is important for swarming motility, lipase production, and virulence
in mice and had evolved to have partial functional overlaps with PhoQ, a l
ess-related virulence-associated histidine kinase.