Lessons learned from the genome analysis of Ralstonia solanacearum

Ralstonia solanacearum is a devastating plant pathogen with a global distribution and an unusually wide host range. This bacterium can also be free-living as a saprophyte in water or in the soil in the absence of host plants. The availability of the complete genome sequence from strain GNU 1000 provided the basis for an integrative analysis of the molecular traits determining the adaptation of the bacterium to various environmental niches and pathogenicity toward plants. This review summarizes current knowledge and speculates on some key bacterial functions, including metabolic versatility, resistance to metals, complex and extensive systems for motility and attachment to external surfaces, and multiple protein secretion systems. Genome sequence analysis provides clues about the evolution of essential virulence genes such as those encoding the Type III secretion system and related pathogenicity effectors. It also provided insights into possible mechanisms contributing to the rapid adaptation of the bacterium to its environment in general and to its interaction with plants in particular.