Regulation of Virulence by Endogenous Signal Molecules and the Importance of Extracellular Polysaccharide During Infection and Colonization

Expression of some virulence genes controlled by the global regulator PhcA increases >20-fold during exponential growth of R. solanacearum. These cell density-associated changes suggest that autoregulators may control a shift between low and high virulence phenotypes. Virulence genes are not regulated by acyl homoserine lactones; however, a novel fatty acid autoregulator is essential for normal virulence gene expression. Acidic extracellular polysaccharide Increases bacterial pathogenic/reproductive fitness, since it is required for rapid systemic colonization of tomato plants.