The BvgASR virulence regulon of Bordetella pertussis

The BvgAS two-component system of Bordetella pertussis directly activates the expression of a large number of virulence genes in an environmentally responsive manner. The Bvg + mode also promotes the expression of the phosphodiesterase BvgR, which turns off the expression of another set of genes, the vrg s, by reducing levels of c-di-GMP. Increased levels of c-di-GMP in the Bvg − mode are required, together with the phosphorylated response regulator protein RisA∼P, to activate vrg expression. Phosphorylation of RisA requires RisK, a non-co-operonic sensor kinase, but not its co-operonic sensor kinase RisS which is truncated in B. pertussis but intact in the ancestral B. bronchiseptica . The loss of RisS during evolution of B. pertussis led to the ability to express the vrg s, potentially enhancing aerosol transmission of B. pertussis.