Regulation of Bacterial Virulence

Bacterial virulence is regulated to infect hosts effectively.

Pathogens often use two-component systems that sense environmental cues like changing temperatures and adjust gene expression.

For example, Bordetella pertussis uses the BvgAS two-component system.

It consists of two proteins: BvgS, a membrane-bound sensor kinase, and BvgA, a cytoplasmic response regulator.

At 37 °C, when Bordetella senses host-like conditions, BvgS autophosphorylates its cytoplasmic domain and transfers the phosphate to BvgA.

This initiates the Bvg+ phase, where virulence genes are activated to express adhesins, toxins, and secretion systems.

Under non-inducing signals like low temperature, BvgS remains inactive.

This triggers the Bvg- phase, where unphosphorylated BvgA represses virulence genes, aiding survival outside the host.

Limited BvgA phosphorylation triggers the intermediate Bvgi phase, activating a subset of virulence genes, such as adhesins, to fine-tune infection under favorable conditions.