Functional characterization of the BvgAS two-component system of Bordetella holmesii.

The BvgAS two-component system is the master regulator of virulence gene expression in the mammalian pathogens Bordetella pertussis, Bordetella parapertussis and Bordetella bronchiseptica. This paper reports the partial cloning and characterization of the bvgAS loci of the 'new' Bordetella species Bordetella holmesii, Bordetella trematum and Bordetella hinzii, which are increasingly recognized as opportunistic pathogens in humans. It is demonstrated that the cytoplasmic signalling domains of the BvgS histidine kinases of B. pertussis and B. holmesii are functionally interchangeable, while signal perception by the two sensor proteins seems to be different. Furthermore, it is shown that, despite the high similarity of the BvgA proteins of B. pertussis and B. holmesii, promoter recognition by the response regulator proteins differs substantially in these organisms.