GENETIC-REGULATION OF AIRWAY COLONIZATION BY BORDETELLA SPECIES

Bordetella species are respiratory pathogens that infect humans and ot her animals. A majority of the virulence factors expressed by these ba cteria are regulated by a master control locus, BvgAS, a member of the two-component family of signal transduction systems. BvgAS senses env ironmental signals and mediates signal transduction by a phosphorylati on cascade that leads to a biphasic transition between the Bvg(+) and Bvg(-) phases. From natural host studies using Bordetella bronchisepti ca, we have found that expression of Bvg(+) phase factors, which inclu de adhesins and toxins, is required for successful colonization of the mammalian respiratory tract. Suppression of the Bvg(-) phase motility phenotype is necessary for a successful interaction with the host. Al though the Bvg(-) phase does not appear to be required in vivo, it doe s confer the ability to survive under conditions of severe nutrient de privation. We hypothesize that the Bvg(+) phase is necessary and suffi cient for respiratory tract colonization and the Bvg(-) phase is adapt ed for survival in environments encountered during transmission betwee n hosts.