Differential Bvg-Phase Dependent Regulation and Combinatorial Role in Pathogenesis of Two Bordetella Paralogs, BipA and BcfA

Department of Microbiology and Immunology, Program in Molecular Genetics, Wake Forest University Health Sciences, Medical Center Blvd., Winston-Salem, NC. 27157; Genome Damage and Stability Centre, University of Sussex, Science Park Rd., Falmer, Brighton, United Kingdom, BN19QG

^* To whom correspondence should be addressed. Email: rdeora{at}wfubmc.edu.

	Abstract

To successfully colonize their mammalian hosts many bacteria produce multiple virulence factors that play essential roles in disease processes and pathogenesis. Some of these molecules are adhesins that allow efficient attachment to host cells, a prerequisite for successful host colonization. Bordetella spp. express a number of proteins which either play a direct role in attachment to the respiratory epithelia or exhibit similarity to previously known bacterial adhesins. One such recently identified protein is BipA. Despite similarity to intimins and invasins, its deletion from B. bronchiseptica did not result in any significant defect in respiratory tract colonization. In this study, we report the identification of an ORF in B. bronchiseptica, designated as bcfA (Bordetella colonization factor A) that is similar to bipA. In contrast to maximal expression of bipA in the Bvgⁱ phase, bcfA is expressed at high levels in both the Bvg⁺ and the Bvgⁱ phases. We show that BvgA and BvgA-P bind differentially to the bcfA promoter region. Utilizing immunoblot assays, we demonstrate that BcfA is localized to the outer membrane and that it is expressed during animal infection. While individual deletions of either bipA or bcfA does not significantly impact respiratory tract colonization, concomitant deletion of both results in a defect in colonization of the rat trachea. Our results highlight a combinatorial role for two paralogous proteins in mediating efficient respiratory tract colonization.