B-245. Identification of a Putative Biofilm Associated Protein on the Surface of Gardnerella vaginalis

J. Patterson, P. Girerd, K. Jefferson;
Virginia Commonwealth Univ., Richmond, VA.

Bacterial vaginosis (BV) is the most common vaginal disorder worldwide. While the etiology of this polymicrobial infection remains poorly characterized and the causative agent is not definitively known, Gardnerella vaginalis predominates in most infections. G. vaginalis has been shown to form a biofilm on the vaginal epithelium of infected women. The biofilm phenotype is associated with elevated resistance to antibiotics, the immune system, and other physical and chemical insults and therefore likely plays a role in the persistence of G. vaginalis during BV. In this study we sought to characterize G. vaginalis biofilms. The biofilm matrix, which holds the bacterial community together and helps to protect it from external insults, can be composed of polysaccharide, protein and/or nucleic acid. We found that G. vaginalis biofilms were dispersed by proteinase K but not by DNaseI or sodium metaperiodate, suggesting that the major adhesin within the biofilm matrix is a protein rather than DNA or polysaccharide. A number of protein intercellular adhesins required in biofilm formation fall within the Biofilm Associated Protein or Bap family of proteins. These large proteins are cell wall-associated with an internal repeat region containing Rib domains. We found a partial gene sequence within the incomplete genome of G. vaginalis (Gardnerella vaginalis Genome Project, Stanford Genome Technology Center) that encodes a protein of similar size, with three Rib domains, and 41% homology to a Bap-family protein from Lactobacillus reuteri and 32.3% homology to the staphylococcal Bap protein, which we refer to as BapL for Bap-like. We completed the sequence analysis of this gene in a clinical isolate using genome walking. We hypothesized that BapL would localize to the surface of G. vaginalis and would be expressed in biofilm cultures. We found, using real time RT-PCR, that bapL expression is significantly elevated under conditions that promote the biofilm phenotype relative to planktonic cultures. We expressed a portion of BapL in E. coli and used it to generate rabbit polyclonal antiserum. Immuno-fluorescence microscopy using the polyclonal antibodies confirmed expression of BapL on the surface of G. vaginalis.