Cable Pili and the 22-Kilodalton Adhesin Are Required for Burkholderia cenocepacia Binding to and Transmigration across the Squamous Epithelium

Abstract

Burkholderia cenocepacia strains expressing both cable (Cbl) pili and the 22-kDa adhesin bind to cytokeratin 13 (CK13) strongly and invade squamous epithelium efficiently. It has not been established, however, whether the gene encoding the adhesin is located in the cbl operon or what specific contribution the adhesin and Cbl pili lend to binding and transmigration or invasion capacity of B. cenocepacia. By immunoscreening an expression library of B. cenocepacia isolate BC7, we identified a large gene (adhA) that encodes the 22-kDa adhesin. Isogenic mutants lacking expression of either Cbl pili (cblA or cblS mutants) or the adhesin (adhA mutant) were constructed to assess the individual role of Cbl pili and the adhesin in mediating B. cenocepacia binding to and transmigration across squamous epithelium. Relative to the parent strain, mutants of Cbl pili showed reduced binding (50%) to isolated CK13, while the adhesin mutant showed almost no binding (0 to 8%). Mutants lacking either cable pili or the adhesin were compromised in their ability to bind to and transmigrate across the squamous epithelium compared to the wild-type strain, although this deficiency was most pronounced in the adhA mutant. These results indicate that both Cbl pili and the 22-kDa adhesin are necessary for the optimal binding to CK13 and transmigration properties of B. cenocepacia.

Mannitol promotes adherence of an outbreak strain of Burkholderia multivorans via an exopolysaccharide-independent mechanism that is associated with upregulation of newly identified fimbrial and afimbrial adhesins

“…Whilst adhesins have been described in other members of the Bcc and within the wider Burkholderia genus (Balder et al, 2010;Mil-Homens et al, 2010;Mil-Homens & Fialho, 2012;Urban et al, 2005), the present study represents the first investigation, to our knowledge, of putative fimbrial and FHA-family adhesins within the Bcc and the first characterization of any specific adhesins within B. multivorans. Whilst fimbrial and FHA-family adhesins are common within the Burkholderia genus, there is considerable diversity at the amino acid level between the adhesins of different species.…”

The Genome of Burkholderia cenocepacia J2315, an Epidemic Pathogen of Cystic Fibrosis Patients

“…The cable pilus gene cluster is located on chromosome 2 and consists of seven CDSs (Table 3), four of which encode structural and processing components (cblDCAB) and three of which encode regulatory components (cblRTS). The pili are arranged as large peritrichous individual fibers 2 to 4 m in length and are associated with a 22-kDa adhesion protein (AdhA) (137). Both the cbl cluster and adhA are in RODs, as is one of the three chaperone-usher-type fimbria clusters contained within the J2315 genome ( Table 3).…”

Molecular Mechanisms of Chlorhexidine Tolerance in Burkholderia cenocepacia Biofilms

“…Another downregulated gene in chlorhexidine-exposed sessile cells was BCAM2143 (2.9-fold downregulated), encoding the 22-kDa adhesion protein AdhA (10). This gene is required for the binding of B. cenocepacia J2315 to cytokeratin 13 and for the efficient invasion of squamous epithelium (32). Twenty genes encoding proteins involved in chemotaxis and motility (functional class 1.1.1; see Table S3 in the supplemental material) were upregulated and included genes encoding the flagellar motor switch proteins FliG, FliN, and FliM (BCAL0524, 2.2-fold; BCAL3505, 3.0-fold; and BCAL3506, 2.4-fold), the M-ring protein FliF (BCAL0525, 3.3-fold), the flagellar basal body rod proteins FlgB, FlgF, and FlgG (BCAL0564, 3.1-fold; BCAL0568, 2.6-fold; and BCAL0569, 2.6-fold), as well as seven (putative) methyl-accepting chemotaxis proteins (upregulated between 2.2-and 8.5-fold; see Table S1).…”