The Bep gene cluster in Burkholderia cenocepacia H111 codes for a water-insoluble exopolysaccharide essential for biofilm formation

Burkholderia cenocepacia is an opportunistic pathogen isolated from cystic fibrosis patients where it causes in-fections that are extremely difficult to treat with antibiotics, and sometimes have a fatal outcome. Biofilm is a virulence trait of B. cenocepacia, and is associated with infection persistence and increased tolerance to antibi-otics. In biofilms exopolysaccharides have an important role, conferring mechanical stability and antibiotic tolerance. Two different exopolysaccharides were isolated from B. cenocepacia H111 biofilms: a water-soluble polysaccharide rich in rhamnose and containing an L-Man residue, and a water-insoluble polymer made of glucose, galactose and mannose. In the present work, the product encoded by B. cenocepacia H111 bepA-L gene cluster was identified as the water-insoluble exopolysaccharide, using mutant strains and NMR spectroscopy of the purified polysaccharides. It was also demonstrated that the B. cenocepacia H111 wild type strain produces the water-insoluble exopolysaccharide in pellicles, thus underlining its potential importance in in vivo infections.

Automated summary

Burkholderia cenocepacia is an opportunistic pathogen that causes in-fections in cystic fibrosis patients. Biofilm and its associated exopolysaccharides play a crucial role in infection persistence and antibiotic tolerance. This study identified the water-insoluble exopolysaccharide encoded by the B. cenocepacia H111 bepA-L gene cluster and highlighted its potential importance in in vivo infections.