Antibacterial activity of a lectin-like Burkholderia cenocepacia protein

Bacteriocins of the LlpA family have previously been characterized in the γ-proteobacteria Pseudomonas and Xanthomonas. These proteins are composed of two MMBL (monocot mannose-binding lectin) domains, a module predominantly and abundantly found in lectins from monocot plants. Genes encoding four different types of LlpA-like proteins were identified in genomes from strains belonging to the Burkholderia cepacia complex (Bcc) and the Burkholderia pseudomallei group. A selected recombinant LlpA-like protein from the human isolate Burkholderia cenocepacia AU1054 displayed narrow-spectrum genus-specific antibacterial activity, thus representing the first functionally characterized bacteriocin within this β-proteobacterial genus. Strain-specific killing was confined to other members of the Bcc, with mostly Burkholderia ambifaria strains being susceptible. In addition to killing planktonic cells, this bacteriocin also acted as an antibiofilm agent. Bacteriocins mediate highly selective antagonism among closely related bacteria but such antimicrobial proteins have not yet been reported in Burkholderia. We identified a lectin-like protein of the LlpA family in a Burkholderia cenocepacia human isolate that strain-specifically and selectively kills planktonic and biofilm cells of other Burkholderia cepacia complex members.