Lectin-Like Bacteriocins from Pseudomonas spp. Utilise D-Rhamnose Containing Lipopolysaccharide as a Cellular Receptor

Abstract

Lectin-like bacteriocins consist of tandem monocot mannose-binding domains and display a genus-specific killing activity. Here we show that pyocin L1, a novel member of this family from Pseudomonas aeruginosa, targets susceptible strains of this species through recognition of the common polysaccharide antigen (CPA) of P. aeruginosa lipopolysaccharide that is predominantly a homopolymer of d-rhamnose. Structural and biophysical analyses show that recognition of CPA occurs through the C-terminal carbohydrate-binding domain of pyocin L1 and that this interaction is a prerequisite for bactericidal activity. Further to this, we show that the previously described lectin-like bacteriocin putidacin L1 shows a similar carbohydrate-binding specificity, indicating that oligosaccharides containing d-rhamnose and not d-mannose, as was previously thought, are the physiologically relevant ligands for this group of bacteriocins. The widespread inclusion of d-rhamnose in the lipopolysaccharide of members of the genus Pseudomonas explains the unusual genus-specific activity of the lectin-like bacteriocins.

Single-Nucleotide Polymorphisms Found in the migA and wbpX Glycosyltransferase Genes Account for the Intrinsic Lipopolysaccharide Defects Exhibited by Pseudomonas aeruginosa PA14

“…CPA was found to be a receptor for bacteriophage A7 (27) and for lectin-like bacteriocins (28). Lectin-like bacteriocins, such as pyocin L1 and putidacin L1, display a genus-specific killing activity.…”

“…Lectin-like bacteriocins, such as pyocin L1 and putidacin L1, display a genus-specific killing activity. McCaughey et al (28) reported that recognition of CPA occurs through binding of D-Rha at the conserved QxDxNxVxY sugar binding motifs of the C-terminal lectin domain and that this interaction is a prerequisite for bactericidal activity. The lack of CPA in PA14 should make it resistant to killing by these bacteriocins and provide an advantage during competition against other P. aeruginosa bacteria in a mixed bacterial community environment.…”

“…The importance of the latter operon to CPA biosynthesis has been established based on evidence collected from mutagenesis and overexpression experiments (25). CPA was found to play important biological roles as a receptor for bacteriophage A7 (27) and lectin-like bacteriocins (28) and as a surface antigen for P. aeruginosa that is important for adherence to human bronchial epithelial cells (29). In a recent study, Murphy et al (30) showed that CPA is required for strain PAO1 to develop mature and robust biofilms.…”

The therapeutic potential of bacteriocins as protein antibiotics

“…Although less well understood, the Tol system is also required for the entry of some CLBs. Several CLBs, such as colicin N and pyocin L1, have also been shown to interact with lipopolysaccharides (LPSs) on the cell surface [37,38]. The cytotoxic domains of CLBs are commonly pore-forming ionophores or nucleases, but some also have lipid II-or peptidoglycan-degrading activity ( Figure 1) [39].…”

Determining Microbial Products and Identifying Molecular Targets in the Human Microbiome

“…Consequently, microbes produce many products dedicated to preserving ecosystem homeostasis via microbe-microbe interactions. To monitor their own species abundance in the community, microbes produce and detect self-made metabolites in the process of quorum sensing (Bassler and Losick, 2006); they also secrete inhibitory metabolites such as bacteriocins to directly kill or inhibit growth of competing organisms (Cotter et al, 2005; McCaughey et al, 2014). Currently-characterized mediators of microbe-microbe interactions fall into two broad classes: within-clade positive signaling, and between-clade antagonism.…”