| Summary: | More than 80% of infectious bacteria form biofilm, which is a bacterial cell community surrounded by secreted polysaccharides, proteins and glycolipids. Such bacterial superstructure increases resistance to antimicrobials and host defenses. Thus, to control these biofilm-forming pathogenic bacteria requires antimicrobial agents with novel mechanisms or properties. <i>Pseudomonas aeruginosa</i>, a Gram-negative opportunistic nosocomial pathogen, is a model strain to study biofilm development and correlation between biofilm formation and infection. In this study, a recombinant hemolymph plasma lectin (rHPL<sub>OE</sub>) cloned from Taiwanese <i>Tachypleus tridentatus</i> was expressed in an <i>Escherichia coli</i> system. This rHPL<sub>OE</sub> was shown to have the following properties: (1) Binding to <i>P. aeruginosa</i> PA14 biofilm through a unique molecular interaction with rhamnose-containing moieties on bacteria, leading to reduction of extracellular di-rhamnolipid (a biofilm regulator); (2) decreasing downstream quorum sensing factors, and inhibiting biofilm formation; (3) dispersing the mature biofilm of <i>P. aeruginosa</i> PA14 to improve the efficacies of antibiotics; (4) reducing <i>P. aeruginosa</i> PA14 cytotoxicity to human lung epithelial cells in vitro and (5) inhibiting <i>P. aeruginosa</i> PA14 infection of zebrafish embryos in vivo. Taken together, rHPL<sub>OE</sub> serves as an anti-biofilm agent with a novel mechanism of recognizing rhamnose moieties in lipopolysaccharides, di-rhamnolipid and structural polysaccharides (Psl) in biofilms. Thus rHPL<sub>OE</sub> links glycan-recognition to novel anti-biofilm strategies against pathogenic bacteria.
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