A Novel Metagenomic Short-Chain Dehydrogenase/Reductase Attenuates Pseudomonas aeruginosa Biofilm Formation and Virulence on Caenorhabditis elegans

In Pseudomonas aeruginosa, the expression of a number of virulence factors, as well as biofilm formation, are controlled by quorum sensing (QS). N-Acylhomoserine lactones (AHLs) are an important class of signaling molecules involved in bacterial QS and in many pathogenic bacteria infection and host colonization are AHL-dependent. The AHL signaling molecules are subject to inactivation mainly by hydrolases (Enzyme Commission class number EC 3) (i.e. N-acyl-homoserine lactonases and N-acyl-homoserine-lactone acylases). Only little is known on quorum quenching mechanisms of oxidoreductases (EC 1). Here we report on the identification and structural characterization of the first NADP-dependent short-chain dehydrogenase/reductase (SDR) involved in inactivation of N-(3-oxo-dodecanoyl)-L-homoserine lactone (3-oxo-C12-HSL) and derived from a metagenome library. The corresponding gene was isolated from a soil metagenome and designated bpiB09. Heterologous expression and crystallographic studies established BpiB09 as an NADP-dependent reductase. Although AHLs are probably not the native substrate of this metagenome-derived enzyme, its expression in P. aeruginosa PAO1 resulted in significantly reduced pyocyanin production, decreased motility, poor biofilm formation and absent paralysis of Caenorhabditis elegans. Furthermore, a genome-wide transcriptome study suggested that the level of lasI and rhlI transcription together with 36 well known QS regulated genes was significantly (≥10-fold) affected in P. aeruginosa strains expressing the bpiB09 gene in pBBR1MCS-5. Thus AHL oxidoreductases could be considered as potent tools for the development of quorum quenching strategies

Inhibition of quorum-sensing: A new paradigm in controlling bacterial virulence and biofilm formation

Bacterial pathogens coordinate the expression of multiple virulence factors and formation of biofilms in cell density dependent manner, through a phenomenon named quorum sensing (QS). Protected in the biofilm community, bacterial cells resist the antibiotic treatment and host immune responses, ultimately resulting in difficult to treat infections. The high incidence of biofilm-related infections is a global concern related with increased morbidity and mortality in healthcare facilities, prolonged time of hospitalization and additional financial cost. This has led to the urgent need for innovative strategies to control bacterial diseases and drug resistance. In this review, we outline the disruption of QS pathways as a novel strategy for attenuation of bacterial virulence and prevention of resistant biofilms formation on medical devices and host tissues. Unlike the traditional antibiotics, inhibiting the QS signaling in bacteria will not kill the pathogen or affect its growth, but will block the targeted genes expression, making the cells less virulent and more vulnerable to host immune response and lower dosage of antimicrobials. We summarize the recent successes and failures in the development of novel anti-QS drugs as well as their application in controlling bacterial infections in healthcare facilities. The inhibitory targeting of the production of QS signals, their transduction and recognition by the other cells in the surrounding are discussed. Special focus is also given to the anti-QS nanomaterials with improved effectiveness and specificity towards the pathogens.Postprint (author's final draft