|PHUOC, TOAN HONG - University Of Trento, Italy|
|COSONATO, STEFANO - University Of Trento, Italy|
|LORY, STEPHEN - Harvard Medical School|
|JOUSSON, OLIVIER - University Of Trento, Italy|
Submitted to: BMC Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2017
Publication Date: 2/7/2017
Citation: Phuoc, T., Carter, M.Q., Cosonato, S., Lory, S., Jousson, O. 2017. Conjugative type IVb pilus recognizes lipopolysaccharide of recipient cells to initiate PAPI-1 pathogenicity island transfer in Pseudomonas aeruginosa. BMC Microbiology. (2017) 17:31 DOI 10.1186/s12866-017-0943-4.
Interpretive Summary: Horizontal gene transfer (HGT) is a major evolutionary mechanism for the acquisition of new phenotypes by microorganisms. HGT allows large scale, rapid evolution and plays an important role in altering the pathogenic potential of bacterial strains due to the transmission of virulence and antibiotic resistance in populations. This study characterized the molecular determinants on the acquisition of a large genomic island containing various genes related to bacterial virulence, biofilm formation, and antibiotic resistance by HGT in the population of P. aeruginoas, an important opportunistic human pathogen. The discovery that A-band lipopolysaccharide (LPS) in recipient cells is required to initiate PAPI-1 transfer provides a putative target for blocking the spread of virulence traits and antibiotic resistance in P. aeruginosa population.
Technical Abstract: Pseudomonas aeruginosa pathogenicity island 1 (PAPI-1) is one of the largest genomic islands of this important opportunistic human pathogen. Previous studies have shown that PAPI-1 encodes several putative virulence factors, a major regulator of biofilm formation, and antibiotic-resistance traits, and that it is horizontally transferable into recipient strains lacking this island. PAPI-1 island is transferred by conjugation mediated by specialized type IV pili encoded by a cluster of ten genes located in PAPI-1. However, the PAPI-1 acquisition mechanism is currently not understood. In this study, we performed a series of conjugation experiments and identified determinants of PAPI-1 acquisition by analyzing transfer efficiency between the donor and a series of mutant recipient strains. Our data shows that A-band lipopolysaccharide (LPS) is required to initiate PAPI-1 transfer, supporting the idea that this structure acts as a receptor for conjugative type IV pilus in recipient strains. These results were verified by PAPI-1 transfer assay experiments supplemented with outer membrane or LPS preparations, and by the binding of pilin fusion protein GST-pilV2’ to immobilized LPS molecules in vitro. We also demonstrated that P. aeruginosa strains that already acquired a copy of PAPI-1 almost completely lost the ability to import additional copies of the island, and that such strains produced much less A-band LPS compared to the strains lacking PAPI-1. This may specify a PAPI-1 exclusion mechanism in P. aeruginosa to avoid uncontrolled expansion of the bacterial genome.