title: Elevated levels of the second messenger c-di-GMP contribute to antimicrobial resistance of Pseudomonas aeruginosa.
abstract: Biofilms are highly structured, surface-associated communities. A hallmark of biofilms is their extraordinary resistance to antimicrobial agents that is activated during early biofilm development of Pseudomonas aeruginosa and requires the regulatory hybrid SagS and BrlR, a member of the MerR family of multidrug efflux pump activators. However, little is known about the mechanism by which SagS contributes to BrlR activation or drug resistance. Here, we demonstrate that ΔsagS biofilm cells harbour the secondary messenger c-di-GMP at reduced levels similar to those observed in wild-type cells grown planktonically rather than as biofilms. Restoring c-di-GMP levels to wild-type biofilm-like levels restored brlR expression, DNA binding by BrlR, and recalcitrance to killing by antimicrobial agents of ΔsagS biofilm cells. We likewise found that increasing c-di-GMP levels present in planktonic cells to biofilm-like levels (≥ 55 pmol mg(-1) ) resulted in planktonic cells being significantly more resistant to antimicrobial agents, with increased resistance correlating with increased brlR, mexA, and mexE expression and BrlR production. In contrast, reducing cellular c-di-GMP levels of biofilm cells to ≤ 40 pmol mg(-1) correlated with increased susceptibility and reduced brlR expression. Our findings suggest that a signalling pathway involving a specific c-di-GMP pool regulated by SagS contributes to the resistance of P. aeruginosa biofilms.
authors.affiliation: Department of Biological Sciences, Binghamton University, Binghamton, NY, 13902, USA.
authors.forename: Kajal
authors.initials: K
authors.lastname: Gupta
authors.forename: Julie
authors.initials: J
authors.lastname: Liao
authors.forename: Olga E
authors.initials: OE
authors.lastname: Petrova
authors.forename: K E
authors.initials: KE
authors.lastname: Cherny
authors.forename: Karin
authors.initials: K
authors.lastname: Sauer
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism; D024881:Drug Resistance, Bacterial; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D050296:Microbial Viability / Q000187:drug effects; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D015290:Second Messenger Systems
chemical_list: D000890:Anti-Infective Agents; D001426:Bacterial Proteins; C062025:bis(3',5')-cyclic diguanylic acid; D006152:Cyclic GMP