Dual functions:A coumarin–chalcone conjugate inhibits cyclic-di-GMP and quorum-sensing signaling to reduce biofilm formation and virulence of pathogens

Antibiotic resistance or tolerance of pathogens is one of the most serious global public health threats.Bacteria in biofilms show extreme tolerance to almost all antibiotic classes.Thus,use of antibiofilm drugs without bacterial-killing effects is one of the strategies to combat antibiotic tolerance.In this study,we discovered a coumarin–chalcone conjugate C9,which can inhibit the biofilm formation of three common pathogens that cause nosocomial infections,namely,Pseudomonas aeruginosa,Staph-ylococcus aureus,and Escherichia coli,with the best antibiofilm activity against P.aeruginosa.Further investigations indicate that C9 decreases the synthesis of the key biofilm matrix exopolysaccharide Psl and bacterial second messenger cyclic-di-GMP.Meanwhile,C9 can interfere with the regulation of the quorum sensing(QS)system to reduce the virulence of P.aeruginosa.C9 treatment enhances the sensitivity of biofilm to several antibiotics and reduces the survival rate of P.aeruginosa under starvation or oxidative stress conditions,indicating its excellent potential for use as an antibiofilm-forming and anti-QS drug.

Cell division factor ZapE regulates Pseudomonas aeruginosa biofilm formation by impacting the pqs quorum sensing system

Pseudomonas aeruginosa is one of the leading nosocomial pathogens that causes both severe acute and chronic infections.The strong capacity of P.aeruginosa to form biofilms can dramatically increase its antibiotic resistance and lead to treatment failure.The biofilm resident bacterial cells display distinct gene expression profiles and phenotypes compared to their free-living counterparts.Elucidating the genetic determinants of biofilm formation is crucial for the development of antibiofilm drugs.In this study,a highthroughput transposon-insertion site sequencing(Tn-seq)approach was employed to identify novel P.aeruginosa biofilm genetic determinants.When analyzing the novel biofilm regulatory genes,we found that the cell division factor ZapE(PA4438)controls the P.aeruginosa pqs quorum sensing system.The ΔzapE mutant lost fitness against the wild-type PAO1 strain in biofilms and its production of 2-heptyl-3-hydroxy-4(1H)-quinolone(PQS)had been reduced.Further biochemical analysis showed that ZapE interacts with PqsH,which encodes the synthase that converts 2-heptyl-4-quinolone(HHQ)to PQS.In addition,site-directed mutagenesis of the ATPase active site of ZapE(K72A)abolished the positive regulation of ZapE on PQS signaling.As ZapE is highly conserved among the Pseudomonas group,our study suggests that it is a potential drug target for the control of Pseudomonas infections.