title: Extracellular DNA shields against aminoglycosides in Pseudomonas aeruginosa biofilms.
abstract: Within recent years, it has been established that extracellular DNA is a key constituent of the matrix of microbial biofilms. In addition, it has recently been demonstrated that DNA binds positively charged antimicrobials such as aminoglycosides and antimicrobial peptides. In the present study, we provide evidence that extracellular DNA shields against aminoglycosides in Pseudomonas aeruginosa biofilms. We show that exogenously supplemented DNA integrates into P. aeruginosa biofilms and increases their tolerance toward aminoglycosides. We provide evidence that biofilms formed by a DNA release-deficient P. aeruginosa quorum-sensing mutant are more susceptible to aminoglycoside treatment than wild-type biofilms but become rescued from the detrimental action of aminoglycosides upon supplementation with exogenous DNA. Furthermore, we demonstrate that exposure to lysed polymorphonuclear leukocytes, which are thought to be a source of extracellular DNA at sites of infections, increases the tolerance of P. aeruginosa biofilms toward aminoglycosides. Although biofilm-associated aminoglycoside tolerance recently has been linked to extracellular DNA-mediated activation of the pmr genes, we demonstrate that the aminoglycoside tolerance mediated by the presence of extracellular DNA is not caused by activation of the pmr genes in our P. aeruginosa biofilms but rather by a protective shield effect of the extracellular DNA.
authors.affiliation: Department of International Health, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Wen-Chi
authors.initials: WC
authors.lastname: Chiang
authors.forename: Martin
authors.initials: M
authors.lastname: Nilsson
authors.forename: Peter Østrup
authors.initials: PØ
authors.lastname: Jensen
authors.forename: Niels
authors.initials: N
authors.lastname: Høiby
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Nielsen
authors.forename: Michael
authors.initials: M
authors.lastname: Givskov
authors.forename: Tim
authors.initials: T
authors.lastname: Tolker-Nielsen
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000617:Aminoglycosides / Q000096:biosynthesis / Q000378:metabolism* / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D018441:Biofilms / Q000187:drug effects; D004247:DNA / Q000378:metabolism* / Q000494:pharmacology; D004269:DNA, Bacterial / Q000378:metabolism* / Q000494:pharmacology; D005110:Extracellular Space / Q000737:chemistry*; D006801:Humans; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009504:Neutrophils / Q000737:chemistry; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D053038:Quorum Sensing; D015534:Trans-Activators / Q000172:deficiency / Q000235:genetics
chemical_list: D018528:ATP-Binding Cassette Transporters; D000617:Aminoglycosides; D001426:Bacterial Proteins; D004269:DNA, Bacterial; C080365:LasR protein, Pseudomonas aeruginosa; C086515:RhlR protein, Pseudomonas aeruginosa; D015534:Trans-Activators; D004247:DNA