title: Quorum-sensing and cheating in bacterial biofilms.
abstract: The idea from human societies that self-interest can lead to a breakdown of cooperation at the group level is sometimes termed the public goods dilemma. We tested this idea in the opportunistic bacterial pathogen, Pseudomonas aeruginosa, by examining the influence of putative cheats that do not cooperate via cell-to-cell signalling (quorum-sensing, QS). We found that: (i) QS cheating occurs in biofilm populations owing to exploitation of QS-regulated public goods; (ii) the thickness and density of biofilms was reduced by the presence of non-cooperative cheats; (iii) population growth was reduced by the presence of cheats, and this reduction was greater in biofilms than in planktonic populations; (iv) the susceptibility of biofilms to antibiotics was increased by the presence of cheats; and (v) coercing cooperator cells to increase their level of cooperation decreases the extent to which the presence of cheats reduces population productivity. Our results provide clear support that conflict over public goods reduces population fitness in bacterial biofilms, and that this effect is greater than in planktonic populations. Finally, we discuss the clinical implications that arise from altering the susceptibility to antibiotics.
authors.affiliation: School of Molecular Medical Sciences, Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK. steve.diggle@nottingham.ac.uk
authors.forename: Roman
authors.initials: R
authors.lastname: Popat
authors.forename: Shanika A
authors.initials: SA
authors.lastname: Crusz
authors.forename: Marco
authors.initials: M
authors.lastname: Messina
authors.forename: Paul
authors.initials: P
authors.lastname: Williams
authors.forename: Stuart A
authors.initials: SA
authors.lastname: West
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Diggle
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development*; D024881:Drug Resistance, Bacterial; D009154:Mutation; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D053038:Quorum Sensing; D015534:Trans-Activators / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; C080365:LasR protein, Pseudomonas aeruginosa; D015534:Trans-Activators