title: High density waves of the bacterium Pseudomonas aeruginosa in propagating swarms result in efficient colonization of surfaces.
abstract: This work describes a new, to our knowledge, strategy of efficient colonization and community development where bacteria substantially alter their physical environment. Many bacteria move in groups, in a mode described as swarming, to colonize surfaces and form biofilms to survive external stresses, including exposure to antibiotics. One such bacterium is Pseudomonas aeruginosa, which is an opportunistic pathogen responsible for both acute and persistent infections in susceptible individuals, as exampled by those for burn victims and people with cystic fibrosis. Pseudomonas aeruginosa often, but not always, forms branched tendril patterns during swarming; this phenomena occurs only when bacteria produce rhamnolipid, which is regulated by population-dependent signaling called quorum sensing. The experimental results of this work show that P. aeruginosa cells propagate as high density waves that move symmetrically as rings within swarms toward the extending tendrils. Biologically justified cell-based multiscale model simulations suggest a mechanism of wave propagation as well as a branched tendril formation at the edge of the population that depends upon competition between the changing viscosity of the bacterial liquid suspension and the liquid film boundary expansion caused by Marangoni forces. Therefore, P. aeruginosa efficiently colonizes surfaces by controlling the physical forces responsible for expansion of thin liquid film and by propagating toward the tendril tips. The model predictions of wave speed and swarm expansion rate as well as cell alignment in tendrils were confirmed experimentally. The study results suggest that P. aeruginosa responds to environmental cues on a very short timescale by actively exploiting local physical phenomena to develop communities and efficiently colonize new surfaces.
authors.affiliation: Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, Notre Dame, Indiana.
authors.forename: Huijing
authors.initials: H
authors.lastname: Du
authors.affiliation: Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, Notre Dame, Indiana.
authors.forename: Zhiliang
authors.initials: Z
authors.lastname: Xu
authors.affiliation: Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, Indiana.
authors.forename: Morgen
authors.initials: M
authors.lastname: Anyan
authors.affiliation: Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, Notre Dame, Indiana.
authors.forename: Oleg
authors.initials: O
authors.lastname: Kim
authors.affiliation: Notre Dame Integrated Imaging Facility, University of Notre Dame, Notre Dame, Indiana; Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana.
authors.forename: W Matthew
authors.initials: WM
authors.lastname: Leevy
authors.affiliation: Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, Indiana; Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana; Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana.
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Shrout
authors.affiliation: Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, Notre Dame, Indiana; Department of Medicine, Indiana University School of Medicine, Indiana. Electronic address: albemark@gmail.com.
authors.forename: Mark
authors.initials: M
authors.lastname: Alber
mesh_terms: D008954:Models, Biological; D011550:Pseudomonas aeruginosa / Q000166:cytology* / Q000254:growth & development*; D062211:Spatio-Temporal Analysis; D013499:Surface Properties