title: Type IV pili interactions promote intercellular association and moderate swarming of Pseudomonas aeruginosa.
abstract: Pseudomonas aeruginosa is a ubiquitous bacterium that survives in many environments, including as an acute and chronic pathogen in humans. Substantial evidence shows that P. aeruginosa behavior is affected by its motility, and appendages known as flagella and type IV pili (TFP) are known to confer such motility. The role these appendages play when not facilitating motility or attachment, however, is unclear. Here we discern a passive intercellular role of TFP during flagellar-mediated swarming of P. aeruginosa that does not require TFP extension or retraction. We studied swarming at the cellular level using a combination of laboratory experiments and computational simulations to explain the resultant patterns of cells imaged from in vitro swarms. Namely, we used a computational model to simulate swarming and to probe for individual cell behavior that cannot currently be otherwise measured. Our simulations showed that TFP of swarming P. aeruginosa should be distributed all over the cell and that TFP-TFP interactions between cells should be a dominant mechanism that promotes cell-cell interaction, limits lone cell movement, and slows swarm expansion. This predicted physical mechanism involving TFP was confirmed in vitro using pairwise mixtures of strains with and without TFP where cells without TFP separate from cells with TFP. While TFP slow swarm expansion, we show in vitro that TFP help alter collective motion to avoid toxic compounds such as the antibiotic carbenicillin. Thus, TFP physically affect P. aeruginosa swarming by actively promoting cell-cell association and directional collective motion within motile groups to aid their survival.
authors.affiliation: Departments of Civil and Environmental Engineering and Earth Sciences.
authors.forename: Morgen E
authors.initials: ME
authors.lastname: Anyan
authors.affiliation: Physics.
authors.forename: Aboutaleb
authors.initials: A
authors.lastname: Amiri
authors.affiliation: Applied and Computational Mathematics and Statistics, and.
authors.forename: Cameron W
authors.initials: CW
authors.lastname: Harvey
authors.affiliation: Applied and Computational Mathematics and Statistics, and Mathematical Institute, Charles University, 18675 Prague, Czech Republic; and.
authors.forename: Giordano
authors.initials: G
authors.lastname: Tierra
authors.affiliation: Departments of Civil and Environmental Engineering and Earth Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN 46556;
authors.forename: Nydia
authors.initials: N
authors.lastname: Morales-Soto
authors.affiliation: Departments of Civil and Environmental Engineering and Earth Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN 46556;
authors.forename: Callan M
authors.initials: CM
authors.lastname: Driscoll
authors.affiliation: Physics, Applied and Computational Mathematics and Statistics, and Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202 Joshua.Shrout@nd.edu malber@nd.edu.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Alber
authors.affiliation: Departments of Civil and Environmental Engineering and Earth Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN 46556; Biological Sciences, and Joshua.Shrout@nd.edu malber@nd.edu.
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Shrout
mesh_terms: D001422:Bacterial Adhesion / Q000502:physiology*; D018441:Biofilms / Q000254:growth & development; D019295:Computational Biology / Q000379:methods; D003198:Computer Simulation; D010861:Fimbriae, Bacterial / Q000378:metabolism*; D005407:Flagella / Q000502:physiology; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D056265:Microbial Interactions / Q000502:physiology*; D018613:Microscopy, Confocal; D008954:Models, Biological; D009068:Movement / Q000502:physiology*; D011550:Pseudomonas aeruginosa / Q000378:metabolism / Q000502:physiology*; D000097573:Red Fluorescent Protein
chemical_list: D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D000097573:Red Fluorescent Protein
keywords: biofilms; collective motion; computational model; predictive simulations; self-organization