title: Impact of flow on ligand-mediated bacterial flocculation.
abstract: To understand the adhesion-fragmentation dynamics of bacterial aggregates (i.e., flocs), we model the aggregates as two ligand-covered rigid spheres. We develop and investigate a model for the attachment/detachment dynamics in a fluid subject to a homogeneous planar shear-flow. The binding ligands on the surface of the flocs experience attractive and repulsive surface forces in an ionic medium and exhibit finite resistance to rotation (via bond tilting). For certain range of material and fluid parameters, our results predict a nonlinear or hysteretic relationship between the binding/unbinding of the floc surface and the net floc velocity (translational plus rotational velocity). We show that the surface adhesion is promoted by increased fluid flow until a critical value, beyond which the bonds starts to yield. Moreover, adhesion is not promoted in a medium with low ionic strength, or flocs with bigger size or higher binder stiffness. The numerical simulations of floc-aggregate number density studies support these findings.
authors.affiliation: Department of Applied Mathematics, University of Colorado, Boulder, CO 80309, United States.
authors.forename: Sarthok
authors.initials: S
authors.lastname: Sircar
authors.forename: David M
authors.initials: DM
authors.lastname: Bortz
mesh_terms: D001422:Bacterial Adhesion / Q000502:physiology*; D018407:Bacterial Physiological Phenomena; D019295:Computational Biology; D004548:Elasticity; D005427:Flocculation; D057446:Hydrodynamics; D007700:Kinetics; D008024:Ligands; D055641:Mathematical Concepts; D008954:Models, Biological; D017711:Nonlinear Dynamics
chemical_list: D008024:Ligands
keywords: Adhesion; Binding kinetics; Bistability; Flocculation; Micro hydrodynamics; Smoluchowski coagulation equations
references.citation: Biophys J. 1985 Jul;48(1):175-83
references.pmid: 4016207
references.citation: Biophys J. 2001 Aug;81(2):799-813
references.pmid: 11463626
references.citation: Small. 2009 Feb;5(2):154-68
references.pmid: 19153991
references.citation: J Biol Chem. 1997 Jul 11;272(28):17880-6
references.pmid: 9211945
references.citation: Biophys J. 1996 Nov;71(5):2902-7
references.pmid: 8913627
references.citation: J Biomech. 2000 Jan;33(1):23-33
references.pmid: 10609515
references.citation: Phys Rev Lett. 2012 Jun 1;108(22):226104
references.pmid: 23003628
references.citation: Biophys J. 2006 Sep 1;91(5):1675-87
references.pmid: 16751237
references.citation: Proc R Soc Lond B Biol Sci. 1988 Jun 22;234(1274):55-83
references.pmid: 2901109
references.citation: J Biol Dyn. 2015;9 Suppl 1:79-89
references.pmid: 25159830
references.citation: J Biomech Eng. 1999 Dec;121(6):636-43
references.pmid: 10633265
references.citation: Biophys J. 2011 Sep 7;101(5):1032-40
references.pmid: 21889439
references.citation: PLoS One. 2012;7(11):e43273
references.pmid: 23152746
references.citation: PLoS One. 2008 Apr 23;3(4):e2016
references.pmid: 18431497
references.citation: Bull Math Biol. 2008 Apr;70(3):745-68
references.pmid: 18071828
references.citation: Proc Natl Acad Sci U S A. 1998 Jul 21;95(15):8922-6
references.pmid: 9671780
references.citation: J Phys Chem A. 2008 Aug 7;112(31):7137-51
references.pmid: 18636700
references.citation: Science. 1978 May 12;200(4342):618-27
references.pmid: 347575
references.citation: J Colloid Interface Sci. 2008 Oct 1;326(1):18-27
references.pmid: 18675985
references.citation: J R Soc Interface. 2007 Aug 22;4(15):721-5
references.pmid: 17327201