title: Mechanically-driven phase separation in a growing bacterial colony.
abstract: Secretion of extracellular polymeric substances (EPSs) by growing bacteria is an integral part of forming biofilm-like structures. In such dense systems, mechanical interactions among the structural components can be expected to significantly contribute to morphological properties. Here, we use a particle-based modeling approach to study the self-organization of nonmotile rod-shaped bacterial cells growing on a solid substrate in the presence of self-produced EPSs. In our simulation, all of the components interact mechanically via repulsive forces, occurring as the bacterial cells grow and divide (via consuming diffusing nutrient) and produce EPSs. Based on our simulation, we show that mechanical interactions control the collective behavior of the system. In particular, we find that the presence of nonadsorbing EPSs can lead to spontaneous aggregation of bacterial cells by a depletion attraction and thereby generates phase separated patterns in the nonequilibrium growing colony. Both repulsive interactions between cell and EPSs and the overall concentration of EPSs are important factors in the self-organization in a nonequilibrium growing colony. Furthermore, we investigate the interplay of mechanics with the nutrient diffusion and consumption by bacterial cells and observe that suppression of branch formation occurs due to EPSs compared with the case where no EPS is produced.
authors: Center for Theoretical Biological Physics, Rice University, Houston, TX 77005;
authors: Pushpita
authors: P
authors: Ghosh
authors: Department of Chemistry, Columbia University, New York, NY 10027;
authors: Jagannath
authors: J
authors: Mondal
authors: Center for Theoretical Biological Physics, Rice University, Houston, TX 77005; School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel; and.
authors: Eshel
authors: E
authors: Ben-Jacob
authors: Center for Theoretical Biological Physics, Rice University, Houston, TX 77005; Department of Bioengineering, Rice University, Houston, TX 77005 herbert.levine@rice.edu.
authors: Herbert
authors: H
authors: Levine
mesh_terms: D001419:Bacteria / Q000254:growth & development*; D018407:Bacterial Physiological Phenomena; D018441:Biofilms; D008954:Models, Biological
keywords: biofilms; depletion interaction; extracellular polymeric substance; mechanical interaction; phase separation