Collective motion of bacteria in two dimensions

Abstract

Collective motion can be observed in biological systems over a wide range of length scales, from large animals to bacteria. Collective motion is thought to confer an advantage for defense and adaptation. A central question in the study of biological collective motion is how the traits of individuals give rise to the emergent behavior at population level. This question is relevant to the dynamics of general self-propelled particle systems, biological self-organization, and active fluids. Bacteria provide a tractable system to address this question, because bacteria are simple and their behavior is relatively easy to control. In this mini review we will focus on a special form of bacterial collective motion, i.e., bacterial swarming in two dimensions. We will introduce some organization principles known in bacterial swarming and discuss potential means of controlling its dynamics. The simplicity and controllability of 2D bacterial behavior during swarming would allow experimental examination of theory predictions on general collective motion.Keywords: bacterial swarming; biofilm; flagellar motility; gliding motility; biological self-organization; emergent behavior INTRODUCTION Collective motion is the coordinated self-organized movement of many individuals arising from physical, chemical, or social interactions between these individuals [1]. Collective motion is ubiquitous in nature. Familiar examples include fish schooling [2], bird flocking [3,4], and insect swarming [5]. At microscale, animal cells and microorganisms also display collective motion, such as cancer invasion and tissue development [6], phytoplankton (algae) blooms in surface waters [7], amoebae aggregation under starvation [8], and bacterial swarming during the formation of biofilms and fruiting bodies [9,10]. Collective motion is thought to confer an advantage for defending predators [2,3] and for adapting to the environment [9,10].Despite the vast differences in length scale and propulsion mechanism, collective motion across biological systems shares a similar feature: global order arises spontaneously from local interactions between individuals that do not have access to global information. Intriguingly, the traits of individuals determine the emergent global order in a non-intuitive manner; change of individuals' traits may lead to dramatically different collective behavior. Therefore, a central aim in the study of biological collective motion is to reveal its organization principles, i.e., how the traits of individuals give rise to the emergent behavior at population level. This question is not only important to biology, but also of great interest to other disciplines, such as physics, engineering, and computer science. For example, biological collective motion provides insights for understanding the physics of self-organization in non-equilibrium systems [1]; organization principles revealed in biological collective motion have inspired the design of aerial robots that can perform autonomous group flights [11], the design of swarming robots ...

Active matter invasion

“…The latter has been identified as the primary mode of cancer cell invasion [1,2]. Similarly collective migration is the prime mode of growth and invasion by bacterial biofilms [3,4,5].…”

Single Nanoparticle Tracking Reveals Efficient Long-Distance Undercurrent Transport above Swarming Bacteria

“…The layer of fluid is only micrometers-thick and even thinner at the swarm edge, and has Reynold number as low as 10 -5 . The swarm fluid can trap surfactants, modify the surface tension of liquids, supports the flagella operation, and carry nutrients or other signaling molecules [9][10][11] . A fundamental challenge is to understand the relationships between bacteria cells and the fluid medium 5,12,13 .…”

Spreading of nonmotile bacteria on a hard agar plate: Comparison between agent-based and stochastic simulations

“…Bacteria in a Petri dish environment exhibit a large variety of complex spatial patterns ranging from compact circular growth, concentric rings to long branched patterns [4][5][6][7][8][9][10][11]. The colony morphology depends upon various factors such as nutrient concentration, cell motility, growth-proliferation and death dynamics, and other chemical and physical variables [12][13][14][15][16][17][18][19][20]. In a classic experiment, Wakita et al [4] obtained the phase-diagram of Bacillus subtilis colony morphology as a function of nutrient concentration and solidity of agar medium and identified five basic morphologies: (A) diffusion limited aggregation (DLA), (B) Eden-like, (C) concentric ring-like, (D) homogeneous spreading, and (E) dense branching morphology (DBM).…”