Light-Sensing Microbes in Complex Geometries: Surface Adhesion, Gliding Motility and Self-Organization

Life on Earth has evolved under the exposure of sunlight and many microbes are equipped with photoreceptors enabling them to perceive light. The microhabitats of such light-sensing microbes include liquid-infused soil, porous rocks and microdroplets, featuring complex geometric architectures that induce strong spatial and temporal fluctuations of light exposure. In these confined environments the cells frequently encounter and interact with interfaces. We discovered that Chlamydomonas reinhardtii, a soil-dwelling photoactive microorganism and biological model system, can reversibly switch its adhesion to surfaces on and off by light (Kreis et al., Nature Physics, 2018). The adhesiveness is regulated by a blue-light photoreceptor and mediated by their two flagella. Once they are attached to a surface, gliding motility sets in and enables the microbes to maneuver on the surface. Based on cell tracking and statistical analysis, we study the surface adsorption and gliding motility of light-sensing microbes and demonstrate how surface gliding, in conjunction with cell-cell interactions, may control the emergence of microbial self-organization in confinement.