hide
Free keywords:
-
Abstract:
For billions of years, photosynthetic microbes have evolved under the variable
exposure to sunlight in diverse ecosystems and microhabitats all over our
planet. Their abilities to dynamically respond to alterations of the luminous
intensity, including phototaxis, surface association and diurnal cell cycles, are
pivotal for their survival. If these strategies fail in the absence of light, the
microbes can still sustain essential metabolic functionalities and motility by
switching their energy production from photosynthesis to oxygen respiration.
For suspensions of motile C. reinhardtii cells above a critical density, we demonstrate
that this switch reversibly controls collective microbial aggregation.
Aerobic respiration dominates over photosynthesis in conditions of low light,
which causes the microbial motility to sensitively depend on the local availability
of oxygen. For dense microbial populations in self-generated oxygen
gradients, microfluidic experiments and continuum theory based on a reaction–
diffusion mechanism show that oxygen-regulated motility enables the
collective emergence of highly localized regions of high and low cell densities.
