Cooperation and spatial self-organization determine rate and efficiency of particulate organic matter degradation in marine bacteria

Abstract

Significance Microorganisms can cooperate by secreting public goods that benefit local neighbors; however, the conditions that favor cooperative growth in the environment, and the way in which this growth alters microbes’ contribution to ecosystem functions, remain unexplored. Here, we show that cooperation mediates the degradation of polysaccharide particles recalcitrant to hydrolysis in aquatic environments. Combining experiments and models, we define the physiological and environmental parameters that mediate the transition from cooperation to competition. Cooperation emerges through the self-organization of cells into ∼10- to 20-µm clusters that enable uptake of diffusible hydrolysis products. When cooperation is required, the degradation of recalcitrant biopolymers can only take place when degraders exceed a critical cell concentration, underscoring the importance of microbial interactions for ecosystem function.