Oxygen gradients shape cross-feeding, leading to emergent spatial organization in gut commensal bacteria

ABSTRACT: Microbial interactions unfold within environments structured by physical transport, and chemical gradients, yet most mechanistic studies rely on well-mixed systems that mask the reciprocal influences of ecology and metabolism. Here, we dissected the interactions between the mammalian gut commensal Bacteroides thetaiotaomicron, a primary degrader of dietary polysaccharides, and Escherichia coli, a facultative intestinal anaerobe. In anoxic liquid culture, B. thetaiotaomicron extracellularly hydrolyzes amylopectin and releases diffusible breakdown products that E. coli assimilates, as confirmed by C¹³-starch tracing and sugar utilzation-impaired mutants. In a microfluidic system engineered to mimic intestinal crypt-like oxygen gradients, this same pair of species no longer behaves as in bulk culture, but self-organizes into complementary spatial niches. B. thetaiotaomicron colonizes anoxic regions where it degrades polysaccharides, while E. coli occupies oxygenated zones where it consumes the released sugars. Through aerobic respiration, E. coli locally reduces oxygen, widening the anoxic region that B. thetaiotaomicron subsequently invades. Disrupting sugar uptake in E. coli collapses this organization, whereas increasing oxygen availability reverses it. A reaction–transport model shows that these patterns arise from coupled feedbacks between resource release, resource consumption, and oxygen modification. Together, our results reveal how spatial structure and physicochemical gradients convert a cross-feeding interaction into a dynamic niche-construction process that stabilizes coexistence and generates emergent ecological organization.

ORGANISM(S): Escherichia coli Bacteroides thetaiotaomicron

PROVIDER: GSE327132 | GEO | 2026/08/06

REPOSITORIES: GEO