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Oxygen gradients reshape cross-feeding through emergent spatial organization of gut commensal bacteria www.biorxiv.org/content/10.6... Use of isotope labels and cryo-CLEM-FIB-SIMS to study microbial communities by Hannah Ochner. Collaboration with @kiranrpatil.bsky.social @jmghigolab.bsky.social

Congratulations to @lapassmore.bsky.social, Joint Head of the LMB’s Structural Studies Division, who has been elected an international member of @nationalacademies.org Congratulations to #LMBalumni Andrea Brand who has also been elected. Read more: mrclmb.ac.uk/news-events/... #LMBNews

Congratulations to Manu Hegde, Group Leader & Joint Head of @cellbiol-mrclmb.bsky.social, who has been elected a member of the American Academy of Arts & Sciences. Congratulations also to the #LMBalumni joining him, Julie Ahringer & Edward Egelman. Read more: mrclmb.ac.uk/news-events/... #LMBNews

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 environmental heterogeneity on metabolism and ecology. Here, we investigate how the physical environment modulates the interaction between the gut commensal Bacteroides thetaiotaomicron and Escherichia coli . In anoxic liquid culture, cell-resolved isotope imaging and genetic perturbations reveal exploitative cross-feeding, where E. coli consumes diffusible sugars released by B . thetaiotaomicron during starch degradation. When exposed to intestinal-like oxygen gradients in microfluidics, the interaction is restructured by spatial organization. The species self-organize into complementary niches: E. coli locally depletes sugars and oxygen, thereby expanding the anoxic niche required by B. thetaiotaomicron . A reactive transport model confirms that this organization arises from coupled feedback between physical transport and metabolic reaction rates. Together, our results reveal how physical structure and chemical gradients convert an exploitative cross-feeding interaction into a dynamic niche-construction process that generates emergent spatial organization and stabilizes coexistence. ### Competing Interest Statement The authors have declared no competing interest.