A global genomic survey of infant gut bifidobacteria shows that B. infantis remains highly prevalent and diverse in infants from low- and middle-income countries but scarce in Western, industrialized populations and poorly represented in current probiotics. This genomic and culture collection catalogs geo-specific B. infantis strains and provides a blueprint for developing probiotics tailored to local diets and populations to support infant health.

Nature, Published online: 11 March 2026; doi:10.1038/s41586-026-10136-zThe acquisition of a parasitic anti-phage mobile genetic element, PLE11, showing potent anti-phage activity against cocirculating ICP1, and the subsequent evolution of ICP1 to escape this defense, are captured, revealing the molecular basis of the natural selection of a globally notable pathogen and its virus.