Escherichia coli + Bifidobacterium bifidum Infant-gut Mutualistic Co-culture

Two-member infant-gut co-culture of Escherichia coli and Bifidobacterium bifidum. In healthy, term-born, breastfed infants these genera co-exist despite differing ecological strategies and share evolutionary adaptations for lactose acquisition. In vitro co-culture demonstrates a mutualistic cross-feeding interaction in which E. coli supplies cysteine to its auxotrophic partner B. bifidum, facilitating cooperative degradation of 2'-fucosyllactose (the predominant human milk oligosaccharide), and the liberated monosaccharides in turn sustain E. coli growth, potentially helping regulate E. coli abundance in the infant gut.