Bacteria frequently engage in obligate metabolic mutualisms with other microorganisms. However, it remains generally unclear how the resulting metabolic dependencies affect the ecological niche space accessible to the whole consortium relative to the niche space available to its constituent individuals. Here we address this issue by systematically cultivating metabolically dependent strains of different bacterial species either individually or as pairwise cocultures in a wide range of carbon sources. Our results show that obligate cross-feeding is significantly more likely to expand the metabolic niche space of interacting bacterial populations than to contract it. Moreover, niche expansion occurred predominantly between two specialist taxa and correlated positively with the phylogenetic distance between interaction partners. Together, our results demonstrate that obligate cross-feeding can significantly expand the ecological niche space of interacting bacterial genotypes, thus explaining the widespread occurrence of this type of ecological interaction in natural microbiomes.

细菌经常与其他微生物进行专性代谢共生。然而，相对于其组成个体可用的生态位空间，由此产生的代谢依赖性如何影响整个联合体可访问的生态位空间通常仍不清楚。在这里，我们通过在广泛的碳源中单独或成对共培养系统地培养不同细菌物种的代谢依赖菌株来解决这个问题。我们的结果表明，专性交叉喂养更有可能扩大相互作用的细菌种群的代谢生态位空间，而不是收缩它。此外，生态位扩张主要发生在两个专业类群之间，并且与相互作用伙伴之间的系统发育距离呈正相关。一起，