Escherichia coli strain:EcNR1 Raw sequence reads

Here, we explored empirically the likelihood, population dynamics, and genetic mechanisms underpinning evolutionary rescue in an obligate mutualism mediated by reciprocal amino acid exchange in Escherichia coli. We observed that >80% of the communities avoided extinction when exposed to two different types of lethal stresses. Of note, only one of the partners survived in all these cases. Genetic and phenotypic analyses show that the survivor reverted to autonomy by metabolically bypassing the auxotrophy, with little evidence of specific adaptation to the stressors. Crucially, we found that the mutualistic partners were more sensitive to both stresses than prototrophs, so that reversion to autonomy was sufficient to alleviate stress below lethal levels. We observed this increased sensitivity across several other stresses, suggesting that this may be a general property of obligate mutualisms mediated by amino acid exchange. Our results reveal that evolutionary rescue critically depends on the specific genetic and physiological details of the interacting partners, adding rich layers of complexity to the endeavor of predicting microbial community resilience under intense environmental deterioration.