Ecological theory predicts interactions between species to become more positive
under abiotic stress, while competition should prevail in more benign environments. However, experimental tests of this stress gradient hypothesis in natural
microbial communities are lacking. We test this hypothesis by measuring interactions between 10 ...
Ecological theory predicts interactions between species to become more positive
under abiotic stress, while competition should prevail in more benign environments. However, experimental tests of this stress gradient hypothesis in natural
microbial communities are lacking. We test this hypothesis by measuring interactions between 10 different members of a bacterial community inhabiting potting
compost in the presence or absence of toxic copper stress. We found that copper
stress caused significant net changes in species interaction signs, shifting the net
balance towards more positive interactions. This pattern was at least in part driven
by copper-sensitive isolates – that produced relatively small amounts of metaldetoxifying siderophores – benefitting from the presence of other species that produce extracellular detoxifying agents. As well as providing support for the stress
gradient hypothesis, our results highlight the importance of community-wide public goods in shaping microbial community composition