Ecological suicide in microbes

The growth and survival of organisms often depend on interactions between them. In many cases, these interactions are positive and caused by a cooperative modification of the environment, such as the cooperative breakdown of complex nutrients in microbes [1]-[3] or the construction of elaborate architectures in social insects [4]. However, organisms can similarly display negative interactions by changing the environment in ways that are detrimental for them, eg by resource depletion or the production of toxic byproducts [5]. Here we find an extreme type of negative interactions, in which bacteria modify the environmental pH to such a degree that it leads to a rapid extinction of the whole population, a phenomenon we call ecological suicide. Modification of the pH is more pronounced at higher population densities, and thus ecological suicide is more likely with increasing bacterial density. Correspondingly, promoting bacterial growth can drive populations extinct whereas inhibiting bacterial growth by the addition of harmful substances - like antibiotics - can rescue them. Moreover, ecological suicide can cause oscillatory dynamics, even in single-species populations. We find ecological suicide in a wide variety of microbes, suggesting that it could play a significant role in microbial ecology and evolution.