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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. Examples are the cooperative breakdown of complex nutrients in microbes or the construction of elaborate architectures in social insects, in which the individual profits from the collective actions of her peers. However, organisms can similarly display negative interactions by changing the environment in ways that are detrimental for them, for example by resource depletion or the production of toxic byproducts. Here we find an extreme type of negative interactions, in which Paenibacillus sp. bacteria modify the environmental pH to such a degree that it leads to a rapid extinction of the whole population, a phenomenon that we call ecological suicide. Modification of the pH is more pronounced at higher population densities, and thus ecological suicide is more likely to occur with increasing bacterial density. Correspondingly, promoting bacterial growth can drive populations extinct whereas inhibiting bacterial growth by the addition of harmful substances—such as antibiotics—can rescue them. Moreover, ecological suicide can cause oscillatory dynamics, even in single-species populations. We found ecological suicide in a wide variety of microbes, suggesting that it could have an important role in microbial ecology and evolution.

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We thank L. Higgins for providing us with the collection of bacterial soil isolates. J.D. is supported by a DFG fellowship through the Graduate School of Quantitative Biosciences Munich. We thank all members of the Gore lab for reading and discussing the manuscript. This work was funded by an Allen Distinguished Investigator Award and a NIH R01 grant.

Author information

C.R., J.D. and J.G. designed the research. J.D., C.R. and J.G. carried out the experiments and performed the mathematical analysis. C.R., J.D. and J.G discussed and interpreted the results, and wrote the manuscript.

Competing interests

The authors declare no competing interests.

Correspondence to Christoph Ratzke or Jeff Gore.

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Further reading

Fig. 1: Microbial acidification can cause ecological suicide.
Fig. 2: Ecological suicide can cause oscillations in the population size over time.
Fig. 3: Inhibiting growth of the bacteria can save the population.
Fig. 4: Ecological suicide is a common phenomenon in microbes.