Novel Outlook in Microbial Ecology: Nonmutualistic Interspecies Electron Transfer.

Recent advances in microbial electrochemical technologies have revealed the existence of numerous and highly diverse microorganisms able to exchange electrons with electrodes. This diversity could reflect the capacity of microorganisms to release and/or retrieve electrons with each other in natural environments. So far, this interspecies electron transfer has been studied with a special focus on syntrophy and was successfully demonstrated for several couples of species. In this article we argue that electron exchange between microbes exists beyond syntrophy or mutualism and could also promote competitive and even parasitic behaviour. Based on three interesting case studies identified from the literature, we also highlight that such nonmutualistic interactions could be widespread and of particular significance for the survival of pathogens or the shaping of complex microbial communities.