When Worlds Collide: Microbial Ecophysiology at the Aerobic/Anaerobic Interface

Abstract:

The aerobic/anaerobic interface is a transition zone, where conditions, from chemical concentrations to pH, vary along the oxycline. It has long been known that microbes flourish at such interfaces, presumably due to the potential energy available from catalyzing reduction-oxidation reactions using chemicals derived from the anaerobic and aerobic milieus. Indeed, some studies suggest that both microbial diversity and activity is greatest in such settings, and evidenced by the 2-10 fold greater cell abundances associated with such transition zones. That said, the nature of microbial activity found in such transition zones, and the precise extent of their activity, is usually poorly constrained. At hydrothermal vents, for example, scientists have found that distinct communities are associated with each microhabitat, yet our recent studies have shown that canonical anaerobic microbes are found to be active in fully aerobic waters, seemingly well beyond the aerobic/anaerobic interface. Moreover, our research has also shown that the activity of microbes at the aerobic/anaerobic interface can -through extracellular electron transfer- directly influence the activity of microbes in canonically reduced or oxidized habitats. Here we will present these results and discuss the implications for our understanding of how aerobic and anaerobic microbial communities are physiologically coupled across the aerobic/anaerobic interface.