Cryptic Sulfur and Oxygen Cycling Potentially Reduces N 2 O-Driven Greenhouse Warming: Underlying Revision Need of the Nitrogen Cycle.

Increasing global deoxygenation has widely formed oxygen-limited biotopes, altering the metabolic pathways of numerous microbes and causing a large greenhouse effect of nitrous oxide (N 2 O). Although there are many sources of N 2 O, denitrification is the sole sink that removes N 2 O from the biosphere, and the low-level oxygen in waters has been classically thought to be the key factor regulating N 2 O emissions from incomplete denitrification. However, through microcosm incubations with sandy sediment, we demonstrate here for the first time that the stress from oxygenated environments does not suppress, but rather boosts the complete denitrification process when the sulfur cycle is actively ongoing. This study highlights the potential of reducing N 2 O-driven greenhouse warming and fills a gap in pre-cognitions on the nitrogen cycle, which may impact our current understanding of greenhouse gas sinks. Combining molecular techniques and kinetic verification, we reveal that dominant inhibitions in oxygen-limited environments can interestingly undergo triple detoxification by cryptic sulfur and oxygen cycling, which may extensively occur in nature but have been long neglected by researchers. Furthermore, reviewing the present data and observations from natural and artificial ecosystems leads to the necessary revision needs of the global nitrogen cycle.