Interactions Between Bacterivorous Nematodes and Bacteria Reduce NO Emissions

Trophic interactions in micro-food webs, such as those between nematodes and their bacterial prey, affect nitrogen cycling in soils, potentially changing nitrous oxide (NO) production and consumption. However, how nematode-mediated changes in soil bacterial community composition affect soil NO emissions is largely unknown. Here, microcosm experiments are performed with the bacterial feeding nematode Protorhabditis to explore the potential of nematodes in regulating microbial communities and thereby soil NO emissions. Removal of nematodes by defaunation resulted in increased NO emissions, with the removal of Protorhabditis contributing most to this increase. Further, inoculation with Protorhabditis altered bacterial community composition and increased the relative abundance of Bacillus, and the abundance of the nosZ gene in soil. In vitro experiments indicated that Protorhabditis reinforce the reduction in NO emissions by Bacillus due to suppressing competitors and producing bacteria growth stimulating substances such as betaine. The results indicate that interactions between nematodes and bacteria modify NO emissions providing the perspective for the mitigation of greenhouse gas emissions via manipulating trophic interactions in soil.