The regulation effect of preventing soil nitrogen loss using microbial quorum sensing inhibitors

The primary forces behind the world's nitrogen (N) cycles are soil microbes. Quorum sensing (QS) signals regulate nitrification and denitrification in pure-cultured N-cycling bacteria. However, whether disrupting QS could prevent soil N losses remains unclear. This study explored the feasibility of applying QS inhibitors (QSIs) as a new strategy to reduce N losses from agricultural soils. The two QSIs, penicillic acid and 4-iodo-N-[(3S)-tetrahydro-2-oxo-3-furanyl]-benzeneacetamide (4-iodo PHL), were more effective in reducing N losses than other regularly used inhibitors, including N-(n-butyl) thiophosphoric triamide and 3,4-dimethylpyrazole phosphate. After 36 days of aerobic incubation, penicillic acid and 4-iodo PHL inhibited nitrification by 39% and 68%, respectively. This is attributed to the fact that 4-iodo PHL decreased the abundance of archaeal and bacterial amoA genes, as well as the relative abundance of Candidatus Nitrocosmicus, Candidatus Nitrososphaera, and Nitrospira, while penicillic acid reduced archaeal amoA abundance and the relative abundance of Nitrosospira and the microbes listed above. Penicillic acid also strongly inhibited denitrification (33%) and nitrous oxide (N2O) emissions (61%) at the peak of N2O production (day 4 of anaerobic incubation) via decreasing narG abundance but increasing nosZ abundance. Furthermore, the effect of QSIs on soil microbial communities was only temporary, and the community structure returned to normal over time. Overall, QSIs have application potential in agriculture to reduce soil N losses and the associated effect on climate change.