Quantifying the Contribution of Cryptic Sulfide-Driven Autotrophic Denitrification to N2O Production in a Seasonally
Shuo Wang1,2, Shengjie Li3, He Lyu1
1Institute of Environmental Planning and Management, Institute of Carbon Neutrality, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
Abstract:
Sulfur-autotrophic denitrification (S-ADN) has been frequently reported in inland waters, yet its quantitative contribution to nitrous oxide (N2O) productions remains poorly constrained. By combining field sampling, enrichment cultures, stable isotopes, and metagenomic analysis, we quantified S-ADN-derived N2O productions in an oligotrophic river-reservoir system and validated the universality of our approach across diverse aquatic ecosystems. A Thiobacillus-dominated S-ADN enrichment culture was successfully established over 218 days of continuous supplementation with reduced sulfur compounds, yielding critical isotopic signatures for source partitioning (δ15NBulk, average N isotopic composition; δ18O; and δ15NSP, site preference). Then, the multi-isotope Bayesian model revealed that S-ADN (14.8%) and nitrifier denitrification (NDN, 21.1%) rapidly occupied the ecological niche of heterotrophic denitrification (HDN, 8.6%) to total microbial N2O sources under organic carbon-limited conditions. The cryptic sulfur cycle supplies a considerable pool of electron donors for S-ADN under low-sulfide conditions. Autotrophic denitrifiers (e.g., Thiobacillus, Sulfuritalea) exhibited significant synergistic interactions with ammonia-oxidizing archaea (AOA, Nitrosarchaeum), while ammonia-oxidizing bacteria (AOB, Nitrosomonas) and nitrite-oxidizing bacteria (NOB, Nitrospira) jointly completed nitrification─with Nitrosomonas further competing for nitrite to drive NDN. This study advances the quantitative assessment of S-ADN's role in N2O production and provides novel insights into microbial community interactions in oligotrophic aquatic systems.
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