Microbial mechanism of sulfide inhibiting N2O reduction during denitrification in fluvo-aquic soil

Abstract:

[Background] The products of denitrification are N2O and N2, thus it causes nitrogen loss and increases greenhouse effect. Sulfide has a significant inhibitory effect on N2O reduction, however, the effect of sulfide on denitrifying bacteria and functional genes of denitrification are unclear. [Objective] To study the effect of sulfide on the accumulation of intermediate products of denitrification (NO and N2O), transcription of functional gene of denitrification (narG, nirS, nirK and nosZ) as well as the structure of the microbial community structure in soil amended with or without carbon source. [Methods] Different levels of sodium sulfide (0 and 150 mg-S/kg-soil) combined different levels of glucose (0 and 1 000 mg-C/kg-soil) were set up in soil microcosms experiment. Robotized incubation system was used to monitor the amount of NO, N2O and N2 accumulated during the incubation, and quantitative reverse transcription PCR (RT-qPCR) was used to quantify the transcriptions of functional gene of denitrification (narG, nirS, nirK and nosZ) as well as the MiSeq technology platform based on 16S rRNA gene high-throughput sequencing was used to analyze microbial community structure. [Results] The addition of sodium sulfide significant inhibited the reduction of N2O, but it had no significant effect on the accumulated N2O. And the addition of sodium sulfide significantly reduced the accumulated NO. Sodium sulfide addition significantly inhibited the activity of N2O reductase at a transcription level in a short time. Sodium sulfide addition inhibited the transcription of Azoarcus, Microvirga, Ensifer, Azohydromonas, Bacillus, Skermanella, Shinella, and Chthoniobacte. According to the query results of the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, the addition of sodium sulfide inhibited the growth of N2O reducing denitrifying bacteria that cannot produce N2O. [Conclusion] The increase of soil sulfide caused by compost or other reasons leads to the inhibition of N2O reduction in denitrification process, which is due to the inhibition of nitrous oxide gene transcription and the selection impact of denitrifying bacteria. This study would be helpful to understand the microbial mechanism of the impact of sulfide on nitrogen metabolism.