Taurine inhibits the nitrous oxide formation processes in soil through modifying the bacterial community

The raw FASTQ files were de-multiplexed using an in-house perl script, and then quality-filtered by fastp version 0.19.6 (Chen et al. 2018) and merged by FLASH version 1.2.7 (Magoc & Salzberg 2011) Then the optimized sequences were clustered into operational taxonomic units (OTUs) using UPARSE 7.1 (Edgar 2013; Stackebrandt E 1994) with 97% sequence similarity level. The most abundant sequence for each OTU was selected as a representative sequence. The taxonomy of each OTU representative sequence was analyzed by RDP Classifier version 2.2 (Wang et al. 2007) against the 16S rRNA gene database (Silva v138) using the confidence threshold of 0.7. The Chao1, ACE, Shannon, and Simpson indices, and Good's coverage were calculated using QIIME (version 1.7.0) (Caporaso et al. 2010). The metabolic functions of the soil bacterial community were predicted by PICRUSt2 (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) (Douglas et al. 2020) based on OTU representative sequences. The taxonomic groups of soil bacteria at the genus level were identified from the OTU Table based on Knowles (2003) to determine the abundances of the N2 fixing and nitrifying and denitrifying bacteria. The relative abundances of the total N2 fixing, nitrifying and denitrifying bacteria were calculated by summing up the abundances of individual genera.