soil metagenome

We conducted an extensive field survey along a 1500 km transect in Inner Mongolia, establishing 101 sampling sites across three distinct steppe types: meadow steppe (MS), typical steppe (TS), and desert steppe (DS). Soil microbial sequencing was performed by Shanghai OE Biotech Co., Ltd. using the Illumina MiSeq platform. Bacterial 16S rRNA genes were amplified with the forward primer 343F (5'-TACGGRAGGCAGCAG-3') and reverse primer 798R (5'-AGGGTATCTAATCCT-3'), using paired-end sequencing with a 250 bp read length. Fungal ITS genes were amplified with the forward primer ITS1F (5'-CTTGGTCATTTAGAGGAAGTAA-3') and reverse primer ITS2 (5'-GCTGCGTTCTTCATCGATGC-3'), also with paired-end sequencing at a 250 bp read length.Soil samples were collected from a 0-10 cm depth to capture the microbial communities within the surface layer of the soil. Raw image data from high-throughput sequencing were processed through base calling to generate raw sequencing reads, typically stored in FASTQ format. Primer sequences were removed using cutadapt software to avoid contamination in subsequent analyses. The quality-filtered paired-end data were then processed using the DADA2 plugin in QIIME2, which included denoising, sequence merging, and chimera removal. This process generated representative sequences and an Amplicon Sequence Variant (ASV) abundance table, referred to as the feature table, ensuring high data accuracy and providing a solid foundation for microbial community analysis.Representative sequences for each ASV were selected using QIIME2 and aligned with reference databases for identification and annotation. 16S rRNA gene sequences were aligned with the Silva database (version 138), while ITS gene sequences were compared to the Unite database. Species identification and annotation were based on ASV units. The Shannon index was employed to assess microbial community diversity.