Environmental metagenome
Total genomic DNA of the microbial community was extracted according to the instructions of the E.Z.N.A. soil DNA kit (Omega Bio-tek, Norcross, GA, U.S.). After DNA extraction, the concentration and purity of the DNA were detected, and the integrity of the DNA was checked using 1% agarose gel electrophoresis. The DNA was fragmented using a Covaris M220 (Genes Company, China) to obtain fragments of approximately 350 bp for the construction of a paired-end (PE) library.