RNA-Seq of tailings
The purified DNA from each sample was subsequently used to construct a sequencing library (~ 300 bp average insert size) with NEBNext Ultra II DNA PCR-free Library Prep Kit (New England Biolabs, Ipswich, MA, USA), and was shotgun-sequenced with MiSeq Reagent Kit v3 on the Illumina HiSeq 2500 platform with PE150 mode (Illumina, San Diego, CA, USA).