16S-seq of sludge: inoculum
DNA was extracted by using the FastDNA SPIN Kit for Soil (MP Biomedical, LLC, Ohio, USA). The extracted DNA was purified, amplified, and then sequenced through the NovaSeq6000 platform by Novogene Co., Beijing, China. The primes used for amplifying were 515F (5GTG CCA GCM GCC GCG GTA A3) and 907R (5CCG TCA ATT CCT TTG AGT TT3) and the target region of the primes was the V4-V5 hypervariable region of bacterial 16S rRNA genes.