design: bacterial libraries were prepared via polymerase chain reaction (PCR) amplification using with a primer set (27F, 5- AGRGTTYGATYMTGGCTCAG-3; 1492R, 5-GGTTACCTTGTTACGACTT-3) targeting the full-length 16S rRNA gene. PCR conditions were as follows: initial denaturation at 94 C for 3 min, followed by 25 cycles of denaturation at 95 C for 30 s, then annealing at 55 C for 30 s, then extension at 72 C for 30 s, and a final extension at 72 C for 5 min. The generated PCR products were purified using AMPure beads (Agencourt Bioscience, USA), and the quantity and size of the purified PCR products were verified using the Quant-IT PicoGreen Assay Kit (Invitrogen, UK). The size distribution of the template was assessed using the Agilent DNA 12000 Kit (Agilent Technologies, USA). Pooled PCR products for library preparation were processed for PacBio Sequel sequencing using the PacBio DNA Template Prep Kit 1.0 (Pacific Biosciences, USA). The single-molecule real-time (SMRT) sequencing libraries were prepared using the PacBio DNA Sequencing Kit 4.0 and eight SMRT cells (Pacific Biosciences, USA).