environmental metagenome
The initial concentration of DNA was evaluated using the Qubit dsDNA HS Assay Kit (Life Technologies). Libraries were prepared using Illumina DNA Prep, (M) Tagmentation library preparation kit (Illumina) following the manufacturer's user guide. For the samples with enough DNA, 50 ng DNA was used, and for the samples 11A and EB that showed not enough or too low DNA, all available (22uL) DNA was used to prepare the libraries. The samples underwent the simultaneous fragmentation and addition of adapter sequences. These adapters are utilized during a limited-cycle PCR in which unique indices were added to the sample. Following the library preparation, the final concentration of the libraries (Table 1) was measured using the Qubit dsDNA HS Assay Kit (Life Technologies), and the average library size (Table 1) was determined using the Agilent 2100 Bioanalyzer (Agilent Technologies). The libraries were then pooled in equimolar ratios of 0.6nM, and for the sample EB that showed low DNA concentration (0.15ng/uL) of the final library, equal volume of the library as for other samples was pooled. The libraries were then sequenced paired end for 300 cycles using the NovaSeq 6000 system (Illumina).