Isolated DNA was checked for concentration and quality on a BioTek Synergy HTX plate reader.
Metagenomic libraries were prepared using the Nextera DNA Flex Library Prep Kit (Illumina) per the manufacturer’s instructions with 100 ng of DNA as sample input. The concentration of the libraries was quantified using the Qubit dsDNA HS assay on a Qubit 2.0 fluorometer (Life Technologies). Library size and quality were assessed via the Agilent High Sensitivity D5000 ScreenTape on an Agilent 4200 Tapestation.
Metagenomic libraries were normalized to an equimolar concentration and pooled. The pool was diluted to 1.8 pM, mixed with a 1% PhiX control library and paired-end sequenced (2 × 75 bp) using a NextSeq 500/550 High Output v2 150-cycle Reagent Cartridge on a NextSeq 500 sequencer (Illumina).