design: DNA was extracted as described previously [PMID: 25144201]. An automated DNA isolation system (GENE PREP STAR PI-480; KURABO, Tokyo, Japan) was used for this process. The V3-V4 bacterial and archaeal 16S rRNA gene regions were amplified using Pro341F/Pro805R primers and the dual-index method [PMID: 25144201,26068535]. Barcoded amplicons were sequenced by paired-end sequencing with a 2301-bp cycle on a MiSeq system using the MiSeq Reagent Kit version 3 (644 cycle chemistry).