design: An Illumina amplicon library was obtained according to the 16S rRNA gene Metagenomic Sequencing Library Preparation Illumina protocol (Part #15044223 Rev. A). This targeted the 16S rRNA gene V3 and V4 hypervariable regions, resulting in an amplicon of 460 bp. Amplicons were sequenced using the 2x300 bp paired-ends protocol on a MiSeq Sequencer (Illumina, San Diego, California, US), following the manufacturers instructions.