2.4. Biosampling and 16S rRNA Sequencing
STERILE
Participants were asked to collect a fecal sample at home at baseline and at the six month follow-up visit, in a sterile container (Sarstedt, Nümbrecht, Germany). Upon collection participants immediately stored the fecal sample in their −20 °C freezer until transfer to the research center in a provided icepack. Samples there were kept in a −20 °C freezer until transfer to central storage at −80 °C once a week. Time of sample production, storage at −20 °C, and storage at −80 °C was noted. After all stool samples were collected, they were shipped to the Amsterdam University Medical Center, Amsterdam, the Netherlands on dry ice for DNA extraction. Total genomic DNA was isolated using an adapted repeated bead-beating method [