design: Raw DNA extract diluted to 1ng/l in sterile water, and amplicon generation by PCR (primers 341F and 806R) using a Phusion High-Fidelity PCR Master Mix (New England Biolabs). Amplification product quality check by gel electrophoreses and sample pooling in equimolar ratios. Libraries were generated with a NEBNext UltraTM DNA Library Prep Kit followed by sequnecing (2x250bp).