DNA was extracted with the DNeasy PowerSoil Pro Kit (Qiagen, Venlo, the Netherlands) following the manufacturers instructions. Upon the addition of lysis buffer, the samples were incubated at 65 C for 10 minutes and subsequently the cells were lyzed by bead beating in a tissue disruptor (Qiagen, Venlo, the Netherlands) at 50 Hz for 10 minutes. Extracted DNA was sent for sequencing of the V3-V4 16S rRNA region (Illumina MiSeq platform, Macrogen, Seoul, South Korea) with the primers Bac341F (CCTACGGGNGGCWGCAG; (Herlemann et al., 2011)) and Bac806R (GGACTACHVGGGTWTCTAAT; (Caporaso et al., 2012) for bacteria and Arch349F (5?-GYGCASCAGKCGMGAAW-3?) and Arch806R (5?-GGACTACVSGGGTATCTAAT-3?) for archaea (Takai & Horikoshi, 2000).