The 16S ribosomal RNA content of the cDNA pyrosequencing reads was analyzed by comparison to the ribosomal database of the Ribosomal Database Project (RDP) version 10 (http://rdp.cme. msu.edu/) [34] . The selected output reads were classified by the RDP Classifier tool (Naïve Bayesian rRNA Classifier Version 2.0) using the Taxonomic Outline of the Bacteria and Archaea, release 7.8, for the setup of the taxonomical hierarchy [35] . The output files were analyzed with MEGAN version 3.7.2 [32] . For the MD OCTpool, the combined data of three individual 454 runs was used.