Dependence of the number of OTUs on the alignment method used. The percentages indicate clustering radius.

Trimmed sequences refer to sequences in which elementary hand-curation was performed (see introductory paragraphs of Results for more information). Merged refers to the multiple alignment that is a merging of the hypervariable regions aligned by NAST+SILVA regions with strong secondary structure conservation aligned by RDP+Infernal. See Introduction for more information. Note that crude hand-curation can reduce numbers of OTUs by a whole order of magnitude.