Number of OTUs as function of the total number of sequences. A and B: Rarefaction curves of individual samples for the V1V2 (A) and the V6 datasets (B). Curves were generated at 3% genetic difference using MOTHUR v1.17.0 . C and D: Rarefaction curves of the pooled dataset for both V1V2 reads (C) and V6 reads (D). OTUs with ≤3%, ≤6% and ≤10% pairwise sequence difference generated using MOTHUR v1.17.0  are assumed to belong to the same species, genus and family, respectively.
Siddiqui et al. BMC Microbiology 2011 11:244 doi:10.1186/1471-2180-11-244