Edgar RC.

Bioinformatics. 2018 Jul 15;34(14):2371-2375. doi:10.1093/bioinformatics/bty113

Updating the 97% identity threshold for 16S ribosomal RNA OTUs.

Following a benchmark on V4 regions of the 16S rRNA, proposes to raise the threshold to 99% or to just use sequence variants (also called ZOTUS, Zero-radius OTUs. Identity computed as the number of columns containing identical letters divided by the number of columns containing at least one letter.