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

Motivation The 16S ribosomal RNA (rRNA) gene is widely used to survey microbial communities. Sequences are often clustered into Operational Taxonomic Units (OTUs) as proxies for species. The canonical clustering threshold is 97% identity, which was proposed in 1994 when few 16S rRNA sequences were available, motivating a reassessment on current data. Results Using a large set of high-quality 16S rRNA sequences from finished genomes, I assessed...