[3] The microorganisms were specifically categorized by operational taxonomic unit (OTU). (sciencedaily.com)
For example, many studies on human microbiota identify species (or operational taxonomic units) and map evolutionary relationships using the 16S ribosomal RNA gene. (nature.com)
Operational taxonomic units (OTUs) that comprised more than 0.5 % of the OTUs in any sample were grouped into the appropriate family and plotted. (microbiomejournal.biomedcentral.com)