OTU

OTU is an acronym that can refer to more than one concept in science and engineering. In biology and ecology, an Operational Taxonomic Unit is a term used to categorize microorganisms or other organisms based on DNA sequence similarity, serving as a practical proxy for species in environmental sequencing studies.

OTU clustering groups sequences into operational units by similarity, typically using a threshold around 97% for 16S rRNA gene data. Clustering can be done de novo, closed-reference, or open-reference, and the resulting units are used to estimate diversity, community composition, and relative abundance.

The approach has limitations: similarity thresholds are arbitrary, outcomes depend on sequencing quality and target gene, and OTU counts may be inflated by errors. In recent years, amplicon sequence variants (ASVs) produced by denoising algorithms have provided higher-resolution, more reproducible alternatives to OTUs.

In telecommunications, OTU stands for Optical Transport Unit, a framing structure used in the Optical Transport Network to encapsulate payload data and overhead for efficient transmission over fiber. Defined by ITU-T standards, OTUs organize the multiplexing, error detection and correction, and management of data across long-haul links. Common variants such as OTU-1, OTU-2, OTU-4, and OTU-8 correspond to different line rates and payload capacities.