Reconciliation between operational taxonomic units and species boundaries

Mohamed Mysara, Peter Vandamme, Ruben Props, Frederiek-Maarten Kerckhof, Natalie Leys, Nico Boon, Jeroen Raes, Pieter Monsieurs

Research output: Contribution to journalA1: Web of Science-articlepeer-review


The development of high-throughput sequencing technologies has revolutionised the field of microbial ecology via 16S rRNA gene amplicon sequencing approaches. Clustering those amplicon sequencing reads into operational taxonomic units (OTUs) using a fixed cut-off is a commonly used approach to estimate microbial diversity. A 97% threshold was chosen with the intended purpose that resulting OTUs could be interpreted as a proxy for bacterial species. Our results show that the robustness of such a generalised cut-off is questionable when applied to short amplicons only covering one or two variable regions of the 16S rRNA gene. It will lead to biases in diversity metrics and makes it hard to compare results obtained with amplicons derived with different primer sets. The method introduced within this work takes into account the differential evolutional rates of taxonomic lineages in order to define a dynamic and taxonomic-dependent OTU clustering cut-off score. For a taxonomic family consisting of species showing high evolutionary conservation in the amplified variable regions, the cut-off will be more stringent than 97%. By taking into consideration the amplified variable regions and the taxonomic family when defining this cut-off, such a threshold will lead to more robust results and closer correspondence between OTUs and species. This approach has been implemented in a publicly available software package called DynamiC.

Original languageEnglish
JournalFEMS Microbiology Ecology
Issue number4
Publication statusPublished - 1-Apr-2017
Externally publishedYes


  • Biological Evolution
  • Classification
  • Cluster Analysis
  • DNA Primers
  • Genetic Variation
  • High-Throughput Nucleotide Sequencing
  • RNA, Ribosomal, 16S/genetics


Dive into the research topics of 'Reconciliation between operational taxonomic units and species boundaries'. Together they form a unique fingerprint.

Cite this