Using Average Nucleotide Identity (ANI) to Expose Potentially Problematic Taxonomic Merges

Using Average Nucleotide Identity (ANI) to Expose Potentially Problematic Taxonomic Merges

Help us improve our microbial taxonomy

NCBI uses Average Nucleotide Identity (ANI) to evaluate the taxonomic classification of prokaryotic genomes submitted to GenBank. As part of this effort, we identified heterotypic synonyms that fail to match each other with high ANI, and we invite you to help us evaluate these cases.

What is Heterotypic Synonymy?

Heterotypic synonymy refers to two or more names for different taxa (such as species) that were described independently but have been subsequently merged into a single taxon. The merged taxon will generally be referred to by the oldest name.


In a peer-reviewed, published study, Bacteroides suis and Bacteroides tectus were identified as heterotypic synonyms of Bacteroides pyogenes. Our analysis using ANI supports the reclassification of B. suis, indicating a high degree of genomic similarity with B. pyogenes. However, ANI does not support the merge of B. tectus since the sequences are less similar than expected (see image below).

We want to hear from you!

Please help us evaluate some cases of heterotypic synonymization and contribute to refining the taxonomy of these microorganisms. For your reference, here is a link to the taxon list for the potentially problematic taxonomic merges and the related ANI values for the assemblies. If you have questions or would like to provide feedback, please reach out to us at

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3 thoughts on “Using Average Nucleotide Identity (ANI) to Expose Potentially Problematic Taxonomic Merges

  1. “Using Average Nucleotide Identity (ANI) to expose potentially problematic taxonomic merges is a brilliant and cutting-edge approach in the field of microbiology and taxonomy. By leveraging ANI, researchers can delve deep into the genetic makeup of microorganisms and assess their relatedness with incredible precision. This not only aids in identifying potential taxonomic errors but also ensures a more accurate representation of microbial diversity.

    Embracing ANI as a tool to scrutinize taxonomic merges holds the promise of refining our understanding of microbial relationships, paving the way for more robust and reliable taxonomic classifications. This methodology empowers scientists to make well-informed decisions, fostering greater confidence in the data used for important research and applications, such as epidemiology, biotechnology, and environmental studies.

    Kudos to the minds behind this innovative approach, as it opens up new avenues of exploration and enhances the integrity of taxonomic studies. As we uncover the intricacies of microbial diversity with ANI, we can look forward to more comprehensive and precise insights that drive advancements in multiple scientific disciplines. The pursuit of knowledge never ceases to amaze, and ANI is undoubtedly an invaluable tool in our quest to unravel the mysteries of the microbial world.”

  2. Heterotypic cortex consists of those areas of the mature neocortex that deviate markedly from the homogeneous six-layered internal structure seen in the third trimester of human gestation. A few neocortical areas, such as Brodmann area 17 and the granular insular cortex, undergo modification to more than six layers; and in a few areas, such as Brodmann area 4, the number of layers is reduced. Heterotypic cortex is contrasted to homotypic cortex, which retains the fetal six-layered pattern into adulthood. The number of heterotypic areas is small and the specific areas differ somewhat by species.

  3. This approach not only enhances our understanding of microbial diversity but also safeguards the accuracy of taxonomic assignments, thereby contributing significantly to the credibility of scientific research and applications in various industries

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