The NCBI Taxonomy staff places square brackets around the genus for some species (for example [Candida] auris) to indicate that they are misclassified*, meaning placed incorrectly in a higher taxonomic rank. The term misclassified refers to systematics which is one of three broad areas within the science of taxonomy:

  1. nomenclature — the naming of organisms (biological taxa)
  2. taxonomy sensu stricto (taxonomy in the narrow sense) — the description of named taxa
  3. systematics — the arrangement of named and described taxa in a scientifically meaningful hierarchy

In the [Candida] auris example, researchers currently established that this species does not belong to the genus Candida. The species is now awaiting to be formally renamed through the appropriate Code of Nomenclature, but until then the incorrect genus is indicated by the square brackets. Using square brackets for misclassified species has been used in bacteriology. The NCBI Taxonomy has recently expanded this convention to other organisms, such as Fungi (yeasts).

See also how the convention of using square brackets affects the file naming convention on the FTP site.

*Note: You should not confuse the term with misidentified that indicates that a specific organism has been incorrectly identified as belonging to a particular taxon that is in and of itself legitimately classified. A researcher might isolate a bacterium from soil and identify it as belonging to the species Bacillus subtilis when in fact it is a strain of Bacillus cereus. Both the names Bacillus subtilis and Bacillus cereus are properly classified as two different species of the genus Bacillus, but this particular isolate has been misidentified.

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