The KEGG database uses the NCBI taxonomy for classification of cellular organisms and viruses. For cellular organisms, the three- or four-letter KEGG organism codes are classified somewhat differently in the following Brite hierarchy files.

• 08601 KEGG organisms
• 08610 KEGG organisms in the NCBI taxonomy
• 08611 KEGG organisms in taxonomic ranks

08601 is a manually created taxonomy file using the simple hierarchy defined in the KEGG organism groups and the predefined order of organism codes with hsa (Homo sapiens) at the top. 08610 is computationally generated using the abbreviated lineage of the NCBI taxonomy keeping the order of organism codes defined in 08601. In addition, 08610 contains taxonomy IDs for GENES Addendum (ag) entries. 08611 is another computationally generated file for the KEGG organisms with fixed levels of taxonomic ranks: phylum, class, order, family, genus and species.

For viruses, the taxonomy IDs of KEGG Viruses (GENOME vtax category and GENES vg category) are classified according to the NCBI taxonomy, which is based on the ICTV taxonomy, with the Baltimore classification added by KEGG.

• 08620 KEGG viruses in the NCBI taxonomy
• 08621 KEGG viruses in taxonomic ranks

Both of these Brite hierarchy files are computationally generated and the lowest-level taxonomy IDs are linked to GENOME vtax entries. In the 08620 file the taxonomy IDs are shown in the full lineage of NCBI virus taxonomy, while the 08621 file is organized in the fixed levels of taxonomic ranks: realm, kingdom, phylum, class, order, family, genus and species.

Taxonomy mapping is the process to map genomic contents of KOs (K numbers), modules (M numbers) and other objects to a taxonomy file (see more details in KEGG Syntax). The result is usually viewed with the KEGG taxonomy browser, which is implemented as a special-purpose Brite hierarchy viewer. The fixed-level taxonomy files of 08611 for cellular organisms and 08621 for viruses are used as default. The browser has a zooming capability to adjust the bottom level of the taxonomic tree, for example, family or class in eukaryotes and species or genus in prokaryotes.

The result of taxonomy mapping may also be viewed in a tabular form (used to be called module table) summarizing distributions in taxonomic groups.

The taxonomic distribution of a single KO or module can be viewed from its entry page (such as K22014) through Taxonomy or Virus taxonomy button. Taxonomy mapping is performed using the default taxonomy file of 08611 or 08621.

This interface displays taxonomic distributions of KOs (K numbers) and modules (M numbers) as genomic features, optionally combined with user-defined data such as for phenotypic features using the Join operation of KEGG Mapper.

Select Taxonomy file: 08601 KEGG organisms 08610 KEGG organisms in the NCBI taxonomy 08611 KEGG organisms in taxonomic ranks

Enter K/M numbers    (Example) M00595 K16952 M00596

Enter user-defined data (Org codes and attributes)    (Example) org_keyword.txt

Or upload file:

This interface uses VOGs (virus ortholog groups) in addition to KOs for the virus taxonomy file.

Select Taxonomy file: 08620 KEGG viruses in the NCBI taxonomy 08621 KEGG viruses in taxonomic ranks

Enter K numbers and/or a vg identifier    (Example) vg:1486428 K23381

Enter user-defined data (tax id and attributes)    (Example) virus_disease.txt

Or upload file: