KEGG and COG (Clusters of Orthologous Groups) are two widely used databases that offer organism-independent annotation for genes from shotgun microbiome studies.
In MicrobiomeAnalyst, the KO annotation and visualization is mainly based on the global metabolic maps (ko01100). It contains 161 KEGG pathways and 236 KEGG modules. Users can perform mapping and visual exploration as stack area plot or metabolic networks. KEGG KO annotations offer a more detailed view on the metabolic capacity of the microbial community, with potential mechanistic interpretation.
The COG annotation provides 25 functional categories related to METABOLISM, CELLULAR PROCESSES AND SIGNALING, INFORMATION STORAGE AND PROCESSING. They may provide a broader classification or more functional coverage as compared to KEGG. COG groups together functions that are “related” according to the common biochemical knowledge, although no evidence of this relatedness is recorded. In addition, many COG categories contain COGs that are rather loosely associated with certain biological activity. Users should be cautious to use the presence or absence from the COG pathway profile as an indication of the presence or absence of a certain metabolic pathway.