Cluster of orthologous genes

COGs stands for Clusters of Orthologous Genes. The database was initially created in 1997 (Tatusov et al., PMID: 9381173) followed by several updates, most recently in 2014 (Galperin et al., PMID: 25428365). The current update includes complete genomes of 1,187 bacteria and 122 archaea that map into 1,234 genera. The new features include ~250 updated COG annotations with corresponding references and PDB links, where available; new COGs for proteins involved in CRISPR-Cas immunity, sporulation, and photosynthesis, and the lists of COGs grouped by pathways and functional systems.