Genome flux by COG functional categories. (a) Flux. (b) Gain. (c) Loss. (d) Expansion. (e) Reduction. Designations of the functional categories (modified from ): C, energy production and conversion; D, cell division; E, amino acid metabolism and transport; F, nucleotide metabolism and transport; G, carbohydrate metabolism and transport; H, coenzyme metabolism; I, lipid metabolism; J, translation; K, transcription; L, replication and repair; M, membrane and cell wall structure and biogenesis; N, secretion and motility; O, post-translational modification, protein turnover and chaperone functions; P, inorganic ion transport and metabolism; Q, biosynthesis, transport and catabolism of secondary metabolites; R, general functional prediction only (typically, prediction of biochemical activity); S, function unknown; T, signal transduction; U, intracellular trafficking and secretion; V, defense systems; X, mobilome. COG, cluster of orthologous genes.