Distribution of differentially expressed genes. E. coli W3110 (A) and its ada mutant (B) strains at each time profile (0.5, 1.5 and 3.9 h) were sampled and compared after MMS treatment based on the corresponding untreated control. The up- or down-regulated genes at each time point were counted after classification by functional categories according to the E. coli genome information . Categories: Structure, cell structure, membrane proteins, structural proteins; Transport, transport and binding proteins, putative transport proteins; Process, cell processes including adaptation and protection; DNA, DNA replication, recombination, modification and repair; Transcription, transcription, RNA processing and degradation; Translation, translation, post-translational modification; Energy, energy metabolism; Carbon, carbon compound catabolism; Amino acid, amino acid biosynthesis and metabolism; Nucleotide, nucleotide biosynthesis and metabolism; Fatty acid, fatty acid and phospholipid metabolism; Intermediate, central intermediary metabolism; Regulation, regulatory function, putative regulatory proteins; Cofactor, biosynthesis of cofactors, prosthetic groups and carriers; Phage, phage, transposon or plasmid. The number of total genes was indicated at the bottom of each heat map.