Functional classification of the differentially expressed genes during growth of A. pleuropneumoniae S4074 in BHI-B according to TIGRFAM. AAB: amino acids biosynthesis; BCPC: biosynthesis of cofactors, prosthetic groups and carriers; CE: cell envelope; CP: cellular processes; CIM: central intermediary metabolism; DNA: DNA metabolism; EM: energy metabolism; FAPM: fatty acid and phospholipid metabolism; HUU: hypothetical proteins/unclassified/unknown; MEEF: mobile and extrachromosomal element functions; PF: protein fate; PS: protein synthesis; PPNN: purines, pyrimidines, nucleosides and nucleotides; RF: regulatory functions; TR: transcription and TBP: transport and binding proteins.