Rhodococcus sp. strain TFB is a versatile gram-positive bacterium able to grow on a wide variety of aromatic compounds as carbon and energy sources. Since the strain is refractory to genetic analysis, a proteomic approach was used to study the metabolic pathways involved in the catabolism of such compounds by analyzing differentially induced proteins. The most marked difference was observed when the proteome profiles of phthalate-grown cells were compared with those cultured in the presence of tetralin- or naphthalene, suggesting that different metabolic pathways are involved in the degradation of mono- and polyaromatic compounds. Comparison with the proteome of glucose-grown cells indicated that each pathway was specifically induced by the corresponding aromatic compound. A combination of proteomics and molecular biology led to the identification of 14 proteins (65-80% identical to known Pht proteins) that describe a complete pathway for the catabolism of phthalate to central metabolites via intradiol cleavage of protochatechuic acid. Chaperonins were also induced in phthalate-grown cells, indicating that growth on this compound induces a stress response. Absence of catabolite repression by glucose was observed by both transcriptional and proteome analysis, suggesting that Rhodococcus sp. strain TFB may have advantages over other tightly regulated strains in bioremediation.