EVOLUTION OF BACTERIAL AROMATIC-DEGRADING OPERONS BY ALTERATION OF THE MECHANISM OF TRANSCRIPTIONAL REGULATION

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Anthranilate (AN)-dependant P_<ant> promoter regulates the transcription of ant and car operons of P. resinovorans strain CA10, which encode the enzymes involved in CAR-degradation to AN and AN conversion to catechol, respectively. Genetic region involved in the transcriptional activation, a regulator protein, an effector molecule, and transcriptional start points of P_<ant> promoter have been characterized. δ^s・dependant near-constitutive P_<carAa> promoter is also involved in the transcription of car operon. P_<ant> promoter is originally located in the upstream region of ant operon, and the transposition of ISPre1 creates the additional copy of P_<ant> at the upstream of car operon. Resultantly, car operon became to be also induced strongly by AN, which is a metabolic intermediate of CAR.New CAR-degrading bacteria have been isolated from environmental samples. Genetic analyses of CAR-degrading car operons revealed that car operon of Janthinohacterium sp. strain J3 is an ancestral-type of that of P. resinovorans strain CA10. car operon of strain J3 is regulated by P_<u13> promoter, which is regulated by transcriptional repressor CarR. The effecter molecule of CarR is an unstable meta-cleavage compound in CAR degradative pathway. Trascriptional regulation mechanism and the expression profile in car operons of strain J3 are clearly different from that of strain CA10. It is shown that the recruitment of P_<ant> promoter by ISPre1 transposition has resulted in the effective CAR-degrading ability.