We systematically assessed, through RT-PCR, dynamic transcriptional activity of the TOL Pr, Ps, Pu, Pm and chromosomal PbenR and PbenA promoters upon entry of different toluene concentrations until substrate depletion in batch cultures.

We revealed the interconnection of the two pathways due to TOL Pm and chromosomal PbenA cross-up-regulation by transcription factors of both pathways.

Chromosomal PbenR activation was achieved due to benzoate presence, an intermediate of toluene degradation formed through TOL metabolic pathway activity.

TOL Pm oscillates at higher toluene concentration level underlying regulation by more than known transcription factors.

Pr down-regulation, although common, is not evident below 0.3 mM of toluene regardless of the initial substrate amount.