Hierarchical dynamics of a transcription factors network in E. coli.

In the present work we study the transcription-factor regulatory network that controls the synthesis of flagella in E. coli. Our objective is to address how the transcription-factor dynamics (in terms of their promoter activities and associated rates) correlate with their positions in the hierarchical organization of this regulatory network. Our results suggest that global-regulator promoters express at higher rates than those of local regulators, particularly when the bacterial populations are actively growing. Furthermore, promoter activity decreases together with the rate of cellular division. And finally, local-regulator promoters reach their maximal activity later than global-regulator promoters do. In summary, our results suggest a strong correlation between promoter activities and their hierarchical organization in this particular regulatory network.