Characterization of the mxd promoter. (A) Schematic representation of the mxd transcription start site (+1). (B) Wild type strains carrying reporter constructs with truncated mxdA up-stream regions transcriptionally fused to lacZ were grown under complex media conditions. The different strains were assayed for β-galactosidase activity, expressed as Miller Units (MU). The cartoon on the left side shows a graphical representation of the truncated P
::lacZ constructs. The construct marked 0 contains a fragment corresponding to 150 bp upstream of the mxdA translation initiation site, representing the approximate transcription start site. The constructs marked -100, -150 and -300 contain fragments corresponding to 100, 150 and 300 bp upstream of the approximate transcription start site and correspond to strains AS834, AS833 and AS832. The graph on the right side shows the corresponding β-galactosidase activities (y-axis) for cells harvested after 2 h, 4 h, 6 h, 10 h and 24 h (x-axis). A predicted ArcA binding site at position -112 bp is indicated.