Regulatory region of Ecol\lacZrho.NEE50Δs (including 700bp rho promoter fragment that lacks all four sna-binding sites and has one synthetic sna-binding site 50bp downstream of d4, oriented with the dl4 site closest to the basal promoter) is fused 3' to the lacZ coding region, and two kni binding sites introduced 5' of lacZ with the 3' end of the proximal binding site at -55bp.