Influence of Zur and zinc availability in the expression of Zur-repressed genes. Transcriptional fusions of znuK, znuL, znuM, zrpWX and znuGHI promoter regions to the lacZ reporter gene were introduced into NA1000, MM69, MM69 (pUJ) and MM69 (pUJ-zur) strains, and grown under different regimens of zinc availability. Expression was determined by β-galactosidase activity assays. White bars indicate M2 medium supplied with 500 μM ZnCl2, light grey bars indicate M2 medium supplied with 500 μM EDTA and dark grey bars indicate M2 medium supplied with 500 μM ZnCl2 and 500 μM EDTA. In the complementation analysis, MM69 strain harboring plasmid pUJ142 without insert (−) or carrying the zur gene (+) was used. The results shown are the average of at least three experiments. Error bars indicate standard deviations.