Analysis of the dormancy-inducible narK2 promoter in Mycobacterium bovis BCG

Upon depletion of oxygen, the obligate aerobe mycobacteria switch from grow th to a state of non-replicating persistence or dormancy. Here, we report t he first functional analysis of a dormancy-dependent mycobacterial promoter in Mycobacterium bovis BCG. Promoter probing using a 'lacZ reporter detect ed a dormancy-inducible promoter activity upstream of the coding sequence f or the putative nitrite extrusion protein NarK2. Primer extension analysis mapped a transcriptional start point 47 bp upstream of the narK2 start codo n. Deletion analysis revealed that the sequence -222 to -133 bp upstream fr om the transcriptional start point was required for basal and dormancy-indu cible reporter expression. The sequence +1 to +47 downstream of the transcr iptional start point had a strong inhibitory effect on the level of dormanc y-induced beta-galactosidase activity. The identification of apparent activ ating and inhibiting regions suggests that the narK2 promoter is at least u nder dual control. (C) 2000 Federation of European Microbiological Societie s. Published by Elsevier Science B.V. All rights reserved.