Nakano M M, Zuber P, Glaser P, Danchin A, Hulett F M
Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, Shreveport, Louisiana 71130-3932, USA.
J Bacteriol. 1996 Jul;178(13):3796-802. doi: 10.1128/jb.178.13.3796-3802.1996.
Bacillus subtilis can grow anaerobically in the presence of nitrate as a terminal electron acceptor. The two component regulatory proteins, ResD and ResE, and an anaerobic gene regulator, FNR, were previously shown to be indispensable for nitrate respiration in B. subtilis. Unlike Escherichia coli fnr, B. subtilis fnr transcription was shown to be highly induced by oxygen limitation. fnr is transcribed from its own promoter as well as from a promoter located upstream of narK, the first gene in the narK-fnr dicistronic operon. DNA fragments containing the narK promoter, the fnr promoter, and both of the promoters were used to construct three lacZ fusions to examine the transcriptional regulation of the narK-fnr operon. ResDE was found to be required for transcriptional activation of fnr from the fnr-specific promoter, and FNR was required for activation of narK-fnr transcription from the FNR-dependent narK operon promoter under anaerobiosis. In order to determine if the requirement for ResDE in nitrate respiration is solely to activate fnr transcription, fnr was placed under control of the IPTG (isopropyl-beta-D-thiogalactopyranoside)-inducible promoter, Pspac. The observed defect in anaerobic growth of a Pspac-fnr delta resDE mutant in the presence of IPTG indicated that resDE has an additional role in B. subtilis anaerobic gene regulation.
枯草芽孢杆菌在以硝酸盐作为末端电子受体时能够进行厌氧生长。先前已证明，双组分调节蛋白ResD和ResE以及一种厌氧基因调节因子FNR对于枯草芽孢杆菌的硝酸盐呼吸是不可或缺的。与大肠杆菌的fnr不同，枯草芽孢杆菌的fnr转录在氧限制条件下被高度诱导。fnr从其自身的启动子以及位于narK-fnr双顺反子操纵子第一个基因narK上游的一个启动子转录。含有narK启动子、fnr启动子以及这两个启动子的DNA片段被用于构建三个lacZ融合体，以检测narK-fnr操纵子的转录调控。结果发现，ResDE是从fnr特异性启动子转录激活fnr所必需的，而FNR是在厌氧条件下从依赖FNR的narK操纵子启动子转录激活narK-fnr所必需的。为了确定在硝酸盐呼吸中对ResDE的需求是否仅仅是为了激活fnr转录，将fnr置于IPTG（异丙基-β-D-硫代半乳糖苷）诱导型启动子Pspac的控制之下。在IPTG存在的情况下，Pspac-fnr ΔresDE突变体在厌氧生长中观察到的缺陷表明，resDE在枯草芽孢杆菌厌氧基因调控中具有额外的作用。
