Department of Biotechnology, All India Institute of Medical Sciences, New Delhi, India.
PLoS One. 2012;7(4):e35847. doi: 10.1371/journal.pone.0035847. Epub 2012 Apr 26.
The DevR(DosR) regulon is implicated in hypoxic adaptation and virulence of Mycobacterium tuberculosis. The present study was designed to decipher the impact of perturbation in DevR-mediated signaling on these properties.
METHODOLOGY/PRINCIPAL FINDINGS: M. tb complemented (Comp) strains expressing different levels of DevR were constructed in Mut1* background (expressing DevR N-terminal domain in fusion with AphI (DevR(N)-Kan) and in Mut2ΔdevR background (deletion mutant). They were compared for their hypoxia adaptation and virulence properties. Diverse phenotypes were noted; basal level expression (∼5.3±2.3 µM) when induced to levels equivalent to WT levels (∼25.8±9.3 µM) was associated with robust DevR regulon induction and hypoxic adaptation (Comp 9* and 10*), whereas low-level expression (detectable at transcript level) as in Comp 11* and Comp15 was associated with an adaptation defect. Intermediate-level expression (∼3.3±1.2 µM) partially restored hypoxic adaptation functions in Comp2, but not in Comp1* bacteria that co-expressed DevR(N)-Kan. Comp* strains in Mut1* background also exhibited diverse virulence phenotypes; high/very low-level DevR expression was associated with virulence whereas intermediate-level expression was associated with low virulence. Transcription profiling and gene expression analysis revealed up-regulation of the phosphate starvation response (PSR) in Mut1* and Comp11* bacteria, but not in WT/Mut2ΔdevR/other Comp strains, indicating a plasticity in expression pathways that is determined by the magnitude of signaling perturbation through DevR(N)-Kan.
CONCLUSIONS/SIGNIFICANCE: A minimum DevR concentration of ∼3.3±1.2 µM (as in Comp2 bacteria) is required to support HspX expression in the standing culture hypoxia model. The relative intracellular concentrations of DevR and DevR(N)-Kan appear to be critical for determining dormancy regulon induction, hypoxic adaptation and virulence. Dysregulated DevR(N)-Kan-mediated signaling selectively triggers the PSR in bacteria expressing no/very low level of DevR. Our findings illustrate the important role of appropriate two-component-mediated signaling in pathogen physiology and the resilience of bacteria when such signaling is perturbed.
DevR(DosR)调控子参与结核分枝杆菌的低氧适应和毒力。本研究旨在破译 DevR 介导的信号转导扰动对这些特性的影响。
方法/主要发现：在 Mut1背景下（表达与 AphI 融合的 DevR N 端结构域（DevR（N）-Kan））构建了表达不同水平 DevR 的结核分枝杆菌互补（Comp）菌株，并在 Mut2ΔdevR 背景下（缺失突变体）。比较它们的低氧适应和毒力特性。注意到不同的表型；在诱导至与 WT 水平相当的水平（约 25.8±9.3 µM）时，基础水平表达（约 5.3±2.3 µM）与强大的 DevR 调控子诱导和低氧适应相关（Comp 9和 10*），而在 Comp 11和 Comp15 中检测到的低水平表达（在转录水平上可检测到）与适应缺陷相关。中间水平表达（约 3.3±1.2 µM）部分恢复了 Comp2 中的低氧适应功能，但在共表达 DevR（N）-Kan 的 Comp1细菌中没有。Mut1背景下的 Comp菌株也表现出不同的毒力表型；高/极低水平的 DevR 表达与毒力相关，而中间水平的表达与低毒力相关。转录谱分析和基因表达分析显示，在 Mut1和 Comp11细菌中，磷酸盐饥饿反应（PSR）上调，但在 WT/Mut2ΔdevR/其他 Comp 株中没有，表明表达途径具有可塑性，这取决于通过 DevR（N）-Kan 进行信号转导的幅度。
结论/意义：在静置培养低氧模型中，需要约 3.3±1.2 µM（如 Comp2 细菌）的最小 DevR 浓度来支持 HspX 的表达。DevR 和 DevR（N）-Kan 的相对细胞内浓度似乎对于确定休眠调控子诱导、低氧适应和毒力至关重要。失调的 DevR（N）-Kan 介导的信号转导选择性地触发在表达无/低水平 DevR 的细菌中触发 PSR。我们的发现说明了适当的双组分介导的信号在病原体生理学中的重要作用，以及当这种信号受到干扰时细菌的弹性。
