Tanner Jennifer R, Patel Palak G, Hellinga Jacqueline R, Donald Lynda J, Jimenez Celine, LeBlanc Jason J, Brassinga Ann Karen C
Department of Microbiology, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada.
Department of Pathology, Medicine, and Microbiology & Immunology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada.
J Bacteriol. 2017 Feb 14;199(5). doi: 10.1128/JB.00690-16. Print 2017 Mar 1.
Nominally an environmental organism, is an intracellular parasite of protozoa but is also the causative agent of the pneumonia termed Legionnaires' disease, which results from inhalation of aerosolized bacteria by susceptible humans. Coordination of gene expression by a number of identified regulatory factors, including OxyR, assists in adapting to the stresses of changing environments. OxyR (OxyR) is an ortholog of OxyR; however, OxyR was shown elsewhere to be functionally divergent, such that it acts as a transcription regulator independently of the oxidative stress response. In this study, the use of improved gene deletion methods has enabled us to generate an unmarked in-frame deletion of in Lack of OxyR did not affect growth or intracellular growth in protozoa and U937-derived macrophages. The expression of OxyR does not appear to be regulated by CpxR, even though purified recombinant CpxR bound a DNA sequence similar to that reported for CpxR elsewhere. Surprisingly, a lack of OxyR resulted in elevated activity of the promoters located upstream of and the operon, and OxyR directly bound to these promoter regions, suggesting that OxyR is a direct repressor. Interestingly, a strain overexpressing OxyR demonstrated reduced intracellular growth in but not in U937-derived macrophages, suggesting that balanced expression control of the two-component CpxRA system is necessary for survival in protozoa. Taken together, this study suggests that OxyR is a functionally redundant transcriptional regulator in under the conditions evaluated herein. is an environmental pathogen, with its transmission to the human host dependent upon its ability to replicate in protozoa and survive within its aquatic niche. Understanding the genetic factors that contribute to survival within each of these unique environments will be key to limiting future point-source outbreaks of Legionnaires' disease. The transcriptional regulator OxyR (OxyR) has been previously identified as a potential regulator of virulence traits warranting further investigation. This study demonstrated that is nonessential for survival and via mutational analysis. While the mechanisms of how OxyR expression is regulated remain elusive, this study shows that OxyR negatively regulates the expression of the two-component system necessary for intracellular survival in protozoa.
通常作为一种环境微生物，它是原生动物的细胞内寄生虫，但也是被称为军团病的肺炎的病原体，这种肺炎是由易感人群吸入雾化细菌引起的。包括OxyR在内的一些已确定的调节因子对基因表达的协调作用，有助于其适应不断变化的环境压力。OxyR（OxyR）是OxyR的直系同源物；然而，在其他地方已表明OxyR在功能上存在差异，以至于它作为一种转录调节因子独立于氧化应激反应发挥作用。在本研究中，使用改进的基因缺失方法使我们能够在缺乏OxyR的情况下产生无标记的框内缺失。缺乏OxyR并不影响其在原生动物和U937衍生巨噬细胞中的生长或细胞内生长。尽管纯化的重组CpxR结合了与其他地方报道的CpxR相似的DNA序列，但OxyR的表达似乎不受CpxR调节。令人惊讶的是，缺乏OxyR导致位于和操纵子上游的启动子活性升高，并且OxyR直接结合到这些启动子区域，这表明OxyR是一种直接阻遏物。有趣的是，过表达OxyR的菌株在原生动物中细胞内生长减少，但在U937衍生巨噬细胞中没有减少，这表明双组分CpxRA系统的平衡表达控制对于在原生动物中生存是必要的。综上所述，本研究表明在本文评估的条件下，OxyR在中是一种功能冗余的转录调节因子。是一种环境病原体，其传播给人类宿主取决于其在原生动物中复制并在其水生生态位中生存的能力。了解有助于其在这些独特环境中生存任一环境中的遗传因素，将是限制未来军团病点状源爆发的关键。转录调节因子OxyR（OxyR）先前已被确定为毒力特征的潜在调节因子，值得进一步研究。本研究通过突变分析表明对于生存和并非必需。虽然OxyR表达如何被调节的机制仍然难以捉摸，但本研究表明OxyR负调节原生动物细胞内存活所必需的双组分系统的表达。
