Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, 70803, USA.
Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA, USA.
Sci Rep. 2019 Feb 26;9(1):2797. doi: 10.1038/s41598-019-39095-4.
The genus Vibrio includes serious human pathogens, and mollusks are a significant reservoir for species such as V. vulnificus. Vibrio species encode PecS, a member of the multiple antibiotic resistance regulator (MarR) family of transcription factors; pecS is divergently oriented to pecM, which encodes an efflux pump. We report here that Vibrio species feature frequent duplications of pecS-pecM genes, suggesting evolutionary pressures to respond to distinct environmental situations. The single V. vulnificus PecS binds two sites within the pecS-pecM intergenic region with K = 0.3 ± 0.1 nM, a binding that is attenuated by the ligands xanthine and urate, except when promoter DNA is saturated with PecS. A unique target is found in the intergenic region between genes encoding the nitric oxide sensing transcription factor, NsrR, and nod; the nod-encoded nitric oxide dioxygenase is important for preventing nitric oxide stress. Reporter gene assays show that PecS-mediated repression of gene expression can be relieved in presence of ligand. Since xanthine and urate are produced as part of the oxidative burst during host defenses and under molluscan hypoxia, we propose that these intermediates in the host purine degradation pathway function to promote bacterial survival during hypoxia and oxidative stress.
弧菌属包括严重的人类病原体，而软体动物是弧菌属物种（如创伤弧菌）的重要宿主。弧菌属编码 PecS，它是多抗生素耐药调节因子（MarR）家族转录因子的成员；pecS 与 pecM 呈反向排列，pecM 编码外排泵。我们在这里报告称，弧菌属经常发生 pecS-pecM 基因的重复，表明它们面临着应对不同环境情况的进化压力。单一的创伤弧菌 PecS 与 pecS-pecM 基因间区的两个位点结合，Kd 值为 0.3±0.1 nM，这种结合会被黄嘌呤和尿酸所减弱，除非启动子 DNA被 PecS 完全饱和。在编码一氧化氮感应转录因子 NsrR 和 nod 的基因之间的基因间区发现了一个独特的靶标；nod 编码的一氧化氮双加氧酶对于防止一氧化氮应激很重要。报告基因检测表明，在存在配体的情况下， PecS 介导的基因表达抑制可以得到缓解。由于黄嘌呤和尿酸是宿主防御过程中氧化爆发和软体动物缺氧时产生的嘌呤降解途径的一部分，我们提出这些宿主嘌呤降解途径的中间产物可以促进细菌在缺氧和氧化应激期间的存活。
