Department of Biological Sciences, Ohio University, Athens, OH, USA.
Cell Biology and Metabolism Program, NICHD, NIH, Bethesda, MD, USA.
Microbiologyopen. 2017 Jun;6(3). doi: 10.1002/mbo3.442. Epub 2017 Jan 26.
Like most bacteria, Shigella must maintain a precise balance between the necessity and toxicity of iron; a balance that is achieved, at least in part, by regulating the production of bacterial iron acquisition systems in response to specific environmental signals. Using the Shigella heme utilization (Shu) system, S. dysenteriae is able to acquire iron from heme, a potentially rich source of nutritional iron within the otherwise iron-limited environment of the human host. Investigations presented within reveal two distinct molecular mechanisms underlying previously uncharacterized transcriptional and translational regulation of shuT, a gene encoding the periplasmic-binding component of the Shu system. While shuT transcription is regulated in response to iron availability via a process dependent upon the global regulator Fur and a Fur-binding site located immediately downstream of the promoter, shuT translation is regulated in response to environmental temperature via the activity of an RNA thermometer located within the 5' untranslated region of the gene. Such complex regulation likely increases the fitness of S. dysenteriae by ensuring maximal ShuT production when the pathogen is within the iron-limited and relatively warm environment of the infected host, the only environment in which heme will be encountered as a potential source of essential iron.
与大多数细菌一样，志贺氏菌必须在铁的必要性和毒性之间保持精确的平衡；这种平衡至少部分是通过调节细菌铁摄取系统的产生来实现的，以响应特定的环境信号。志贺氏菌利用血红素利用（Shu）系统能够从血红素中获取铁，血红素是人类宿主中通常缺铁环境中潜在的丰富营养铁源。本研究揭示了以前未表征的 shuT 转录和翻译调控的两种不同分子机制，shuT 基因编码 Shu 系统的周质结合成分。尽管 shuT 的转录受到 Fur 全局调节因子和位于启动子下游的 Fur 结合位点的影响，从而响应铁的可用性进行调节，但 shuT 的翻译受到位于基因 5'非翻译区的 RNA 温度计的活性的影响，从而响应环境温度进行调节。这种复杂的调控可能会通过确保在病原体处于感染宿主的缺铁和相对温暖的环境中时，最大限度地产生 ShuT，从而提高志贺氏菌的适应性，因为在这种环境中，血红素将作为必需铁的潜在来源被遇到。
