Department of Microbiology, The Forsyth Institute, Cambridge, Massachusetts, United States of America.
PLoS One. 2013 May 6;8(5):e63180. doi: 10.1371/journal.pone.0063180. Print 2013.
Porphyromonas gingivalis is a Gram-negative oral anaerobe which is strongly associated with periodontal disease. Environmental changes in the gingival sulcus trigger the growth of P. gingivalis and a concurrent shift from periodontal health to disease. Bacteria adjust their physiology in response to environmental changes and gene regulation by two-component phospho-relay systems is one mechanism by which such adjustments are effected. In P. gingivalis RprY is an orphan response regulator and previously we showed that the RprY regulon included genes associated with oxidative stress and sodium metabolism. The goals of the present study were to identify environmental signals that induce rprY and clarify the role of the regulator in the stress response. In Escherichia coli an RprY-LacZ fusion protein was induced in sodium- depleted medium and a P. gingivalis rprY mutant was unable to grow in similar medium. By several approaches we established that sodium depletion induced up-regulation of genes involved in oxidative stress. In addition, we demonstrated that RprY interacted directly with the promoters of several molecular chaperones. Further, both genetic and transcription data suggest that the regulator acts as a repressor. We conclude that RprY is one of the regulators that controls stress responses in P. gingivalis, possibly by acting as a repressor since an rprY mutant showed a superstress reponse in sodium-depleted medium which we propose inhibited growth.
牙龈卟啉单胞菌是一种革兰氏阴性口腔厌氧菌，与牙周病密切相关。牙龈沟内环境的变化会刺激牙龈卟啉单胞菌的生长，并导致牙周健康向疾病状态转变。细菌会根据环境变化调整其生理机能，而双组分磷酸传递系统的基因调控是实现这种调整的一种机制。在牙龈卟啉单胞菌中，RprY 是一个孤儿反应调节剂，之前我们已经表明，RprY 调控子包含与氧化应激和钠代谢相关的基因。本研究的目的是确定诱导 rprY 的环境信号，并阐明该调节剂在应激反应中的作用。在大肠杆菌中，RprY-LacZ 融合蛋白在缺钠培养基中被诱导，而牙龈卟啉单胞菌 rprY 突变体无法在类似的培养基中生长。通过多种方法，我们确定了钠耗竭诱导了与氧化应激相关的基因的上调。此外，我们还证明了 RprY 与几种分子伴侣的启动子直接相互作用。此外，遗传和转录数据表明，该调节剂作为一种阻遏物起作用。我们得出结论，RprY 是控制牙龈卟啉单胞菌应激反应的调节剂之一，可能通过作为一种阻遏物起作用，因为 rprY 突变体在缺钠培养基中表现出超级应激反应，我们推测这抑制了生长。
