Fundación Instituto Leloir, IIBBA-CONICET, Patricias Argentinas, Buenos Aires, Argentina.
PLoS One. 2018 Apr 10;13(4):e0194486. doi: 10.1371/journal.pone.0194486. eCollection 2018.
Many signaling pathways that control cellular development, cell-cycle progression and nutritional versatility have been studied in Caulobacter crescentus. For example, it was suggested that the response regulator NtrX is conditionally essential for this bacterium and that it might be necessary for responding to a signal produced in phosphate-replete minimal medium. However, such signal has not been identified yet and the role of NtrX in C. crescentus biology remains elusive. Here, using wild-type C. crescentus and a strain with a chromosomally myc-tagged ntrX gene, we demonstrate that high concentrations of phosphate (10 mM) regulate ntrX transcription and the abundance of the protein. We also show that the pH of the medium acts as a switch able to regulate the phosphorylation status of NtrX, promoting its phosphorylation under mildly acidic conditions and its dephosphorylation at neutral pH. Moreover, we demonstrate that the ntrX gene is required for survival in environments with low pH and under acidic stress. Finally, we prove that NtrX phosphorylation is also triggered by low pH in Brucella abortus, a pathogenic alphaproteobacterium. Overall, our work contributes to deepen the general knowledge of this system and provides tools to elucidate the NtrX regulon.
许多控制细胞发育、细胞周期进程和营养多样性的信号通路已在新月柄杆菌中进行了研究。例如，有人提出，响应调节剂 NtrX 对这种细菌是有条件必需的，它可能是对磷酸盐充足的基础培养基中产生的信号做出反应所必需的。然而，这种信号尚未被鉴定出来，NtrX 在新月柄杆菌生物学中的作用仍然难以捉摸。在这里，我们使用野生型新月柄杆菌和带有染色体 myc 标记的 ntrX 基因的菌株，证明了高浓度的磷酸盐（10 mM）调节 ntrX 的转录和蛋白丰度。我们还表明，培养基的 pH 值作为一个开关，可以调节 NtrX 的磷酸化状态，在酸性条件下促进其磷酸化，在中性 pH 值下使其去磷酸化。此外，我们证明 ntrX 基因是在低 pH 值环境中和酸性胁迫下生存所必需的。最后，我们证明 NtrX 的磷酸化也被布鲁氏菌 abortus 触发，这是一种致病性的α变形菌。总的来说，我们的工作有助于加深对该系统的一般认识，并提供了阐明 NtrX 调控基因的工具。
