Bacterial Cell cycle & Development (BCcD), Biology of Microorganisms Research Unit (URBM), Namur Research Institute for Life Science (NARILIS), Universite de Namur, Namur, Belgium.
Laboratoire de Chimie Physique des Biomolécules, UCPTS, Namur Institute of Structured Matter (NISM), Namur Research Institute for Life Sciences (NARILIS), Universite de Namur, Namur, Belgium.
J Bacteriol. 2024 Sep 19;206(9):e0010724. doi: 10.1128/jb.00107-24. Epub 2024 Aug 12.
Potassium (K) is an essential physiological element determining membrane potential, intracellular pH, osmotic/turgor pressure, and protein synthesis in cells. Here, we describe the regulation of potassium uptake systems in the oligotrophic α-proteobacterium known as a model for asymmetric cell division. We show that can grow in concentrations from the micromolar to the millimolar range by mainly using two K transporters to maintain potassium homeostasis, the low-affinity Kup and the high-affinity Kdp uptake systems. When K is not limiting, we found that the gene is essential while inactivation does not impact the growth. In contrast, becomes critical but not essential and dispensable for growth in K-limited environments. However, in the absence of , mutations in were selected to improve growth in K-depleted conditions, likely by increasing the affinity of Kup for K. In addition, mutations in the KdpDE two-component system, which regulates expression, suggest that the inner membrane sensor regulatory component KdpD mainly works as a phosphatase to limit the growth when cells reach late exponential phase. Our data therefore suggest that KdpE is phosphorylated by another non-cognate histidine kinase. On top of this, we determined the KdpE-dependent and independent K transcriptome. Together, our work illustrates how an oligotrophic bacterium responds to fluctuation in K availability.IMPORTANCEPotassium (K) is a key metal ion involved in many essential cellular processes. Here, we show that the oligotroph can support growth at micromolar concentrations of K by mainly using two K uptake systems, the low-affinity Kup and the high-affinity Kdp. Using genome-wide approaches, we also determined the entire set of genes required for to survive at low K concentration as well as the full K-dependent regulon. Finally, we found that the transcriptional regulation mediated by the KdpDE two-component system is unconventional since unlike , the inner membrane sensor regulatory component KdpD seems to work rather as a phosphatase on the phosphorylated response regulator KdpE~P.
钾（K）是决定细胞膜电位、细胞内 pH 值、渗透压/膨压以及蛋白质合成的必需生理元素。在这里，我们描述了在寡营养 α-变形菌中的钾摄取系统的调节，该菌被用作不对称细胞分裂的模型。我们表明， 可以在从微摩尔到毫摩尔范围的浓度下生长，主要使用两种 K 转运体来维持钾的动态平衡，即低亲和力 Kup 和高亲和力 Kdp 摄取系统。当 K 不受到限制时，我们发现 基因是必需的，而 失活不会影响生长。相比之下， 在 K 限制环境中变得关键但不是必需的，而 是生长所必需的。然而，在没有 的情况下， 在 K 耗尽条件下的生长中选择了突变，可能是通过增加 Kup 对 K 的亲和力来提高生长。此外，KdpDE 双组分系统的突变，该系统调节 表达，表明内膜传感器调节成分 KdpD 主要作为一种磷酸酶起作用，以限制当细胞进入指数晚期时的生长。因此，我们的数据表明 KdpE 被另一种非同源组氨酸激酶磷酸化。除此之外，我们还确定了 KdpE 依赖和独立的 K 转录组。总的来说，我们的工作说明了贫营养细菌如何响应 K 可用性的波动。
钾（K）是一种参与许多重要细胞过程的关键金属离子。在这里，我们表明，贫营养菌 在 K 的微摩尔浓度下主要通过两种 K 摄取系统，低亲和力 Kup 和高亲和力 Kdp，支持生长。使用全基因组方法，我们还确定了在低 K 浓度下生存所需的整套基因以及完整的 K 依赖性调控子。最后，我们发现 KdpDE 双组分系统介导的转录调节是非传统的，因为与 不同，内膜传感器调节成分 KdpD 似乎在磷酸化的应答调节子 KdpE~P 上起磷酸酶的作用。
