Department of Biological Sciences, Life Sciences I, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA.
Lehrstuhl für Genetik, Universität Regensburg, Regensburg, Germany.
J Bacteriol. 2018 Feb 23;200(6). doi: 10.1128/JB.00614-17. Print 2018 Mar 15.
The chemosensory system in has several important deviations from the widely studied enterobacterial paradigm. To better understand the differences between the two systems and how they are optimally tuned, we determined the cellular stoichiometry of the methyl-accepting chemotaxis proteins (MCPs) and the histidine kinase CheA in Quantitative immunoblotting was used to determine the total amount of MCPs and CheA per cell in The MCPs are present in the cell in high abundance (McpV), low abundance (IcpA, McpU, McpX, and McpW), and very low abundance (McpY and McpZ), whereas McpT was below the detection limit. The approximate cellular ratio of these three receptor groups is 300:30:1. The chemoreceptor-to-CheA ratio is 23.5:1, highly similar to that seen in (23:1) and about 10 times higher than that in (3.4:1). Different from , the high-abundance receptors in are lacking the carboxy-terminal NWETF pentapeptide that binds the CheR methyltransferase and CheB methylesterase. Using transcriptional fusions, we showed that chemoreceptors are positively controlled by the master regulators of motility, VisNR and Rem. In addition, FlbT, a class IIA transcriptional regulator of flagellins, also positively regulates the expression of most chemoreceptors except for McpT and McpY, identifying chemoreceptors as class III genes. Taken together, these results demonstrate that the chemosensory complex and the adaptation system in deviates significantly from the established enterobacterial paradigm but shares some similarities with The symbiotic soil bacterium is of great agricultural importance because of its nitrogen-fixing properties, which enhances growth of its plant symbiont, alfalfa. Chemotaxis provides a competitive advantage for bacteria to sense their environment and interact with their eukaryotic hosts. For a better understanding of the role of chemotaxis in these processes, detailed knowledge on the regulation and composition of the chemosensory machinery is essential. Here, we show that chemoreceptor gene expression in is controlled through the main transcriptional regulators of motility. Chemoreceptor abundance is much lower in than in and Moreover, the chemoreceptor-to-kinase CheA ratio is different from that of but similar to that of .
化感系统在 方面与广泛研究的肠杆菌范式有几个重要的偏差。为了更好地理解这两个系统之间的差异以及它们如何被最佳地调整，我们确定了甲基接受趋化性蛋白（MCP）和组氨酸激酶 CheA 的细胞化学计量在 中。定量免疫印迹用于确定 中每个细胞的 MCP 和 CheA 的总量。MCP 以高丰度（McpV）、低丰度（IcpA、McpU、McpX 和 McpW）和极低丰度（McpY 和 McpZ）存在于细胞中，而 McpT 低于检测限。这三个受体组的大致细胞比例为 300:30:1。Chemoreceptor 与 CheA 的比值为 23.5:1，与 中观察到的非常相似（23:1），约是 中的 10 倍（3.4:1）。与 不同， 中的高丰度受体缺乏与 CheR 甲基转移酶和 CheB 甲酯酶结合的羧基末端 NWETF 五肽。使用转录融合，我们表明运动的主要调节剂 VisNR 和 Rem 正向控制趋化受体。此外，鞭毛的 IIA 类转录调节剂 FlbT 也正向调节除 McpT 和 McpY 之外的大多数趋化受体的表达，将趋化受体鉴定为 III 类基因。总之，这些结果表明， 中的化感复合物和适应系统与已建立的肠杆菌范式有很大的偏差，但与 有一些相似之处。共生土壤细菌 因其固氮特性而具有重要的农业意义，这增强了其植物共生体紫花苜蓿的生长。趋化作用为细菌感知环境和与真核宿主相互作用提供了竞争优势。为了更好地理解趋化作用在这些过程中的作用，详细了解化感机械的调节和组成是必不可少的。在这里，我们表明， 中的趋化受体基因表达受运动的主要转录调节剂控制。与 和 相比， 中的趋化受体丰度要低得多。此外，趋化受体与激酶 CheA 的比值与 不同，但与 相似。
