活动细菌在植物表面的定植中具有竞争优势,以建立最终支持植物健康的有益协会。植物分泌物不仅用作细菌的主要生长底物,而且还用作细菌趋化性引诱剂。已经记录了许多植物来源的化合物和相应的趋化性传感器,然而,甲醇传感器,植物释放的主要挥发性化合物之一,尚未确定。甲基杆菌物种是普遍存在的植物表面共生,甲基营养细菌.一种促进植物生长的细菌,水分枝杆菌菌株22A表现出对甲醇的趋化性(甲趋化)。它的基因组编码52个甲基接受趋化蛋白(MCPs),其中我们鉴定了三种MCP(甲基化蛋白,MtpA,MtpB,和MtpC)负责甲基化。MCPs的三重基因突变体没有表现出甲基化,较慢地聚集到植物组织,在植物上的定殖效率低于野生型,表明甲基化介导了植物-甲基杆菌共生的启动,并参与了植物的增殖。为了检查这些MCP是如何进行甲基化的,我们产生了MCP的多个基因敲除,和Ca2依赖性MxaFI和镧系元素(Ln3)依赖性XoxF甲醇脱氢酶(MDHs),其表达受Ln3+的存在调节。MtpA被发现是一种细胞溶质传感器,可以进行甲醛出租车(formtaxis),以及MDHs产生甲醛时的甲基化。MtpB包含dCache域,并响应La3表现出差异细胞定位。La3+诱导MtpB表达,及其活性需要XoxF1。MtpC表现出典型的细胞极定位,所需的MxaFI活动,并且在MxbDM下调节,MxbDM也是MxaF表达所需的。菌株22A的甲基化是由三个独立的MCP实现的,其中两个监测Ln3+调节的MDHs对甲醇的氧化,其中一个监测常见的甲醇氧化产物,甲醛。我们认为甲醇代谢相关的趋化性是甲基杆菌在植物上有效定殖的关键因素。
Motile bacteria take a competitive advantage in colonization of plant surfaces to establish beneficial associations that eventually support plant health. Plant exudates serve not only as primary growth substrates for bacteria but also as bacterial chemotaxis attractants. A number of plant-derived compounds and corresponding chemotaxis sensors have been documented, however, the sensors for methanol, one of the major volatile compounds released by plants, have not been identified. Methylobacterium species are ubiquitous plant surface-symbiotic, methylotrophic bacteria. A plant-growth promoting bacterium, M. aquaticum strain 22A exhibits chemotaxis toward methanol (methylotaxis). Its genome encodes 52 methyl-accepting chemotaxis proteins (MCPs), among which we identified three MCPs (methylotaxis proteins, MtpA, MtpB, and MtpC) responsible for methylotaxis. The triple gene mutant of the MCPs exhibited no methylotaxis, slower gathering to plant tissues, and less efficient colonization on plants than the wild type, suggesting that the methylotaxis mediates initiation of plant-Methylobacterium symbiosis and engages in proliferation on plants. To examine how these MCPs are operating methylotaxis, we generated multiple gene knockouts of the MCPs, and Ca2+-dependent MxaFI and lanthanide (Ln3+)-dependent XoxF methanol dehydrogenases (MDHs), whose expression is regulated by the presence of Ln3+. MtpA was found to be a cytosolic sensor that conducts formaldehyde taxis (formtaxis), as well as methylotaxis when MDHs generate formaldehyde. MtpB contained a dCache domain and exhibited differential cellular localization in response to La3+. MtpB expression was induced by La3+, and its activity required XoxF1. MtpC exhibited typical cell pole localization, required MxaFI activity, and was regulated under MxbDM that is also required for MxaF expression. Strain 22A methylotaxis is realized by three independent MCPs, two of which monitor methanol oxidation by Ln3+-regulated MDHs, and one of which monitors the common methanol oxidation product, formaldehyde. We propose that methanol metabolism-linked chemotaxis is the key factor for the efficient colonization of Methylobacterium on plants.