Bacteria navigate their way often as individual cells through their chemical and biological environment in aqueous medium or across solid surfaces. They swim when starved or in response to physical and chemical stimuli. Flagella-driven chemotaxis in bacteria has emerged as a paradigm for both signal transduction and cellular decision-making. By altering motility, bacteria swim toward nutrient-rich environments, movement modulated by their chemotaxis systems with the addition of pili for surface movement. The numbers and types of chemoreceptors reflect the bacterial niche and lifestyle, with those adapted to complex environments having diverse metabolic capabilities, encoding far more chemoreceptors in their genomes. The Alpha-proteobacteria typify the latter case, with soil bacteria such as rhizobia, endosymbionts of legume plants, where motility and chemotaxis are essential for competitive symbiosis initiation, among other processes. This review describes the current knowledge of motility and chemotaxis in six model soil bacteria: Sinorhizobium meliloti, Agrobacterium fabacearum, Rhizobium leguminosarum, Azorhizobium caulinodans, Azospirillum brasilense, and Bradyrhizobium diazoefficiens. Although motility and chemotaxis systems have a conserved core, rhizobia possess several modifications that optimize their movements in soil and root surface environments. The soil provides a unique challenge for microbial mobility, since water pathways through particles are not always continuous, especially in drier conditions. The effectiveness of symbiont inoculants in a field context relies on their mobility and dispersal through the soil, often assisted by water percolation or macroorganism movement or networks. Thus, this review summarizes the factors that make it essential to consider and test rhizobial motility and chemotaxis for any potential inoculant.

中文翻译：

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根瘤菌趋化性和运动系统在土壤中发挥作用。

细菌通常作为单个细胞在水性介质中或穿过固体表面的化学和生物环境中导航。它们在饥饿或对物理和化学刺激做出反应时游泳。细菌中鞭毛驱动的趋化性已成为信号转导和细胞决策的范例。通过改变运动性，细菌游向营养丰富的环境，运动由它们的趋化系统调节，并添加菌毛进行表面运动。化学感受器的数量和类型反映了细菌生态位和生活方式，适应复杂环境的化学感受器具有不同的代谢能力，在其基因组中编码更多的化学感受器。α-变形菌是后一种情况的典型，土壤细菌如根瘤菌、豆科植物的内共生菌、其中运动性和趋化性对于竞争性共生启动等过程至关重要。这篇综述描述了六种模型土壤细菌的运动性和趋化性的当前知识：苜蓿根瘤菌、农杆菌、豆科根瘤菌、固氮菌、巴西固氮螺菌和重生根瘤菌。尽管运动和趋化系统具有保守的核心，但根瘤菌具有多种修饰，可优化它们在土壤和根表面环境中的运动。土壤对微生物的流动性提出了独特的挑战，因为通过颗粒的水路并不总是连续的，尤其是在干燥的条件下。共生菌接种剂在田间环境中的有效性取决于它们在土壤中的流动性和扩散性，通常由水渗透或大型生物运动或网络辅助。因此，本综述总结了考虑和测试任何潜在接种剂的根瘤菌运动性和趋化性必不可少的因素。