Arbuscular mycorrhizal (AM) fungal structures, such as spores, vesicles, extra- and intra- radical hyphae, are home to diverse communities of prokaryotic (bacterial and archaeal) taxa and can have significant impact on the movement and behavior of those microbes within the soil. The ability to disperse via fungal hyphae, known as the fungal highway effect, was first observed in ectomycorrhiza and later in other fungal groups. This effect may benefit soil prokaryotes allowing them to explore new microhabitats in soil, offering advantages such as improved nutrient access, enhanced dispersal and colonization. Although the term “fungal highways” is well established, there still are only few studies that address the partner interactions and movement of microorganisms through the hyphal networks when referring to AM fungi. Bacteria can colonize the surfaces of hyphae and form biofilms that provide protection for both the bacteria and the fungus, influence the nutrient cycles, giving the bacteria access to resources transported by the fungus. Bacteria movement on AM fungal hyphae is facilitated by several mechanisms, including physical transport along the hyphal networks, swimming within the continuous water films that develop along the hyphal surfaces, and chemotaxis, where the bacteria move towards or away from specific chemical signals. Overall, the interactions between bacteria and AM fungi appears as a dynamic and complex process. Yet, we still do not know much about the influence of soil properties, plant age and species, seasonality, soil management and different climate with respect to AM fungal highways and microbiomes. Here, we review the current knowledge on prokaryotic movement through AM fungal hyphosphere and the possible factors that could affect it. Future research needs to elucidate mechanisms involved in the recruitment and/or migration of microbes in the AM fungal hyphosphere. Understanding these interactions may eventually help developing more sustainable agricultural practices and/or support environmental conservation.

中文翻译：

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丛枝菌根真菌高速公路 – 什么、如何以及为什么？


丛枝菌根 （AM） 真菌结构，如孢子、囊泡、根外和根内菌丝，是不同原核（细菌和古细菌）分类群群落的家园，可对这些微生物在土壤中的运动和行为产生重大影响。通过真菌菌丝传播的能力，称为真菌公路效应，首先在外生菌根中观察到，后来在其他真菌组中观察到。这种效应可能使土壤原核生物受益，使它们能够在土壤中探索新的微生境，从而提供改善养分获取、增强扩散和定植等优势。尽管 “真菌高速公路 ”一词已经得到广泛认可，但在提到 AM 真菌时，仍然只有少数研究涉及微生物通过菌丝网络的伴侣相互作用和移动。细菌可以在菌丝表面定植并形成生物膜，为细菌和真菌提供保护，影响营养循环，使细菌能够获得真菌运输的资源。细菌在 AM 真菌菌丝上的移动由多种机制促进，包括沿菌丝网络的物理运输、在沿菌丝表面形成的连续水膜内游泳以及趋化性，即细菌靠近或远离特定的化学信号。总体而言，细菌和 AM 真菌之间的相互作用是一个动态而复杂的过程。然而，我们仍然不太了解土壤特性、植物年龄和物种、季节性、土壤管理和不同气候对增材制造真菌高速公路和微生物组的影响。在这里，我们回顾了目前关于 AM 真菌 hyphosphere 的原核生物运动以及可能影响它的可能因素。 未来的研究需要阐明 AM 真菌菌圈中微生物募集和/或迁移所涉及的机制。了解这些相互作用最终可能有助于发展更可持续的农业实践和/或支持环境保护。