The extraradical hyphae-associated microbiome of arbuscular mycorrhizal fungi (AMF), the “hyphosphere microbiome,” harbors a diverse reservoir of microbes. The biological interactions in the AMF hyphosphere have major implications for soil carbon and nutrient cycling, soil food web dynamics, and plant nutrition and health. Hyphosphere microbial communities are thought to assist AMF in accessing organic nutrients by degrading complex organic compounds that AMF are unable to do by themselves. The AMF, in return, provide an energy-rich microhabitat supplied with hyphal exudates that facilitates microbial growth and mobility in the hyphosphere. However, our current knowledge of hyphosphere entities, their trophic interactions and functional roles, and the underlying mechanisms facilitating microbial co-occurrence and co-operation is largely incomplete. Here, we review the current state of knowledge on the identity and putative roles of AMF hyphae-associated microbes, with a specific focus on prokaryotes, and potential drivers of such microbial communities in the hyphosphere. Moreover, we discuss the knowledge gaps and open challenges that should be addressed and prioritized in future studies on the AMF microbiomes. We also provide an appraisal of available and emerging tools and technologies and highlight the need for innovative approaches to disentangle AMF hyphosphere processes and answer the many unresolved questions.

丛枝菌根真菌 (AMF) 的根外菌丝相关微生物组，即“菌丝圈微生物组”，拥有多样化的微生物库。AMF 菌丝圈中的生物相互作用对土壤碳和养分循环、土壤食物网动态以及植物营养和健康具有重大影响。Hyphosphere 微生物群落被认为通过降解 AMF 自身无法完成的复杂有机化合物来帮助 AMF 获取有机养分。作为回报，AMF 提供了一个富含能量的微生境，其中提供了菌丝渗出物，促进了菌丝圈中微生物的生长和流动。然而，我们目前对菌丝圈实体、它们的营养相互作用和功能作用以及促进微生物共生和合作的潜在机制的了解在很大程度上是不完整的。在这里，我们回顾了关于 AMF 菌丝相关微生物的身份和推定作用的知识现状，特别关注原核生物，以及菌丝圈中此类微生物群落的潜在驱动因素。此外，我们讨论了未来 AMF 微生物组研究中应解决和优先考虑的知识差距和开放挑战。我们还提供了对可用和新兴工具和技术的评估，并强调需要创新方法来解开 AMF 菌丝圈过程并回答许多未解决的问题。我们讨论了在未来关于 AMF 微生物组的研究中应该解决和优先考虑的知识差距和开放挑战。我们还提供了对可用和新兴工具和技术的评估，并强调需要创新方法来解开 AMF 菌丝圈过程并回答许多未解决的问题。我们讨论了在未来关于 AMF 微生物组的研究中应该解决和优先考虑的知识差距和开放挑战。我们还提供了对可用和新兴工具和技术的评估，并强调需要创新方法来解开 AMF 菌丝圈过程并回答许多未解决的问题。