The plant-microbe interactions, which is crucial for plant health and productivity, mainly occur in rhizosphere: a narrow zone of soil surrounding roots of living plants. The rhizosphere hosts one of the most intense habitats for microbial prey–predator interactions, especially between predatory protists and bacteria. Here, based on two key facts, microbial predators modulate rhizobacterial community composition, and the rhizobacterial community is the primary source of root microbiome, endophytes; we hypothesized that predation upon rhizobacteria would modulate the community composition of endophytic bacteria. The effects of three taxonomically distinct axenic protist species (Acanthamoeba castellanii, Vermamoeba vermiformis, and Heteromita globosa) were tested in this study. To examine the robustness of the hypotheses, the experiments were conducted in three soil types characterized by distinct bacterial communities and physicochemical properties. The bacterial community compositions were analyzed with high throughput sequencing. Bacterial gene abundances were estimated with a real-time-PCR method. The results showed that protists modulated endophytic communities, which originated in the rhizosphere soil. The modulation of endophytic communities by protists showed chaotic patterns rather than a deterministic effect under different soil types. The observed chaotic dynamics were further confirmed with an additional experiment, in which chaos was triggered by changes in the dilution rates of soil nutrients. Furthermore, the presence of predators enhanced the root colonization of endophytes. Our findings identify a key mechanism for the modulation of root endophytes and enhance understanding of underground plant-microbe interactions, which can lead to open new avenues for modulating the root microbiome to enhance crop production.

中文翻译：

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根际原生生物对内生菌的营养调节


植物与微生物的相互作用对植物健康和生产力至关重要，主要发生在根际：围绕活植物根部的狭窄土壤区域。根际是微生物猎物与捕食者相互作用最密集的栖息地之一，尤其是在捕食性原生生物和细菌之间。在这里，基于两个关键事实，微生物捕食者调节根际细菌群落组成，而根际细菌群落是根系微生物组、内生菌的主要来源;我们假设对根际细菌的捕食会调节内生细菌的群落组成。本研究测试了三种分类学上不同的轴生原生生物物种 （Acanthamoeba castellanii、Vermamoeba vermiformis 和 Heteromita globosa） 的影响。为了检验假设的稳健性，在三种土壤类型中进行了实验，这些土壤类型具有不同的细菌群落和物理化学特性。用高通量测序分析细菌群落组成。用实时 PCR 方法估计细菌基因丰度。结果表明，原生生物调节起源于根际土壤的内生菌群落。原生生物对内生菌群落的调节在不同土壤类型下表现出混沌模式，而不是确定性效应。观察到的混沌动力学通过一项额外的实验进一步证实，其中混沌是由土壤养分稀释率的变化引发的。此外，捕食者的存在增强了内生菌的根定植。 我们的研究结果确定了调节根内生菌的关键机制，并增强了对地下植物-微生物相互作用的理解，这可以为调节根系微生物组以提高作物生产开辟新的途径。