Trophic interactions in microbiomes influence plant host population size and ecosystem function

Plant microbiomes that comprise diverse microorganisms, including prokaryotes, eukaryotes, and viruses, are the key determinant of plant population dynamics and ecosystem function. Despite their importance, little is known about how interactions, especially trophic interactions, between microbes from different domains modify the importance of microbiomes for plant hosts and ecosystems. Using the common duckweed Lemna minor, we experimentally examined the effects of predation (by bacterivorous protists) and parasitism (by bacteriophages) within microbiomes on plant population size and ecosystem phosphorus removal. Our results revealed that the addition of predators increased plant population size and phosphorus removal whereas the addition of parasites showed the opposite pattern. The structural equation modeling further pointed out that predation and parasitism affected plant population size and ecosystem function via distinct mechanisms that were both mediated by microbiomes. Our results highlight the importance of understanding microbial trophic interactions for predicting the outcomes and ecosystem impacts of plant-microbiome symbiosis.

由原核生物（prokaryotes）、真核生物（eukaryotes）与病毒（viruses）等多样微生物构成的植物微生物组（plant microbiome），是调控植物种群动态与生态系统功能的核心决定因素。尽管其重要性不言而喻，但学界对于不同生物域微生物间的相互作用——尤其是营养相互作用（trophic interactions）——如何改变微生物组对植物宿主与生态系统的贡献，仍知之甚少。本研究以常见的小浮萍（Lemna minor）为实验材料，探究了微生物组内食细菌原生生物（bacterivorous protists）介导的捕食作用，以及噬菌体（bacteriophages）介导的寄生作用，对植物种群规模与生态系统除磷效率的影响。研究结果显示，添加捕食者可提升植物种群规模与除磷效率，而添加寄生者则呈现出相反的变化趋势。结构方程模型（structural equation modeling）进一步揭示，捕食作用与寄生作用通过两条截然不同的路径影响植物种群规模与生态系统功能，且二者均由微生物组介导调控。本研究结果凸显了解析微生物营养相互作用的重要性，这可为预测植物-微生物组共生关系的作用结果及其生态系统效应提供理论支撑。