Plant performance is impacted by rhizosphere bacteria. These bacteria are subjected to both bottom-up control by root exudates as well as top-down control by predators, particularly protists. Protists stimulate plant growth-promoting microbes resulting in improved plant performance. However, knowledge of the mechanisms that determine the interconnections within such tripartite protist–bacteria–plant interactions remains limited. We conducted experiments examining the effects of different densities of the predatory protist Cercomonas lenta on rhizosphere bacterial communities, specifically zooming on interactions between Cercomonas lenta and key bacterial taxa, as well as interactions among key bacterial taxa. We tracked rhizosphere bacterial community composition, potential microbial interactions, and plant performance. We found that Cercomonas lenta inoculation led to an average increase in plant biomass of 92.0%. This effect was linked to an increase in plant growth-promoting rhizobacteria (Pseudomonas and Sphingomonas) and a decrease in bacteria (Chitinophaga) that negatively impact on plant growth-promoting rhizobacteria. We also found evidence for cooperative enhancements in biofilm formation within the plant growth-promoting rhizobacterial consortium. Cercomonas lenta enhanced a plant growth-promoting rhizobacterial consortium colonization by promoting its cooperative biofilm formation in the rhizosphere, leading to a 14.5% increase in phosphate solubilization that benefits plant growth. Taken together, we provide mechanistic insights into how the predatory protist Cercomonas lenta impacts plant growth, namely by stimulating plant beneficial microbes and enhancing their interactive activities such as biofilm formation. Predatory protists may therefore represent promising biological agents that can contribute to sustainable agricultural practices by promoting interactions between the plant and its microbiome.

中文翻译：

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捕食性原生生物通过促进植物生长的根际细菌联盟来影响植物性能


植物性能受根际细菌的影响。这些细菌既受到根系分泌物的自下而上的控制，也受到捕食者（尤其是原生生物）的自上而下的控制。原生生物刺激植物生长促进微生物，从而提高植物性能。然而，关于决定这种三方原生生物-细菌-植物相互作用中相互联系的机制的知识仍然有限。我们进行了实验，研究了不同密度的捕食性原生生物 Cercomonas lenta 对根际细菌群落的影响，特别是放大了 Cercomonas lenta 与关键细菌分类群之间的相互作用，以及关键细菌分类群之间的相互作用。我们跟踪了根际细菌群落组成、潜在的微生物相互作用和植物性能。我们发现 Cercomonas lenta 接种导致植物生物量平均增加 92.0%。这种效应与植物生长促进根际细菌（假单胞菌和鞘氨醇）的增加和细菌（几丁质噬菌）的减少有关，这些细菌对植物生长促进根际细菌产生负面影响。我们还发现了在植物生长促进根际细菌联盟内合作增强生物膜形成的证据。Cercomonas lenta 通过促进其在根际的合作生物膜形成来增强促进植物生长的根际细菌联盟定植，导致磷酸盐溶解度增加 14.5%，有利于植物生长。综上所述，我们提供了关于捕食性原生生物 Cercomonas lenta 如何影响植物生长的机制见解，即通过刺激植物有益微生物并增强它们的互动活动，例如生物膜的形成。 因此，捕食性原生生物可能代表有前途的生物制剂，可以通过促进植物与其微生物组之间的相互作用来促进可持续农业实践。