Taerum Stephen J, Patel Ravikumar R, Alamo Justin E, Gage Daniel, Steven Blaire, Triplett Lindsay R
Department of Plant Pathology and Ecology, The Connecticut Agricultural Experiment Station, New Haven, Connecticut, USA.
Department of Molecular and Cell Biology, The University of Connecticut, Storrs, Connecticut, USA.
mSphere. 2025 May 27;10(5):e0003725. doi: 10.1128/msphere.00037-25. Epub 2025 Apr 30.
Soils contain diverse predatory protists that affect the abundance and behavior of rhizosphere bacteria, including bacteria that may benefit plant health. Protists harbor their own bacterial microbiomes, and we previously observed that plants inoculated with protists harbored rhizosphere bacteria similar to those in the protist inoculum. To determine how protist microbiomes affect the rhizosphere, we profiled the bacteria of eight diverse rhizosphere protist isolates after 2 years of laboratory culture. We then compared the protist culture microbiomes to maize rhizosphere communities 6 weeks after protist inoculation. Introduction of protists enriched 13 protist-associated bacterial amplicon sequence variants (ASVs) in the rhizosphere, which comprised ~10% of the rhizosphere bacterial community. Additional bacterial ASVs ranked highly in abundance in both rhizosphere (top 100) and protist (top 20) microbiomes; together, a median 47% of the protist microbiome was enriched or in high rank abundance in the rhizosphere. Inoculation with three out of eight protist cultures positively affected root biomass traits, but a protist mixture had no effect, indicating that the impact of protist-associated bacteria on plant growth is context dependent. Isolates of protist-associated bacteria had both positive and negative effects on protist growth in culture, suggesting that the bacteria use multiple strategies to survive in proximity to predators. This study demonstrates that even after long-term laboratory culture, rhizosphere protist cultures host bacteria that can colonize the rhizosphere of maize. The findings also identify diverse groups of rhizosphere-colonizing bacteria that persist among protist predators, which suggests that these bacteria could associate with or benefit from protists in the soil.
Understanding the impact of predatory protists on the plant microbiome will be essential to deploy protists in sustainable agriculture. This study shows that eight rhizosphere protist isolates hosted diverse and distinct bacterial communities and that a large proportion of these bacteria could be found colonizing the maize root environment 6 weeks after protists were inoculated onto seedlings. This study demonstrates that certain bacteria from the maize rhizosphere can persist for years in protist cultures and retain the ability to colonize rhizosphere soil, suggesting that protists might support the survival of these rhizosphere bacteria in the absence of the plant.
土壤中含有多种捕食性原生生物，它们会影响根际细菌的丰度和行为，包括可能有益于植物健康的细菌。原生生物拥有自己的细菌微生物群，我们之前观察到接种原生生物的植物所拥有的根际细菌与原生生物接种物中的细菌相似。为了确定原生生物微生物群如何影响根际，我们对经过两年实验室培养的八种不同根际原生生物分离株的细菌进行了分析。然后，我们将原生生物培养微生物群与原生生物接种6周后的玉米根际群落进行了比较。原生生物的引入使根际中13种与原生生物相关的细菌扩增子序列变体（ASV）得到富集，这些变体约占根际细菌群落的10%。其他细菌ASV在根际（前100名）和原生生物（前20名）微生物群中的丰度排名都很高；总体而言，原生生物微生物群中中位数为47%的细菌在根际中得到富集或丰度排名很高。接种八种原生生物培养物中的三种对根生物量性状有积极影响，但原生生物混合物没有影响，这表明与原生生物相关的细菌对植物生长的影响取决于具体情况。与原生生物相关的细菌分离株对培养中的原生生物生长既有积极影响也有消极影响，这表明细菌使用多种策略在捕食者附近生存。这项研究表明，即使经过长期实验室培养，根际原生生物培养物中的细菌仍能在玉米根际定殖。研究结果还确定了在原生生物捕食者中持续存在的不同根际定殖细菌群，这表明这些细菌可能与土壤中的原生生物相关或从原生生物中受益。
了解捕食性原生生物对植物微生物群的影响对于在可持续农业中应用原生生物至关重要。这项研究表明，八种根际原生生物分离株拥有多样且独特的细菌群落，并且在将原生生物接种到幼苗上6周后，可以发现这些细菌中有很大一部分在玉米根环境中定殖。这项研究表明，玉米根际的某些细菌可以在原生生物培养物中持续存在数年，并保留在根际土壤中定殖的能力，这表明原生生物可能在没有植物的情况下支持这些根际细菌的生存。
