Abstract Many processes of crucial ecological, interactive and productive importance take place between plants and microorganisms in the rhizosphere, the portion of soil closest to plant roots. Yet, little is known about the establishment, succession and functions of bacterial communities in the rhizosphere which are dependent on the development of biofilm structures. This work used physiological and molecular characterization to study changes in bacterial biofilm communities in the rhizosphere of alfalfa (Medicago sativa L.). We evaluated natural biofilm-like structures and the early succession of artificial biofilm-like structures associated to rhizospheric soil by building a simplified community with bacterial strains isolated from artificial surfaces under laboratory conditions. Comparing the artificial succession assay with natural rhizospheric soil, results showed altered bacterial counts, biofilm-forming abilities and community structures at different time points. Highly adhesive strains belonging to γ-proteobacteria dominated the initial stages of biofilm development associated to roots, whereas α-proteobacteria and Actinobacteria prevailed in naturally established mature biofilms in the rhizosphere. Adhesion assays on the roots showed changes in the structure and dynamics of the bacterial community after short experimentation times, which correlated quite well with the results obtained on artificial surfaces. Summing up, the study found that the establishment of multibacterial communities in the rhizosphere of alfalfa is a dynamic process which probably includes the initial formation of biofilm-like structures by highly-adherent strains and the subsequent shaping towards a mature community through mechanisms of replacement and co-existence.

中文翻译：

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与苜蓿根际生物膜样结构相关的细菌群落的早期演替

摘要 许多具有重要生态、互动和生产重要性的过程发生在根际中的植物和微生物之间，根际是最靠近植物根部的土壤部分。然而，人们对依赖于生物膜结构发展的根际细菌群落的建立、演替和功能知之甚少。这项工作使用生理和分子特征来研究苜蓿 (Medicago sativa L.) 根际细菌生物膜群落的变化。我们通过在实验室条件下从人工表面分离的细菌菌株建立一个简化的群落，评估了天然生物膜样结构和与根际土壤相关的人工生物膜样结构的早期演替。将人工演替试验与天然根际土壤进行比较，结果显示不同时间点的细菌数量、生物膜形成能力和群落结构发生了变化。属于γ-变形菌的高度粘附菌株主导了与根相关的生物膜发育的初始阶段，而α-变形菌和放线菌在根际自然建立的成熟生物膜中占主导地位。根部的粘附试验表明，在短实验时间后，细菌群落的结构和动力学发生了变化，这与在人造表面上获得的结果非常相关。加起来，