Department of Industrial and Environmental Microbiology, Institute of Biological Sciences, Maria Curie-Skłodowska University, 19 Akademicka, 20-033 Lublin, Poland.
Department of Natural Environment Biogeochemistry, Institute of Agrophysics, Polish Academy of Sciences, 4 Doświadczalna, 20-290 Lublin, Poland.
Sci Total Environ. 2024 Nov 15;951:175554. doi: 10.1016/j.scitotenv.2024.175554. Epub 2024 Aug 14.
Legume-rhizobial symbiosis plays an important role in agriculture and ecological restoration. This process occurs within special new structures, called nodules, formed mainly on legume roots. Soil bacteria, commonly known as rhizobia, fix atmospheric dinitrogen, converting it into a form that can be assimilated by plants. Various environmental factors, including a low temperature, have an impact on the symbiotic efficiency. Nevertheless, the effect of temperature on the phenotypic and symbiotic traits of rhizobia has not been determined in detail to date. Therefore, in this study, the influence of temperature on different cell surface and symbiotic properties of rhizobia was estimated. In total, 31 Rhizobium leguminosarum sv. trifolii strains isolated from root nodules of red clover plants growing in the subpolar and temperate climate regions, which essentially differ in year and day temperature profiles, were chosen for this analysis. Our results showed that temperature has a significant effect on several surface properties of rhizobial cells, such as hydrophobicity, aggregation, and motility. Low temperature also stimulated EPS synthesis and biofilm formation in R. leguminosarum sv. trifolii. This extracellular polysaccharide is known to play an important protective role against different environmental stresses. The strains produced large amounts of EPS under tested temperature conditions that facilitated adherence of rhizobial cells to different surfaces. The high adaptability of these strains to cold stress was also confirmed during symbiosis. Irrespective of their climatic origin, the strains proved to be highly effective in attachment to legume roots and were efficient microsymbionts of clover plants. However, some diversity in the response to low temperature stress was found among the strains. Among them, M16 and R137 proved to be highly competitive and efficient in nodule occupancy and biomass production; thus, they can be potential yield-enhancing inoculants of legumes.
豆科植物-根瘤菌共生在农业和生态恢复中起着重要作用。这个过程发生在特殊的新结构中，称为根瘤，主要在豆科植物的根部形成。土壤中的细菌，通常被称为根瘤菌，固定大气中的氮气，将其转化为植物可以吸收的形式。各种环境因素，包括低温，都会影响共生效率。然而，迄今为止，温度对根瘤菌表型和共生特性的影响还没有被详细确定。因此，在这项研究中，我们估计了温度对根瘤菌不同细胞表面和共生特性的影响。总共有 31 株根瘤菌分离自生长在亚极地和温带气候区的红三叶草根瘤，这些根瘤菌在年和日温度曲线方面存在显著差异。我们的研究结果表明，温度对根瘤菌细胞的几个表面特性有显著影响，如疏水性、聚集性和运动性。低温还刺激了 R. leguminosarum sv. trifolii 中 EPS 的合成和生物膜的形成。这种胞外多糖已知在抵御各种环境胁迫方面起着重要的保护作用。在测试的温度条件下，这些菌株产生大量的 EPS，这有助于根瘤菌细胞附着在不同的表面上。这些菌株对冷应激的高度适应性也在共生过程中得到了证实。无论其气候起源如何，这些菌株在与豆科植物根部的附着以及作为三叶草植物的有效微共生体方面都表现出高度的有效性。然而，在对低温胁迫的反应中，我们发现菌株之间存在一定的多样性。在这些菌株中，M16 和 R137 被证明在占据和生物量产生方面具有高度的竞争力和效率；因此，它们可能是豆科植物增产的潜在接种剂。
