Department of Biology, University of Oxford, Oxford OX1 3RB, United Kingdom.
ISME J. 2024 Jan 8;18(1). doi: 10.1093/ismejo/wrae072.
Bacterial persistence in the rhizosphere and colonization of root niches are critical for the establishment of many beneficial plant-bacteria interactions including those between Rhizobium leguminosarum and its host legumes. Despite this, most studies on R. leguminosarum have focused on its symbiotic lifestyle as an endosymbiont in root nodules. Here, we use random barcode transposon sequencing to assay gene contributions of R. leguminosarum during competitive growth in the rhizosphere and colonization of various plant species. This facilitated the identification of 189 genes commonly required for growth in diverse plant rhizospheres, mutation of 111 of which also affected subsequent root colonization (rhizosphere progressive), and a further 119 genes necessary for colonization. Common determinants reveal a need to synthesize essential compounds (amino acids, ribonucleotides, and cofactors), adapt metabolic function, respond to external stimuli, and withstand various stresses (such as changes in osmolarity). Additionally, chemotaxis and flagella-mediated motility are prerequisites for root colonization. Many genes showed plant-specific dependencies highlighting significant adaptation to different plant species. This work provides a greater understanding of factors promoting rhizosphere fitness and root colonization in plant-beneficial bacteria, facilitating their exploitation for agricultural benefit.
在根际中细菌的持续存在和根栖 niche 的定殖对于许多有益的植物-细菌相互作用的建立至关重要，包括根瘤菌与宿主豆科植物之间的相互作用。尽管如此，大多数关于根瘤菌的研究都集中在其作为根瘤内生菌的共生生活方式上。在这里，我们使用随机条形码转座子测序来检测根瘤菌在根际竞争生长和定殖各种植物物种过程中的基因贡献。这有助于鉴定 189 个在不同植物根际中生长普遍需要的基因，其中 111 个基因突变也影响随后的根定殖（根际渐进），还有 119 个基因是定殖所必需的。共同的决定因素表明需要合成必需的化合物（氨基酸、核苷酸和辅因子），适应代谢功能，对外界刺激做出反应，并承受各种压力（如渗透压的变化）。此外，趋化性和鞭毛介导的运动是根定殖的前提条件。许多基因表现出植物特异性的依赖性，这突出了对不同植物物种的显著适应。这项工作提供了对促进植物有益细菌根际适应性和根定殖的因素的更好理解，有助于为农业效益而利用这些因素。
