Data Sheet 3_Isolation and characterization of Stenotrophomonas rhizophila T3E: a multifunctional rhizobacterium enhancing tomato growth and soil health.xls

IntroductionPlant growth-promoting rhizobacteria (PGPR) serve as sustainable alternatives to chemical fertilizers and pesticides for improving crop productivity. Among them, Stenotrophomonas rhizophila has demonstrated considerable potential to enhance plant growth, yet the mechanisms underlying its effects on plant development and soil health remain insufficiently elucidated.
MethodsIn this study, S. rhizophila strain T3E was isolated and identified from the tomato (Solanum lycopersicum) rhizosphere based on morphological and phylogenetic analyses. The growth-promoting traits of T3E were comprehensively characterized through germination and pot experiments, integrated with phytohormone profiling, gene expression and biochemical analyses, soil assessment, and whole-genome sequencing.
ResultsInoculation with T3E significantly enhanced radicle length, primary root length, plant height, and seedling fresh weight, while quantitative assays revealed increased levels of indole-3-acetic acid (IAA) and abscisic acid (ABA) in the roots. qRT-PCR analysis showed that T3E upregulated multiple root growth-related genes (e.g., EAT2, LAX2, GTS1, GRFs) and T3E colonization-related genes (pyrB, flmH, pilR, bopD), supporting its strong root colonization ability. Physiologically, T3E treatment enhanced SOD activity, increased glycine betaine and soluble sugar levels, and reduced MDA content, suggesting improved root health and stress resistance. Whole-genome sequencing revealed a 4.31 Mb circular chromosome with 3,744 coding sequences, diverse secondary metabolite biosynthetic gene clusters, and abundant carbohydrate-active enzyme (CAZyme) genes. Soil assays demonstrated that T3E inoculation improved key physicochemical properties (TN, TP, TK, AK) and significantly enhanced the activities of soil enzymes, such as phosphatase, CAT, urease, and sucrase.
DiscussionThese findings identify S. rhizophila T3E as a promising multifunctional PGPR that promotes plant growth, strengthens rhizosphere colonization, and enhances soil fertility. This study provides a solid theoretical basis for developing microbial biofertilizers and advancing sustainable agricultural practices.

引言：植物促生根际细菌（plant growth-promoting rhizobacteria, PGPR）可作为化学肥料与农药的可持续替代方案，用以提升作物产量。其中，嗜根寡养单胞菌（Stenotrophomonas rhizophila）在促进植物生长方面展现出可观潜力，但其对植物生长发育与土壤健康的作用机制仍未得到充分阐释。
方法：本研究从番茄（Solanum lycopersicum）根际分离得到嗜根寡养单胞菌菌株T3E，并通过形态学与系统发育分析对其进行鉴定。本研究通过发芽试验、盆栽试验，结合植物激素谱分析、基因表达与生化分析、土壤评估以及全基因组测序，对T3E的促生特性进行了全面表征。
结果：接种T3E可显著提升胚根长度、主根长度、株高以及幼苗鲜重；定量检测结果显示，根系中的吲哚-3-乙酸（indole-3-acetic acid, IAA）与脱落酸（abscisic acid, ABA）水平显著升高。实时荧光定量PCR（qRT-PCR）分析表明，T3E可上调多个根系生长相关基因（如EAT2、LAX2、GTS1、GRFs）以及与T3E定殖相关的基因（pyrB、flmH、pilR、bopD），证实其具备较强的根系定殖能力。生理层面，T3E处理可提升超氧化物歧化酶（SOD）活性，增加甘氨酸甜菜碱与可溶性糖含量，并降低丙二醛（MDA）含量，提示其可改善根系健康状况并提升抗逆性。全基因组测序结果显示，该菌株包含一条4.31 Mb的环状染色体，编码3744个蛋白编码序列，拥有多样的次生代谢物生物合成基因簇以及丰富的碳水化合物活性酶（carbohydrate-active enzyme, CAZyme）基因。土壤评估实验表明，T3E接种可改善土壤关键理化性质（TN、TP、TK、AK），并显著提升土壤酶活性，包括磷酸酶、过氧化氢酶（CAT）、脲酶与蔗糖酶。
讨论：本研究结果表明，嗜根寡养单胞菌T3E是一款极具应用前景的多功能植物促生根际细菌，可促进植物生长、强化根际定殖并提升土壤肥力。本研究为微生物生物肥料的开发以及可持续农业实践的推进提供了坚实的理论基础。