（1）Enterobacter species are plant growth-promoting rhizobacteria with the potential to enhance crop tolerance to abiotic stresses, but the molecular and physiological mechanisms remain incompletely understood. 肠杆菌属细菌是具有增强作物对非生物胁迫耐受性潜力的植物根际促生菌，但其分子和生理机制尚不完全清楚。

Salt-tolerant growth-promoting bacterium Enterobacter asburiae LL-1 isolated from rhizosphere soil of severely saline-alkali regions: Functional analysis of its genome and growth-promoting effect on maize under salt stress

摘要

（1）Enterobacter species are plant growth-promoting rhizobacteria with the potential to enhance crop tolerance to abiotic stresses, but the molecular and physiological mechanisms remain incompletely understood. 肠杆菌属细菌是具有增强作物对非生物胁迫耐受性潜力的植物根际促生菌，但其分子和生理机制尚不完全清楚。

（2） In this study, a salt-tolerant bacterial strain, Enterobacter asburiae LL-1, was isolated from the rhizosphere of maize grown in severely saline-alkali soil.本研究中，从生长在严重盐碱土壤中的玉米根际分离出一株耐盐细菌菌株——阿氏肠杆菌 LL-1。

（3）The strain exhibited multiple plant growth-promoting traits, including phosphorus solubilization, nitrogen fixation, and indole-3-acetic acid production, and showed exceptional salt tolerance (up to 1500 mM NaCl).该菌株表现出多种植物促生特性，包括解磷、固氮和产生吲哚-3-乙酸，并显示出卓越的耐盐性（高达 1500 mM NaCl）。

（4）Pot experiments demonstrated that LL-1 inoculation significantly alleviated salt-induced growth inhibition in maize, as evidenced by increased plant height, root length, root biomass, and leaf chlorophyll content. 盆栽实验证明，接种 LL-1 显著减轻了盐分诱导的玉米生长抑制，表现为株高、根长、根系生物量和叶片叶绿素含量增加。

（5） Furthermore, LL-1 inoculation reduced Na⁺ accumulation, enhanced K⁺ uptake, improved antioxidant enzyme activities (catalase and superoxide dismutase), and elevated proline levels, thereby mitigating oxidative damage. 此外，接种 LL-1 减少了 Na⁺积累，增强了 K⁺吸收，提高了抗氧化酶活性（过氧化氢酶和超氧化物歧化酶），并升高了脯氨酸水平，从而减轻了氧化损伤。

（6） At the molecular level, LL-1 upregulated the expression of maize antioxidant enzyme genes (ZmSOD4, ZmCAT2, ZmAPX2) and salt tolerance genes (ZmNHX1, ZmNHX2, ZmDREB2A). 在分子水平上，LL-1上调了玉米抗氧化酶基因（ZmSOD4、ZmCAT2、ZmAPX2）和耐盐基因（ZmNHX1、ZmNHX2、ZmDREB2A）的表达。

（7） Genome analysis identified multiple genes potentially involved in salt tolerance (such as nhaA, nhaB, maeN) and plant growth promotion. 基因组分析鉴定出多个可能参与耐盐（如 nhaA、nhaB、maeN）和植物促生的基因。

（8） These results indicate that E. asburiae LL-1 enhances maize salt tolerance through coordinated effects on ion homeostasis, antioxidant capacity, photosynthesis, and stress-responsive gene expression. 这些结果表明，阿氏肠杆菌 LL-1 通过对离子稳态、抗氧化能力、光合作用和胁迫响应基因表达的协同作用，增强了玉米的耐盐性。

（9） This study provides a promising microbial resource and correlative evidence for further mechanistic research on PGPR-mediated salt tolerance in crops. 本研究为深入探究植物根际促生菌介导的作物耐盐性机制提供了一个有前景的微生物资源和相关证据。

（10） Result

（11） E. asburiae LL-1 exhibits tolerance to high concentrations of NaCl stress E.asburiae LL-1表现出对高浓度NaCl胁迫的耐受性

（12） Genomic features and functional annotation of E.asburiae LL-1 strain菌株LL-1株的基因组特征和功能注释

（13） Genes associated with PGR and salt stress adaptation in E. asburiae strain LL-1 菌株LL-1株中与PGR和盐胁迫适应相关的基因

（14） Effects of LL-1 inoculation on the colonization and growth traits of maize seedlings under salt stress 菌株LL-1接种对盐胁迫下玉米幼苗定殖和生长性状的影响

（15） E. asburiae LL-1 regulates ion imbalance in maize under salt stress E.asburiae 菌株LL-1调节盐胁迫下玉米离子失衡

（16） Protective effects of the LL-1 strain on the photosynthetic system of maize seedlings under saline stress LL-1菌株对盐胁迫下玉米幼苗光合系统的保护作用

 LL-1 菌株对盐胁迫下玉米叶片活性氧水平和膜脂过氧化的缓解作用。核心结论是：LL-1 通过降低 H₂O₂ 和 O₂⁻ 等活性氧的积累，减少丙二醛含量和相对电导率，从而减轻盐胁迫引起的氧化损伤和细胞膜伤害。

（17） E. asburiae LL-1 reduces ROS accumulation in maize seedlings E.asburiae LL-1降低玉米幼苗活性氧积累

（18） E. asburiae LL-1 enhances antioxidant capacity in maize under salt stress

展示了 LL-1 菌株对盐胁迫下玉米幼苗抗氧化酶活性和脯氨酸含量的影响。核心结论是：LL-1 通过提高超氧化物歧化酶、过氧化物酶、过氧化氢酶、抗坏血酸过氧化物酶等抗氧化酶活性，并增加脯氨酸积累，增强玉米的抗氧化防御能力，从而缓解盐胁迫诱导的氧化损伤。

（19） E.asburiae LL-1 increases antioxidant capability by activating ROS-related genes in maize E.asburiae LL-1通过激活玉米ROS相关基因提高抗氧化能力

 这些结果表明，阿氏肠杆菌 LL-1 通过对离子稳态、抗氧化能力、光合作用和胁迫响应基因表达的协同作用，增强了玉米的耐盐性。