Soil salinization is considered a serious agricultural problem that affects the growth and yield of plants in the world. Poly-γ-glutamic acid (γ-PGA) can adsorb cations and increase plant salt tolerance. However, the role of γ-PGA-producing bacteria in regulating plant salt stress response and the involved mechanisms remain unknown. This study characterized the effects of plant growth-promoting and γ-PGA-producing strain W25 on the growth and salt stress response in lettuce, and the microbial composition and structure in rhizosphere soil. This strain tolerated up to 8% NaCl and showed K solubilization and γ-PGA production in salt setress. Strain W25 significantly decreased the concentration of water-soluble Na in solution and the Na high storing capability of γ-PGA produced by strain W25 was 27.48 mg g. Inoculation with strain W25 could improve lettuce biomass production by decreasing the plant Na/K and Na/Ca ratios, improving the plant antioxidant levels, and regulating the plant IAA level. Strain W25 inoculation enhanced soil quality by reducing soil exchangeable sodium percentage, and increasing available K and P and soil enzyme activities. Furthermore, inoculation with strain W25 not only increased the diversities but also changed the compositions of bacterial and fungal communities in the lettuce rhizosphere soils. The abundances of beneficial soil bacteria, such as , , and , were enhanced, which showed significantly positive correlations with the biomass of lettuce. While the abundances of plant pathogenic fungal genera like and were decreased in strain W25 inoculated rhizosphere soils. This study showed the great potential of γ-PGA-producing PGPB for the enhancement of plant growth in salt-affected soil.

中文翻译：

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产聚γ-谷氨酸细菌解淀粉芽孢杆菌W25通过调节生理生化过程和影响根际土壤微生物群落增强生菜耐盐性

土壤盐碱化被认为是影响世界植物生长和产量的严重农业问题。聚γ-谷氨酸（γ-PGA）可以吸附阳离子，提高植物的耐盐性。然而，γ-PGA产生菌在调节植物盐胁迫反应中的作用及其机制仍不清楚。本研究表征了植物促生长和产生 γ-PGA 的菌株 W25 对生菜生长和盐胁迫响应以及根际土壤微生物组成和结构的影响。该菌株耐受高达 8% 的 NaCl，并在盐胁迫下表现出 K 溶解和 γ-PGA 生成。菌株W25显着降低了溶液中水溶性Na的浓度，菌株W25产生的γ-PGA的Na高储存能力为27.48 mg·g。接种菌株W25可以通过降低植物Na/K和Na/Ca比、提高植物抗氧化水平、调节植物IAA水平来提高生菜生物量产量。菌株 W25 接种通过降低土壤交换性钠百分比、增加有效钾和有效磷以及土壤酶活性来提高土壤质量。此外，接种菌株W25不仅增加了多样性，而且改变了生菜根际土壤中细菌和真菌群落的组成。 、 、 、 等土壤有益细菌丰度增强，与生菜生物量呈显着正相关。而在接种菌株W25的根际土壤中，植物病原真菌如和的丰度降低。这项研究表明，产生 γ-PGA 的 PGPB 在促进受盐影响的土壤中植物生长方面具有巨大潜力。