Abstract

We explored the membrane lipid and fatty acid composition and plant growth–promoting (PGP) mechanisms of two bacterial endophytes, Bacillus sp. E25 and Bacillus sp. CR71, under saline stress, that is known to be a major detriment to crop yield. Effect of single and co-inoculation of the strains on root and shoot lengths, relative chlorophyll content, and plant biomass in tomato plants (Lycopersicon esculentum cv Saladette) grown in greenhouses was also evaluated. Our results show that single and co-inoculated tomato plants with bacilli strains E25 and CR71, growing under normal or saline stress conditions (100 and 200 mM NaCl), exhibited an increase in root and shoot lengths, chlorophyll content, and biomass parameters, compared with control plants (uninoculated). Additionally, these bacilli strains were antagonistic toward fungal pathogens Fusarium oxysporum and (to a greater extent) Botrytis cinerea in the presence or absence of NaCl. Interestingly, both endophytes maintained good PGP activities, producing compounds like indole-3-acetic acid (IAA), proteases, siderophores, and biofilm. Saline conditions led to changes in membrane phospholipid and fatty acid levels in both. Phosphatidylethanolamine biosynthesis and branched (16:1^∆9; 17:0i) and unsaturated fatty acids increased in E25; CR71 showed increase in relative amounts of the same fatty acids and accumulated an unidentified lipid. Bacillus strains E25 and CR71 differentially modify their membrane phospholipid composition as a protective mechanism, potentially for maintaining PGP activities, under saline stress.

中文翻译：

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盐胁迫下抗真菌和促进植物生长的芽孢杆菌改变其膜组成

摘要

我们探索了两种细菌内生细菌芽孢杆菌属的膜脂和脂肪酸组成以及植物促生长（PGP）的机制。E25和芽孢杆菌属。众所周知，CR71在盐胁迫下会严重损害作物的产量。单一和共同接种菌株对番茄植株根和茎长，相对叶绿素含量和植物生物量的影响（番茄）还评估了在温室中生长的cv Saladette）。我们的结果表明，与普通和盐胁迫条件下（100和200 mM NaCl）生长的带有杆菌菌株E25和CR71的单株和共接种番茄植株相比，根和茎长，叶绿素含量和生物量参数均增加了对照植物（未接种）。此外，这些细菌菌株对真菌病原菌镰刀菌和（更大程度上）灰葡萄孢具有拮抗作用。在存在或不存在氯化钠的情况下。有趣的是，两种内生菌均保持良好的PGP活性，产生吲哚-3-乙酸（IAA），蛋白酶，铁载体和生物膜等化合物。盐水条件导致两者中膜磷脂和脂肪酸水平的变化。E25中磷脂酰乙醇胺的生物合成和分支（16：1 ^∆9； 17：0i）和不饱和脂肪酸增加；CR71显示相同脂肪酸的相对含量增加，并且积累了未确定的脂质。芽孢杆菌菌株E25和CR71差异性地修饰了它们的膜磷脂组成，作为一种保护机制，可能在盐胁迫下维持PGP的活性。