Endophytic bacterial diversity of <i>Avicennia marina</i> helps to confer resistance against salinity stress in <i>Solanum lycopersicum</i>

The current study aimed to explore the endophytic bacterial diversity of <i>Avicennia marina</i> and the potential roles of these endophytes in counteracting saline conditions in tomato plants. Molecular analysis revealed strains from <i>Paenibacillus, Bacillus, Microbacterium</i>, <i>Citrobacter</i>, <i>Lysinibacillus, Halomonas, Virgibacillus</i>, <i>Exiguobacterium</i>, and <i>Vibrio</i>. However, <i>Bacillus pumilus</i> AM11 and <i>Exiguobacterium</i> sp<i>.</i> AM25 showed significantly higher growth in saline media. In response to salinity stress, tomato plants treated with AM11 and AM25 showed significantly higher (∼15–23%) biomass, photosynthetic rate and pigment accumulation compared to controls. Salinity-exposed plants had significantly reduced growth and increased (three-fold) lipid peroxidation, whilst glutathione, catalase, and peroxidase activities were significantly reduced. In contrast, AM11, AM25, and methionine improved these physiochemical attributes. The study concludes that the application of bacterial endophytes from plants growing in saline conditions can offer other plants similar stress-resistance potential. Such halophytic bacterial strains can be used to improve plant growth in saline conditions.

本研究旨在探究白骨壤（*Avicennia marina*）的内生细菌（endophytic bacteria）多样性，以及这些内生菌在缓解番茄植株盐胁迫（salinity stress）中的潜在作用。分子生物学分析显示，分离得到的菌株隶属于类芽孢杆菌属（*Paenibacillus*）、芽孢杆菌属（*Bacillus*）、微杆菌属（*Microbacterium*）、柠檬酸杆菌属（*Citrobacter*）、赖氨酸芽孢杆菌属（*Lysinibacillus*）、盐单胞菌属（*Halomonas*）、维尔吉芽孢杆菌属（*Virgibacillus*）、微小杆菌属（*Exiguobacterium*）与弧菌属（*Vibrio*）。然而，短小芽孢杆菌（*Bacillus pumilus*）AM11与微小杆菌属（*Exiguobacterium* sp.）AM25在含盐培养基中展现出显著更优的生长性能。在盐胁迫条件下，经AM11与AM25处理的番茄植株，其生物量、光合速率与色素积累量较对照组显著提升约15%~23%。仅暴露于盐胁迫的植株生长显著受抑，脂质过氧化（lipid peroxidation）水平升高至对照组的3倍，同时谷胱甘肽（glutathione）、过氧化氢酶（catalase）与过氧化物酶（peroxidase）的活性显著降低。与之相反，经AM11、AM25与甲硫氨酸处理后，上述生理生化特性（physiochemical attributes）均得到改善。本研究得出结论：从盐生植物中分离的内生细菌菌株，可赋予其他植物类似的抗逆潜力；此类嗜盐细菌菌株可用于提升盐渍环境下的植株生长性能。