一株低温胁迫下促玉米生长的萎缩芽孢杆菌NLHLT2的生物活性分析

Bacillus atrophaeus NLHLT2 promotes maize growth under low-temperature stress

摘要:

【背景】 青藏高原的极端生境蕴藏着具有特殊生物活性的微生物资源。【目的】 探究青藏高原萎缩芽孢杆菌(Bacillus atrophaeus) NLHLT2对玉米(Zea mays)的促生效应。【方法】 通过生物活性检测、全基因组测序及基因功能分析，解析其生物活性及相关功能基因；制备2×10⁸ CFU/mL菌悬液，按100、150、200、250、300倍梯度稀释筛选最适浓度，在低温条件下以最适浓度菌悬液对玉米幼苗进行灌根，测定其对玉米生长的影响。【结果】 菌株NLHLT2对植物病原真菌禾谷镰刀菌(Fusarium graminearum)、稻黑孢菌(Nigrospora oryzae)表现出显著的拮抗活性，并且菌株NLHLT2具备产铁载体、赤霉素(gibberellins, GA)、细胞分裂素(cytokinin, CTK)能力，具有耐盐及耐低温性；低温条件下，菌株NLHLT2菌悬液(1×10⁶ CFU/mL)灌根显著提高了玉米株高、根长、叶面积、生物量、超氧化物歧化酶(superoxide dismutase, SOD)活性、过氧化物酶(peroxidase, POD)活性及脯氨酸(proline, Pro)含量，同时显著降低玉米幼苗丙二醛(malondialdehyde, MDA)含量，有效增强玉米幼苗对低温环境的生理适应能力；获得菌株NLHLT2完整基因组序列，长度为4 212 529 bp，G+C含量43.29%，并且菌株基因组编码了与促生及逆境应答相关的功能基因。【结论】 本研究结合菌株NLHLT2的生物活性与基因组特征，分析促生及耐逆相关基因，揭示其在低温条件下与玉米的相互作用机制，为玉米在高原的生长提供优良菌源及理论依据。

Abstract:

[Background] The extreme environments of Qinghai-Xizang Plateau harbor unique microbial resources with special biological activities. [Objective] To investigate the maize (Zea mays) growth-promoting effect of Bacillus atrophaeus NLHLT2 isolated from Qinghai-Xizang Plateau. [Methods] We employed bioactivity assays, whole-genome sequencing, and gene function analysis to characterize the bioactivity and related functional genes of the strain. The bacterial suspension with a concentration of 2×10⁸ CFU/mL was prepared and diluted in gradients of 100, 150, 200, 250, and 300 folds, and the optimal concentration for promoting plant growth was determined. Under low-temperature conditions, maize seedlings were treated with the strain suspension at the optimal concentration via root irrigation, and the effect of the suspension on maize growth was evaluated. [Results] Strain NLHLT2 exhibited significant antagonistic activities against plant pathogenic fungi Fusarium graminearum and Nigrospora oryzae. Meanwhile, the strain possessed the abilities to produce siderophores, gibberellins, and cytokinins and both salt and low-temperature tolerance. Under low-temperature conditions, root irrigation with the strain suspension (1×10⁶ CFU/mL) significantly enhanced the plant height, root length, leaf area, biomass, superoxide dismutase activity, peroxidase activity, and proline content, while markedly reducing the malondialdehyde content in maize seedlings. These effects collectively improved the physiological adaptability of maize seedlings to low-temperature stress. The complete genome sequence of strain NLHLT2 was 4 212 529 bp, with the G+C content of 43.29%. The genome contained functional genes associated with plant growth promotion and stress responses. [Conclusion] By studying the biological activity and genomic characteristics of strain NLHLT2, we analyze the genes related to growth promotion and stress tolerance, aiming to reveal the interaction mechanism between the strain and maize under low-temperature conditions. This study provides an elite strain and a theoretical basis for maize growth in high-altitude regions.