DBT-North East Centre for Agricultural Biotechnology, Jorhat, Assam, 785013, India.
Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat, Assam, 785013, India.
Arch Microbiol. 2022 Jan 7;204(2):124. doi: 10.1007/s00203-021-02741-5.
Soil pH conditions have important consequences for microbial community structure, their dynamics, ecosystem processes, and interactions with plants. Low soil pH affects the growth and functional activity of bacterial biocontrol agents which may experience a paradigm shift in their ability to act antagonistically against fungal phytopathogens. In this study, the antifungal activity of an acid-tolerant soil bacterium Bacillus amyloliquefaciens MBNC was evaluated under low pH and compared to its activity in neutral pH conditions. Bacterial supernatant from 3-day-old culture (approximately 11.2 × 10 cells/mL) grown in low pH conditions was found more effective against fungal pathogens. B. amyloliquefaciens MBNC harboured genes involved in the synthesis of secondary metabolites of which surfactin homologues, with varying chain length (C11-C15), were identified through High-Resolution Mass Spectroscopy. The pH of the medium influenced the production of these metabolites. Surfactin C15 was exclusive to the extract of pH 4.5; production of iturinA and surfactin C11 was detected only in pH 7.0, while surfactin C12, C13 and C14 were detected in extracts of both the pH conditions. The secretion of phytohormones viz. indole acetic acid and gibberellic acid by B. amyloliquefaciens MBNC was detected in higher amounts in neutral condition compared to acidic condition. Although, secretion of metabolites and phytohormones in B. amyloliquefaciens MBNC was influenced by the pH condition of the medium, the isolate retained its antagonistic efficiency against several fungal phyto-pathogens under acidic condition.
土壤 pH 值条件对微生物群落结构、动态、生态系统过程以及与植物的相互作用具有重要影响。低土壤 pH 值会影响细菌生防剂的生长和功能活性，它们可能会在拮抗真菌植物病原菌的能力上发生范式转变。在这项研究中，评估了耐酸土壤细菌解淀粉芽孢杆菌 MBNC 在低 pH 值条件下的抗真菌活性，并将其与中性 pH 值条件下的活性进行了比较。在低 pH 值条件下生长的 3 天龄培养物（约 11.2×10 个细胞/mL）的细菌上清液被发现对真菌病原体更有效。解淀粉芽孢杆菌 MBNC 携带参与合成次生代谢物的基因，其中通过高分辨率质谱鉴定出了不同链长（C11-C15）的表面活性剂类似物。培养基的 pH 值影响这些代谢物的产生。表面活性剂 C15 仅存在于 pH 4.5 的提取物中；仅在 pH 7.0 时检测到iturinA 和表面活性剂 C11 的产生，而表面活性剂 C12、C13 和 C14 则存在于两种 pH 条件下的提取物中。解淀粉芽孢杆菌 MBNC 分泌的植物激素，如吲哚乙酸和赤霉素，在中性条件下的分泌量明显高于酸性条件下。尽管代谢物和植物激素的分泌在解淀粉芽孢杆菌 MBNC 中受培养基 pH 值条件的影响，但该分离株在酸性条件下仍保持对几种真菌植物病原菌的拮抗效率。
