Resistance mechanisms of acid Mn2+-resistant purple nonsulfur bacteria (PNSB) were investigated to determine their ability to alleviate adverse effects of excess manganese on plant growth and productivity in acid sulfate soils (ASS). PNSB were isolated and selected based on their resistance to acid and manganese. Their resistance mechanisms were assessed on the basis of biosorption, bioaccumulation, and plant growth promoting properties. Six PNSB were selected for their resistance to Mn2+ in acidic conditions (pH 3.5–5.5). They were identified as Rhodopseudomonas palustris strains TLS12, VNS19, VNS32, VNS62, and VNW95, and Rhodopseudomonas harwoodiae strain TLW42. Under aerobic dark and microaerobic light incubating conditions in aqueous solution at pH 4.25 for 30 min, these strains adsorbed Mn2+ (1500 mg L−1) more effectively with released exopolymeric substances (EPS) than with their biomass. Under both incubating conditions, bioaccumulation of Mn2+ diminished in the following order: cell wall, cytoplasm, plasma membrane. Scanning electron microscope-energy dispersive X-ray spectrometry (SEM-EDS) found accumulated manganese (0.30–0.67% of total elements) in bacterial cells caused morphological change in the form of wrinkles and bleb-like features on exterior surfaces. All selected strains under both incubating conditions released NH4+ by N2 fixing and PO43− by solubilizing phosphate from various P-sources. Siderophores, 5-aminolevulinic acid (ALA), and indole-3-acetic acid (IAA) were also released and pH increased. The studied strains showed potential as bioremediators that could reduce Mn2+ toxicity using EPS and effectively release nutrients and plant growth promoting substances to improve cultivation and fertility in acidic conditions.

中文翻译：

---

从酸性硫酸盐土壤中分离的抗 Mn2+ 紫色非硫细菌通过抗性机制作为生物修复剂和植物生长促进剂的潜力

研究了酸性 Mn2+ 抗性紫色非硫细菌 (PNSB) 的抗性机制，以确定它们减轻过量锰对酸性硫酸盐土壤 (ASS) 中植物生长和生产力的不利影响的能力。PNSB 是根据它们对酸和锰的抗性来分离和选择的。根据生物吸附、生物积累和植物生长促进特性评估了它们的抗性机制。选择了 6 种 PNSB，因为它们在酸性条件下（pH 3.5-5.5）对 Mn2+ 具有抗性。它们被鉴定为沼泽红假单胞菌菌株 TLS12、VNS19、VNS32、VNS62 和 VNW95，以及哈伍德红假单胞菌菌株 TLW42。在pH 4.25的水溶液中在好氧暗和微需氧光条件下孵育30分钟，这些菌株用释放的外聚合物质 (EPS) 比用它们的生物质更有效地吸附 Mn2+ (1500 mg L-1)。在这两种培养条件下，Mn2+ 的生物积累按以下顺序减少：细胞壁、细胞质、质膜。扫描电子显微镜 - 能量色散 X 射线光谱法 (SEM-EDS) 发现细菌细胞中累积的锰（占总元素的 0.30-0.67%）会导致外表面皱纹和气泡状特征形式的形态变化。在两种孵育条件下，所有选定的菌株通过固定 N2 释放 NH4+，通过溶解来自各种 P 源的磷酸盐释放 PO43-。铁载体、5-氨基乙酰丙酸 (ALA) 和吲哚-3-乙酸 (IAA) 也被释放并且 pH 值升高。