In the present study halotolerant bacteria were isolated from saline soil (EC ~ 11.9). Based on salt tolerance and plant growth promoting characteristics isolate AF7 was selected for further study. It was identified as Alcaligenes sp. on the basis of protein profiling and 16S rRNA sequence homology. Interestingly, AF7 showed diverse PGP characters at different salinity levels. While phosphate solubilization activity was expressed up to 300 mM NaCl, siderophore production was shown up to 700 mM, zinc solubilization up to 1000 mM and indole acetic acid (IAA), gibberellic acid (GA) and exopolysaccharides (EPS) production were depicted till 1400 mM. Correlative and regression analysis suggested positive relation between IAA, GA, EPS, siderophore production and zinc solubilization capability of AF7 and salinity up to 300 mM NaCl. EPS was found to be the most significant response and there was 263% increment in presence of 300 mM NaCl when compared to non-saline control. Analysis also showed that while growth promoting attributes were significant up to a threshold salinity level, further increasing the stress deviates the mechanism towards survival involving proline, antioxidant and hydroxyl scavenging activities. Combination of halotolerant AF7 and EPS showed more than twofold increase in the vegetative growth parameters of rice at ~ 170 mM NaCl (EC 9 dS/m). The study shows the mechanisms/metabolites of the plant growth promoting bacterium (PGPB) AF7 prominently involved during the salinity stress. Study also proves that novel bioformulations can be developed by integrative use of EPS and salt tolerant-PGPB which can be effective for saline soils.

在本研究中，耐盐细菌是从盐渍土中分离出来的（EC ~ 11.9）。基于耐盐性和促进植物生长的特性，选择分离株AF7进行进一步研究。它被鉴定为Alcaligenes sp。基于蛋白质分析和 16S rRNA 序列同源性。有趣的是，AF7 在不同盐度水平下表现出不同的 PGP 特征。磷酸盐溶解活性最高可达 300 mM NaCl，铁载体产量最高可达 700 mM，锌溶解最高可达 1000 mM，吲哚乙酸 (IAA)、赤霉酸 (GA) 和胞外多糖 (EPS) 产量最高可达 1400 mM毫米。相关和回归分析表明，IAA、GA、EPS、铁载体产量和 AF7 的锌增溶能力以及高达 300 mM NaCl 的盐度之间存在正相关关系。发现 EPS 是最显着的反应，与非盐水对照相比，在 300 mM NaCl 存在下，EPS 增加了 263%。分析还表明，虽然在达到阈值盐度水平时，生长促进特性很显着，但进一步增加压力会偏离涉及脯氨酸、抗氧化剂和羟基清除活性的生存机制。耐盐 AF7 和 EPS 的组合显示，在约 170 mM NaCl (EC 9 dS/m) 下，水稻的营养生长参数增加了一倍以上。该研究表明植物生长促进细菌 (PGPB) AF7 的机制/代谢物在盐度胁迫过程中发挥着重要作用。研究还证明，通过综合使用EPS和耐盐-PGPB可以开发出对盐渍土壤有效的新型生物制剂。