Microbiology Laboratory, Department of Botany, The University of Burdwan, Burdwan, WB, PIN 713104, India.
Department of Botany, Government General Degree College, Singur, WB, PIN 712409, India.
Environ Sci Pollut Res Int. 2017 Nov;24(31):24419-24437. doi: 10.1007/s11356-017-0033-z. Epub 2017 Sep 11.
Cadmium (Cd) phytotoxicity in agricultural land is a major global concern now-a-days resulting in very poor yield. Plant growth-promoting rhizobacteria (PGPR)-mediated bioremediation is one of the convenient strategies for detoxification of Cd from the soil and for plant growth promotion under Cd stress. The selected strain K5 was identified as Klebsiella pneumoniae based on MALDI-TOF MS ribosomal protein and 16S rDNA sequence-based homology. The strain possessed several PGP traits viz. IAA production (3413 μg/mL), phosphate solubilization (80.25 ppm), ACC deaminase activity (40 ng α-ketobutyrate/mg protein/h), N fixation ability (1.84 μg N fixed/h), etc. and has the highest Cd resistance (4000 μg/mL) among Cd-resistant PGPR so far reported. This strain efficiently accumulated Cd and remained viable under Cd stress as confirmed by AAS-TEM-EDX analysis and viability test, respectively. The significant (p < 0.05) positive effect of the strain was reflected in various plant growth parameters like increased seed germination (50 to 90%), root length (5-fold), shoot length (about 2-fold), root fresh weight (> 2-fold), and shoot fresh weight (1.23-fold) under Cd stress compared with uninoculated set. Moreover, the positive impact of this strain on antioxidant enzyme activity (CAT, MDA, SOD) and several other biochemical parameters (proline, α-amylase, protease, total sugar, total protein, chlorophyll content) were also measured that favors plant growth promotion under Cd stress. Besides, the K5 strain also decreased stress-ethylene level under Cd stress and reduction of Cd accumulation in seedling (> 1.5-fold) was conducive to alleviate Cd phytotoxicity. Hence, K. pneumoniae strain K5 can be used as a phytostimulating and Cd-bioremediating biofertilizer for sustainable agriculture in heavy metal-contaminated sites.
镉（Cd）在农业用地中的植物毒性是当前全球主要关注的问题，导致产量非常低。植物促生根际细菌（PGPR）介导的生物修复是从土壤中解毒 Cd 和在 Cd 胁迫下促进植物生长的一种便捷策略。根据 MALDI-TOF MS 核糖体蛋白和 16S rDNA 序列同源性，选择的菌株 K5 被鉴定为肺炎克雷伯氏菌。该菌株具有几种 PGPR 特性，如 IAA 生产（3413μg/mL）、磷酸盐溶解（80.25ppm）、ACC 脱氨酶活性（40ngα-酮丁酸/mg 蛋白/h）、固氮能力（1.84μgN 固定/h）等，并且具有迄今为止报道的 Cd 抗性最高的菌株（4000μg/mL）。该菌株通过 AAS-TEM-EDX 分析和活力测试分别在 Cd 胁迫下有效地积累 Cd 并保持存活。该菌株对各种植物生长参数的显著（p<0.05）积极影响，表现在种子发芽率（增加 50-90%）、根长（增加 5 倍）、茎长（增加约 2 倍）、根鲜重（增加 2 倍以上）和茎鲜重（增加 1.23 倍）等方面，与未接种的对照组相比。此外，还测量了该菌株对抗氧化酶活性（CAT、MDA、SOD）和其他几种生化参数（脯氨酸、α-淀粉酶、蛋白酶、总糖、总蛋白、叶绿素含量）的积极影响，有利于在 Cd 胁迫下促进植物生长。此外，K5 菌株还降低了 Cd 胁迫下的应激乙烯水平，并减少了幼苗中 Cd 的积累（增加 1.5 倍以上），有利于减轻 Cd 的植物毒性。因此，肺炎克雷伯氏菌 K5 菌株可作为重金属污染场地可持续农业的植物刺激和 Cd 生物修复生物肥料。
