Isolation and engineering of plant growth promoting rhizobacteria Pseudomonas aeruginosa for enhanced cadmium bioremediation

[摘要] Although many bacteria are tolerant to heavy metals and play important roles in the immobilization of heavy metals, they cannot always be dependably reproduced under field conditions. In this work, a cadmium (Cd)-resistant bacterium was isolated from a Cd-contaminated oil field and identified as Pseudomonas aeruginosa (Pse-w). We then determined various plant growth promoting features such as the solubilization of phosphate, and the production of indole-3-acetic acid and siderophores. Lastly, we engineered the strain Pse-w-MT by targeting metallothioneins to the cell surface of Pse-w to immobilize Cd2+ and promote plant growth. Our data revealed that Pse-w exhibited high levels of resistance to Cd2+ (4 mM) and showed various plant growth promoting features. The engineered strain Pse-w-MT was found to adsorb Cd2+ mainly via extracellular deposition, and had an enhanced ability for immobilizing Cd2+ ions from the external media. Furthermore, the inoculation of Cd-polluted soil with Pse-w-MT significantly elevated the shoot and root biomass and leaf chlorophyll content. Similarly, plants inoculated with Pse-w-MT demonstrated markedly lower Cd2+ accumulation in the root and shoot system. It was concluded that plant growth promoting rhizobacteria with a high Cd2+ tolerance was an ideal candidate to be engineered for bioremediation and plant growth promotion against Cd-induced stress.

[学科分类] 微生物学和免疫学

[关键词] cadmium tolerance;metallothionein;plant growth promoting rhizobacteria;Pseudomonas aeruginosa;surface-display