The effect of soil bioaugmentation with strains of Pseudomonas on Cd, Zn and Cu uptake by Sinapis alba L.

Highlight
• Selected strains of P. putida and P. fluorescens alter metal uptake by Sinapis alba.
• Strains MH3, MH7, MH9 and MH15 increased the plant biomass.
• The bacterial strains had various mechanism of plant growth promotion.
• P. fluorescens MH15 seems to be the best candidate for enhancement of phytoextraction.

The aim of this study was to assess the ability of selected metal resistant strains of the Pseudomonas genus to increase Zn, Cd and Cu uptake by the metalophyte Sinapis alba L. under laboratory conditions. Moreover, the mechanisms of the plant growth promotion in the tested strains and their impact on the shoots and roots of white mustard biomass were examined. Soil inoculation with the tested strains resulted in higher concentrations of Zn, Cd and Cu in the shoots and roots of the plants in comparison with those grown in non-inoculated soil. The highest phytoextraction enhancement was caused by Pseudomonas fluorescens MH15 which increased Zn, Cd and Cu accumulation in shoot tissue by 60%, 96% and 31%, respectively, in comparison with control plants. Moreover, all the tested strains also exhibited a significant increase of Cd translocation from roots to shoots of the white mustard. Three Pseudomonas putida (MH3, MH6, MH7) and two P. fluorescens biotype G and C (MH9 and MH15, respectively) strains had the ability to produce siderophore, 1-amino-cyclopropane-1-carboxylic acid deaminase, indole 3-acetic acid as well as hydrocyanic acid. Additionally, P. putida strains were also capable of solubilizing inorganic phosphate. The ability of the tested strains to increase the metal uptake in white mustard and their plant growth-promoting properties make them good candidates for supporting heavy metal phytoextraction as well as for plant growth promoting.