Alleviation of metal stress by Pseudomonas orientalis and Chaetomium cupreum strains and their effects on Eucalyptus globulus growth promotion

Abstract

Pseudomonas orientalis and Chaetomium cupreum isolated from metal(oid)s-contaminated soil were characterized to evaluate their role in plant growth promotion and enhance the tolerance of Eucalyptus globulus to copper stress. We evaluated minimum inhibitory concentration and explored plant-promoting traits under copper stress. Moreover, changes in morphology and the accumulation of metals on the cell surface were determined by scanning electron microscopy images coupled with energy dispersive x-ray spectroscopy (SEM-EDX). The effect of inoculation with P. orientalis and C. cupreum on E. globulus plants established in soils contaminated with copper was determined through root and shoot biomass and antioxidant response. Both strains showed high tolerance to metal(oid)s, whereas phosphate solubilization was only detected in P. orientalis. Under copper stress, C. cupreum presented a higher production rate of siderophores and indole acetic acid (4.5 mm day−1, 15.042 μg mL−1). SEM images and EDX analysis reflected cellular changes in fungus and proved biosorption of copper. Inoculation of P. orientalis and C. cupreum on Eucalyptus globulus plants significantly increased plant growth and mitigated the toxic effects of copper. According to these results, both microorganisms contribute positively to stimulated plant growth and to decreasing stress caused by high concentrations of copper in soil, especially C. cupreum.