Browsing by Author "Zhang, Chang"
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- Bioaugmentation with Endophytic Bacterium E6S Homologous to Achromobacter piechaudii Enhances Metal Rhizoaccumulation in Host Sedum plumbizincicolaPublication . Ma, Ying; Zhang, Chang; Oliveira, Rui S.; Freitas, Helena; Luo, YongmingApplication of hyperaccumulator-endophyte symbiotic systems is a potential approach to improve phytoremediation efficiency, since some beneficial endophytic bacteria are able to detoxify heavy metals, alter metal solubility in soil, and facilitate plant growth. The objective of this study was to isolate multi-metal resistant and plant beneficial endophytic bacteria and to evaluate their role in enhancing plant growth and metal accumulation/translocation. The metal resistant endophytic bacterial strain E6S was isolated from stems of the Zn/Cd hyperaccumulator plant Sedum plumbizincicola growing in metalliferous mine soils using Dworkin and Foster salts minimal agar medium with 1-aminocyclopropane-1-carboxylate (ACC) as the sole nitrogen source, and identified as homologous to Achromobacter piechaudii based on morphological and biochemical characteristics, partial 16S rDNA sequence and phylogenetic analysis. Strain E6S showed high level of resistance to various metals (Cd, Zn, and Pb). Besides utilizing ACC, strain E6S exhibited plant beneficial traits, such as solubilization of phosphate and production of indole-3-acetic acid. Inoculation with E6S significantly increased the bioavailability of Cd, Zn, and Pb in soil. In addition, bacterial cells bound considerable amounts of metal ions in the following order: Zn > Cd >Pb. Inoculation of E6S significantly stimulated plant biomass, uptake and bioaccumulation of Cd, Zn, and Pb. However, E6S greatly reduced the root to shoot translocation of Cd and Zn, indicating that bacterial inoculation assisted the host plant to uptake and store heavy metals in its root system. Inoculation with the endophytic bacterium E6S homologous to A. piechaudii can improve phytostabilization of metalliferous soils due to its effective ability to enhance in situ metal rhizoaccumulation in plants.
- Biochemical and Molecular Mechanisms of Plant-Microbe-Metal Interactions: Relevance for PhytoremediationPublication . Ma, Ying; Oliveira, Rui S.; Freitas, Helena; Zhang, ChangPlants and microbes coexist or compete for survival and their cohesive interactions play a vital role in adapting to metalliferous environments, and can thus be explored to improve microbe-assisted phytoremediation. Plant root exudates are useful nutrient and energy sources for soil microorganisms, with whom they establish intricate communication systems. Some beneficial bacteria and fungi, acting as plant growth promoting microorganisms (PGPMs), may alleviate metal phytotoxicity and stimulate plant growth indirectly via the induction of defense mechanisms against phytopathogens, and/or directly through the solubilization of mineral nutrients (nitrogen, phosphate, potassium, iron, etc.), production of plant growth promoting substances (e.g., phytohormones), and secretion of specific enzymes (e.g., 1-aminocyclopropane-1-carboxylate deaminase). PGPM can also change metal bioavailability in soil through various mechanisms such as acidification, precipitation, chelation, complexation, and redox reactions. This review presents the recent advances and applications made hitherto in understanding the biochemical and molecular mechanisms of plant-microbe interactions and their role in the major processes involved in phytoremediation, such as heavy metal detoxification, mobilization, immobilization, transformation, transport, and distribution.
- Potential of plant beneficial bacteria and arbuscular mycorrhizal fungi in phytoremediation of metal-contaminated saline soilsPublication . Ma, Ying; Rajkumar, Mani; Oliveira, Rui S.; Zhang, Chang; Freitas, HelenaPhytoremediation has been considered as a promising technique to decontaminate polluted soils. However, climatic stress particularly salinity, is a potential threat to soil properties and plant growth, thus restricting the employment of this technology. The aim of this study was to access the impact of microbial inoculation on phytoremediation of nickel (Ni) contaminated saline soils using Helianthus annuus. Salt resistant plant beneficial bacterium (PBB) Pseudomonas libanensis TR1 and arbuscular mycorrhizal fungus (AMF) Claroideoglomus claroideum BEG210 were used. Inoculation of P. libanensis alone or in combination with C. claroideum significantly enhanced plant growth, changed physiological status (e.g. electrolyte leakage, chlorophyll, proline and malondialdehyde contents) as well as Ni and sodium (Na+) accumulation potential (e.g. uptake and translocation factor of Ni and Na+) of H. annuus under Ni and salinity stress either alone or in combination. These results revealed that bioaugmentation of microbial strains may serve as a preferred strategy for improving phytoremediation of metal-polluted saline soils.