Plant chemicals to promote rhizoremediation of POP-contaminated brownfields

点击翻译按钮获取中文摘要

Rhizosphere is the zone surrounding plant roots where complex interactions take place between plants, and microorganisms. The bacteria living in association with plant roots are called plant growth promoting rhizobacteria (PGPR). This association is highly beneficial for both organisms. PGPR protect plants against diseases and they produce plant growth stimulators. In return, plants exude compounds that are beneficial for overall activities of PGPR. Exudates contain chemicals that act as signal to promote the root colonization process by PGPR and others such as flavonoids and terpenes that may induce catabolic pathways involved in the degradation of soil organics including persistent pollutants (POPs) such as polychlorinated biphenyls (PCBs). Therefore, rhizoremediation is a process in which plants pump contaminants to the rhizosphere and release chemicals that promote rhizobacterial growth and induce their POP catabolic pathways. Rhizoremediaton is among the most suitable technology for remediating brownsfields since its cost is 50 to 80% lower than alternatives and it requires a minimum of intervention. The objectives of this proposal are 1- to identify plant root exudates components that induce root colonization traits of rhizobacteria, thus facilitating their implantation and survival in soil; 2- to identify exudates components that induce PCB degradation by PCB-degrading rhizobacteria. These chemicals will be of high commercial value as they should provide an additional tool to assist the phytoremediation processes. The specific objectives will be 1- to screen for natural PGPR from crucifers or legumes exhibiting the dual ability of utilizing phenylpropanoids and degrading POPs; 2- To identify chemicals from plant exudates [crucifers (Arabidopsis thaliana) and legumes (Medicago sativa, alfalfa plant)] that act as effector to induce plant root colonization traits by PGPRs; 3- to evaluate the effect of chemicals from plant root exudates on expression of rhizobacterial PCB degrading genes; 4- To assess the influence of the effectors identified in objective 2 and 3 in microcosm assays.