About this Research Topic
Soil contaminated by inorganic and organic pollutants has become a serious problem in the world. Phytoremediation is a cost-effective environmental benign alternative to traditional soil remediation technologies, but has experienced varied success in practice. The goal of phytoremediation is to utilize plants to immobilize, extract inorganic or degrade organic contaminants. In most cases, plants essentially act indirectly through the stimulation of rhizosphere microbes. The effect of the activities of beneficial rhizosphere microbes could help optimize phytoremediation by indirectly enhancing plant growth or directly facilitating the degradation of organic pollutants and altering soil metal bioavailability (bioaugmentation). Plant growth promoting bacteria (PGPB) and arbuscular mycorrhizal fungi (AMF) both possessing plant growth promoting traits (such as nitrogen fixation, production of indole-3-acetic acid, 1-aminocyclopropane-1-carboxylate deaminase, siderophore, surfactants, solubilization of phosphate) can enhance the growth and health of the remediating plants as biofertilizers. Moreover, the presence of AMF in the established phytoremediation systems may contribute to the underground short term storage of carbon, not only by retaining carbon transferred by the host plant as photosynthate, but also through the stabilization of soil aggregates. In case of organic pollutants, the addition of microbes with specific metabolic capabilities (e.g. pollutant degrading bacteria and fungi) that are under-represented in the natural microbial populations can promote phytoremediation, since they can use some other carbon and energy source to partially degrade contaminant or metabolize contaminant degradation products to carbon dioxide and water, through phytostimulation. For heavy metal decontamination, acidification of metal mobilizing bacteria and release of organic acids from remediating plants are two key mechanisms employed in phytoextraction, whereas precipitation of metal immobilizing bacteria and release of root exudate (amino acids, sugars, enzymes) are useful in phytostabilization. However, the knowledge on understanding of soil microbial communities and plant metabolism, and some of the conditions that promote predictable activity in contaminated soils is far from complete. The aim of this Research Topic is to present and compare recent results on our understanding of integrated activity patterns between plants and microbes, and determine how the reliable environmental technology can be modified to maximize growth, appropriate assembly of microbial communities, and ultimately phytoremediation activity.