The role of microorganisms in bioremediation and phytoremediation of polluted and stressed soils

Since more than a century, soils, waters, sediments and the subsurface are facing a massive pollution by a large series of chemicals and by chemo-physical stresses. Microorganisms are the major players in counteracting such stresses and recycling elements by mineralizing or partitioning pollutants, even in environments poor in nutrients or lacking availability of major electron donors and acceptors. In chemicalpolluted soils or where salinity and other physical stresses exist, a complex biota that includes microorganisms and plants has to face major challenges for survival and growth. The present review intends to show that an important role for the detoxification processes in the soil environment is played by microorganisms and/or by the interactions between microorganisms and plants where the microbial symbionts promote the plant growth and, in synergy with the host, facilitate plant survival. Here we present some examples of cooperation between different microbial species and between microorganisms and plants highlighting the importance of these interactions. As a first example, the effectiveness of microbial reductive dehalogenation of 1,2-dichloroethane (1,2-DCA) is shown as an emerging important process for remediating groundwater and sediments from recalcitrant halogenated aliphatic and aromatic molecules. As far as with plant microbe interactions, it is shown from the literature that microorganisms can remarkably facilitate plant survival and growth under stressing conditions like those affecting arid and saline soils. It is proposed that in the future the plant ecosystem should be considered in its whole biota complexity in which, besides plants, the plant-associated microorganisms play a key role for crop sustainability and soil remediation. Finally, it is discussed that the understanding of the interactions and the ecological relationships between microorganisms and between microorganisms and plants from both mechanistic and theoretical perspectives is mandatory for addressing the global environmental problems our planet are facing. bioremediationmicrobial ecologymicrobial functionalityphy-toremediation.