Innovative biotechnological process for microcystins decontamination of plant-soil complex using rhizospheric microorganisms

In many countries located in arid and semi-arid areas, irrigation with raw water from lake-reservoirs is a common agricultural and horticultural practice, and an important tool for farmers to improve crop yields. This kind of surface water bodies can contain potentially toxic bloom-forming cyanobacteria, and its use as a source for irrigation water can enable a transfer of cyanobacterial toxins (cyanotoxins) into crop plant. When these toxins are accumulated in crop plants it poses serious human health risk when they enter the food chain. One important group of cyanotoxins is microcystin (MC). MCs are not well removed by conventional water treatment practices and require more costly treatments such as activated carbon and/or advanced oxidation processes, which themselves may have limitations. Bioremediation is an alternative to physicochemical treatments, since some genera of bacteria are known to degrade MCs. The key step in MCs degradation is the cleavage of the peptide ring in order to give a linear peptide. This reaction is catalyzed by the enzyme MlrA which is an endopeptidase able to hydrolyze the ADDA-R bond. Once the peptide is linearized, additional peptidases (MlrB, MlrC and MlrD) can hydrolyze it leading to non-toxic end products. The operon mlrABCD from a number of MCs-degrading bacteria have been sequenced and the sequences deposited in public database. The comparison of the sequences will allow us to find consensus sequences, which will be used to amplify MCs degrading genes in the bacterial populations of plants irrigated with MCs containing waters. To our knowledge, up to now only two soil microorganisms were shown to be able to degrade MCs, which is not enough to be used as biocontrol agent against MCs in plant soil-system. Furthermore, these two microorganisms belong to the same genera and their effectiveness in plant soil-system was not tested. The main objective of this project is to construct a bank of soil microorganisms able to degrade MCs to protect plants from MCs introduced via irrigation water, and to study the integration of these microorganisms in the field as biocontrol agent against MCs. We project to improve crop production, agriculture and food security. The generation of a biotechnological tool for degradation of MCs in soils may be reducing the risk of MCs to plants and humans.