Chemical pollution of natural waters has become a major public concern. Millions of tons of synthetic organic chemicals (OCs) are used annually for industrial, agricultural and consumer’s purposes. These compounds partially find their way to the aquatic environment affecting water quality with consequences for aquatic life. Adverse outcomes of OCs on the biota are directly linked to the ability of the organism to face the toxic insult. Organisms dispose of different defense strategies to deal with OCs and to detoxify those accumulated within their body. Among the multiple detoxification strategies, biotransformation plays a prominent role. Investigation of biotransformation activities has now reached recognized importance in ecotoxicology, providing mechanistic information on the toxic action that OCs may have on the biota. Furthermore, biotransformation studies indicate to what extent organisms may contribute to the fate of OCs in the ecosystems. Transformation products (TPs) generated by organism’s metabolism can be released in the natural environment or enter the food chain, multiplying the number of molecules with anthropic origin in natural ecosystems. Today, the scientific community and policy makers agree on the necessity to include TPs in chemical pollution monitoring and risk assessment for proper environmental protection. Finally, deeper knowledge on biotransformation pathways is required for optimization of pollution removal during waste water treatment processes.
In line with the scientific and societal needs, the general aim of the PHYCOCYP project was to get a mechanistic understanding of the biotransformation processes and their role in phytoplankton tolerance to organic contaminants.
The project focused its research on a group of enzymes, the Cytochrome P450 (CYP), that play a prominent role in biotransformation in higher organisms but that were underexplored in phytoplankton. Phytoplankton are aquatic photosynthetic microorganisms that play a key role in the water food chain and global nutrient cycling, contributing to about half of global primary productivity and being a major sink of carbon dioxide in oceans. Chemical pollution due to anthropogenic activities may considerably affect phytoplankton with consequences on biogeochemical cycling and food chain dynamics. Investigations of OCs biotransformation in phytoplankton is of fundamental importance to improve our understanding of phytoplankton stress responses to contaminant pollution and better assess OCs impact on aquatic environments.
The objectives of the proposed research were i) to investigate the possible role of CYPs as biomarker of OC exposure in phytoplankton, ii) to gain a mechanistic insight in CYP mediated stress responses and biotransformation processes.
To reach this goal the work was organized in three work packages (WPs) that included research and training activities. An integrated multidisciplinary approach was adopted thanks to multiple collaborations with ecotoxicologists, analytical chemists, ecophysiologists and phytoplankton biologists.
The research activities conducted in the PHYCOCYP project indicated that CYPs in phytoplankton are involved in contaminants biotransformation processes. The concentration and composition of diclofenac transformation products were altered in cells treated with CYP inhibitors indicating that CYPs are involved in diclofenac biotransformation pathways. However, CYP genes expression was not directly regulated by OC exposure. CYP activity, besides being important for detoxification via biotransformation processes, resulted to have a role in other stress response pathways (e.g. oxidative stress responses). As a consequence, CYP genes expression cannot be used as a robust biomarker of contaminants exposure in phytoplankton.
