Metal uptake and biotransformation in lichens: Case study of arsenic

Tanja MRAK (Ljubljana): Lichens acquire the substances from the environment in two ways: by entrapment of particles and by uptake of ions from the solution. In the case of excessive amounts of metals and metalloids, toxic effects can be avoided by extracellular and intracellular detoxification mechanisms. Most of the studies of metal uptake, biotransformation and detoxification in lichens were done on cationic forms of metals. Our study was performed on arsenic, a metalloid that occurs in the environment mainly in the anionic form and forms numerous inorganic and organic compounds. Lichens were exposed to As(V) which is the most common arsenic compound in the environment. Uptake patterns in dependence of time and arsenic concentration were followed and arsenic compounds in the exposure solution and in the lichen thalli determined. From the results which will be presented in the lecture it is evident that for at least two detoxification mechanisms for arsenic exist in lichens. In addition, the lecture will provide a brief overview of the influence of arsenic on selected biochemical parameters of lichens (glutathione, cystein, phytochelatins, photosynthetic pigments).