ACCUMULATION AND REDUCTION OF ARSENIC BY Tetrahymena thermophila strain SB-4220

Arsenic biotransformation is thought to exist widely in various environments, which have been observed in previous studies. Tetrahymena thermophila is a species of free-living ciliated protozoan that mostly distribute in the freshwater environments around the world. In this study, we studied the transformation, accumulation and efflux of arsenic species within the T thermophila (strain SB-4220) cells. The results indicate that SB-4220 preferred to reduce and accumulate arsenic intracellularly since arsenite was the main compounds found within the cells in both As(III) and As(V) treatments, and extruded arsenite from the cells were barely detected in the medium. A series of toxicological experiments were also carried out and results from growth curves, flow cytometric analysis suggest that arsenic did not have significant effects on the growth, mortality and morphological characters of SB-4220. It was also concluded that SB-4220 might have a relatively high tolerance to arsenic stress.