Arsenic response in Coccomyxa sp. deciphered by non-targeted metabolomic and transcriptomic analysis. Coccomyxa sp. Carn transcriptome

Arsenic is a toxic metalloid known to generate an important oxidative stress in cells. In the present study we focused our attention on an alga related to the genus Coccomyxa, which was isolated from an acid mine drainage (AMD) presenting very high concentrations of the water soluble form, arsenite. Physiological observations combined with differential transcriptomic and non-targeted metabolomic analyses highlighted multiple levels of protection against this toxic compound. Indeed, Coccomyxa sp. induced a set of transporters potentially preventing the accumulation of this metalloid in the cells and presented a distinct arsenic metabolism in comparison to an other specie more sensitive to that compound, i.e. E. gracilis, especially in regard to arsenic methylation. Surprisingly, Coccomyxa sp. did not seem to be exposed to an important oxidative stress in the presence of arsenite, which is likely linked to intracellular accumulation of high levels of strong antioxidants such as ascorbic acid and glutathione. Our results therefore suggest that this alga has acquired multiple and original defense mechanisms allowing the colonization of extreme ecosystems such as AMDs.