The Complex Interplay of Sulfur and Arsenic Bioenergetic Metabolisms in the Arsenic Geochemical Cycle

Geochemical cycles of arsenic and sulfur are largely impacted by the activity of prokaryotes as microorganisms use these two elements for assimilatory and dissimilatory purposes. Knowledge of the enzymatic systems responsible for these processes is thus essential for understanding the geochemical cycles of both elements. But arsenic and sulfur commonly co-exist in the environment, leading to the formation of thiolated arsenic species with one to four arsenic-bonded oxygen atoms substituted by sulfur. Considering these chemical species and the biological processes at the heart of their formation and transformations is therefore crucial for comprehending the complexity of the global geochemical cycles of arsenic and sulfur. This chapter offers a comprehensive overview of the well-known prokaryotic arsenic and sulfur enzyme systems responsible for use of these two elements in bioenergetics, as well as the ever growing-group number of prokaryotic enzymes revealed to be able to convert thioarsenic species or to convert both arsenic and sulfur.