Microbial impact on polysulfide dynamics in the environment

Polysulfides (S-x(2-)) are sulfide oxidation intermediates that are important for a variety of environmentally relevant processes including pyrite formation, organic matter sulfidization, isotope exchange among reduced sulfur species, and metal chelation. In addition to their chemical reactivity, laboratory experiments with microbial cultures and enzymes indicate both indirect and direct roles for microorganisms in affecting polysulfide chemistry in natural environments through production and consumption. As polysulfides have been detected in a wide array of natural systems ranging from microbial mats to hydrothermal vents, constraining their biogeochemical cycling has broad impacts. However, many questions remain regarding the processes responsible for polysulfide dynamics in these environments and the precise role that microorganisms play in these processes. This review provides a summary of laboratory experiments investigating the role of polysulfides in microbial metabolism, and observations of polysulfides in the environment in order to provide further insight into and highlight open questions about this significant component of the sulfur cycle.