High resolution profiling of sulfur and oxygen speciation in microbial mats: Implications for coupling of hydrogen peroxide with sulfur species

Hydrogen sulfide is produced in microbial mats by sulfate reducing bacteria, and diffuses towards the surface until it is consumed. Cyanobacteria in these mats are able to produce oxygen photochem., and when subjected to high UV light intensity, can also produce hydrogen peroxide. Microelectrodes have proven to have sufficient resoln. to resolve the sulfur and oxygen chem. in these mats, demonstrating the links between these populations of bacteria in modern mats. In sulfur-dominated cyanobacterial mats in several settings, we have obsd. both high hydrogen sulfide fluxes and the periodic prodn. of significant amts. of hydrogen peroxide at times of high UV stress using voltammetric Au-amalgam microelectrodes. We review the use of voltammetric and amperometric microelectrodes in approaching this chem., and how the relative rates of sulfur species oxidn. with oxygen or peroxide may play a significant role in shaping the chem., isotopic, and biol. compn. of these systems.