Metabolic Capacity of the Antarctic Cyanobacterium That Sustains Oxygenic Photosynthesis in the Presence of Hydrogen Sulfide.

Sulfide inhibits oxygenic photosynthesis by blocking electron transfer between HO and the oxygen-evolving complex in the D1 protein of Photosystem II. The ability of cyanobacteria to counter this effect has implications for understanding the productivity of benthic microbial mats in sulfidic environments throughout Earth history. In Lake Fryxell, Antarctica, the benthic, filamentous cyanobacterium creates a 1-2 mm thick layer of 50 µmol L O in otherwise sulfidic water, demonstrating that it sustains oxygenic photosynthesis in the presence of sulfide.