Light not needed for this. Need lots of energy to drive this reaction, so need an extra step. Light is needed for this. Chromatium vinosum , Thiospirillum jenense Purple nonsulfur bacteria . Proton gradient is produced, ATP is made as protons flow back through ATP synthase molecules.
Specific carriers are different.
Sulfur accumulates inside cells when H 2 S is used, hence the name. Sulfur accumulates outside cells. See handout on Oxygenic Photosynthesis. The longer, clearer cells are heterocysts, specialized cells that fix nitrogen. View light micrograph of Oscillatoria x1000, another filamentous cyanobacterium.