The reduction of sulfate to hydrogen sulfide, which acts as a terminal electron acceptor. Sulfate is activated to adenosine-phosphosulfate (APS) which is then reduced to sulfite, which is in turn reduced to hydrogen sulfide. [ http://www.ncbi.nlm.nih.gov/pubmed/25400653 http://www.ncbi.nlm.nih.gov/pubmed/26680199 ]