Sulfate respiration is one of the major modes of anaerobic respiration in anoxic environments. This ancient microbial metabolism plays a critical role in the biogeochemical sulfur cycle, and is also important in the gut. Sulfate respiration displays some unique metabolic features, and how microorganisms obtain energy from this process has not been fully established. We investigate the respiratory metabolism of sulfate reducers, which will give us important clues into the evolution of Life on the early earth, and is crucial for exploiting these organisms in biotech applications or for controlling the damaging side-effects of their activity (for example in biocorrosion or in microbiota-associated diseases like colorectal cancer and inflammatory bowel diseases). We focus on the metabolic pathways involved in sulfate/sulfite respiration, and have characterized several essential membrane complexes for the first time, which was an important breakthrough into understanding the mechanism of this process. We also discovered the presence of an additional step in dissimilatory sulfate reduction, involving a protein trisulfide as the product of sulfite reduction. Ongoing studies focus on how the membrane complexes interact with other proteins in metabolic pathways to achieve energy conservation.