This lecture covers the process of sulfate reduction, focusing on the biochemical pathways involved, such as dissimilatory vs. assimilatory S0²- reduction, the challenge of obtaining a proton gradient, and the role of sulfate-reducing bacteria. It also discusses the geochemical implications of sulfate reduction, including the production of sulfide and its reaction with iron. Additionally, the lecture explores the disproportionation of sulfur-bearing compounds and the impact of sulfate reduction on corrosion in steel-bearing structures.