Recognition of the biological nature of sulphate reduction in natural environments, and identification of the bacterial species involved dates to the latter part of the nineteenth century, and the seminal work of such giants of the early days of microbiology as Beijerinck andWinogradsky. The central role of environmental studies in highlighting the issues to be addressed and the problems to be solved, has remained to this day a constant theme in microbiological analyses of the sulphate reducers. The modern era of such analyses, however, can be said to date from the period around 1960 when the demonstrations by Postgate and Peck, respectively, of the presence of cytochromes and of phosphorylation linked to anaerobic respiration in sulphate-reducing bacteria (SRB), fundamentally altered our view of the biochemical nature of these organisms and, in particular, of their mechanisms of energy conservation.