Sulphate metabolism among thermophiles and hyperthermophiles in natural aquatic systems

Although controversial, the idea that hydrothermal systems may have been the site for prebiotic synthesis of organic molecules and origin of life is widely supported. For the nascent life to survive, it must have had some sort of metabolic mechanism for generating energy. However, little is known of the specific metabolic pathways utilized by the early life forms or the effect of high temperatures on their activity. Recent research on natural high temperature aquatic environments, though limited because of difficult field logistics and experimental problems, is revolutionizing our understanding of possible energy-generating redox pathways, such as sulphate reduction. An abridged review of research on thermophilic sulphate reduction is presented here. Because of a complex interplay between microbiological and geochemical entities involved, and the uncertainties that modern hydrothermal systems are proxy for biogeochemical conditions on early Earth, great caution is required for interpretation and extrapolation of data from these studies to primordial times. Furthermore, a general lack of integrated geological and microbiological studies towards a common understanding of origin and sustenance of life on Earth is starkly evident from this review.