Thermophilic Chemolithotrophic Bacteria in Mining Sites

Abstract

Microorganisms which inhabit extremely acidic environments are increasingly attracting the attention of researchers because of their peculiar physiology. These extremophiles play a huge role in geochemical processes in mining sites and environmental pollution by heavy metals. They also have important applications in biotechnology of metals. The study of biodiversity and relevant biogeochemical processes is of great interest for improving metal leaching technologies and developing countermeasures for the formation of acid mine drainage (AMD). Due to the insufficient data of ecology of chemolithotrophic bacteria inhabit natural and technogenic biotopes of sulfide ores in Armenia, studies of biodiversity and dissemination of these bacteria in the copper, copper-molybdenum, gold-bearing, and polymetallic ore deposits of Armenia were performed. Using enrichment media and isolation techniques, new and original strains of sulfur- and/or iron-oxidizing bacteria (SIOB) were isolated and studied. Based on physiological and biochemical peculiarities as well as molecular biological studies, the isolated strains were identify as Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, L. ferriphilum, and Sulfobacillus thermosulfidooxidans subsp. asporogenes. In this paper we have made an attempt to summarize the data obtained concerning dissemination of moderate thermophilic and thermotolerant SIOB and their biological properties as well as abilities to oxidize the most abundant minerals, pyrite and chalcopyrite. Their role in geochemical processes occurring in mining sites as well as bioleaching of the most abundant minerals pyrite, chalcopyrite, and refractory gold-bearing ores were evaluated.