Microbiological Reduction of Sulphates in Salty Environments and Mineralogical Characterization of the Transformation Products

This research was focused on the selection, growth and identification of SRB from soils that were subjected to long-term activity of brine, and an evaluation of mineral phases formed during the biodegradation of organic compounds and sulphate reduction. Isolated communities of anaerobic microorganisms were incubated on Postgate C medium with lactate and/or ethanol as the sole carbon source and were adapted for growth at 4% NaCl. Active reduction of sulphates with simultaneous biodegradation of organic compounds was observed in all cultures. The largest reduction of sulphates was noted in cultures with lactate as the sole carbon source; it reached 1438 mg/L, which corresponds to a 43% reduction of sulphates introduced to the medium. SRB activity in the biodegradation of organic compounds varied between 20 and 80% and depended on the level of salinity of the environment in which the SRB communities were isolated, and on the electron donor applied. The presence of biotransformation products in the post-culture deposits in the form of elemental sulphur reflects the activity of the communities. Additionally, the influence of selected communities on the salinity index was analyzed. Active SRB communities decreased the salinity of the environment by as much as 50%. Sulphate-reducing bacteria are an important group of anaerobic microorganisms, especially considering their participation in such geological processes as mineral precipitation and mineralization of organic matter in extreme environmental conditions, including high salinity.