Microorganisms play key roles in the biosphere, particularly in the areas of element biotransformations and biogeochemical cycling, mineral transformations, decomposition, bioweathering, and soil and sediment formation. Direct and indirect physical, chemical and biochemical mechanisms are involved in mineral biotransformation by microbes. The role of anaerobic microorganisms and influence of their activity products on geological environmental condition in the weathering zone of lithosphere is discussed. The most important anaerobic microorganisms are sulphate-reducing bacteria (SRB) and methanogenic Archaea. These groups of microorganisms play significant role in biodegradation of organic matter and participate in formation of different kind of mineral phases e.g. carbonates and metal sulphides.
Biotransformation of phosphogypsum in two anaerobic cultures of mesophilic and thermophilic bacteria was investigated. In the both cultures an increase of sulphide ions was found, adequate to reduction of ca 50 % of sulphates in phosphogypsum. The mineral fraction of the post-reaction precipitates was equal to 43 and 35 % of the initial mass of phosphogypsum in the meso- and thermophilic cultures, respectively. It comprised, in addition to the residue of phosphogypsum, calcite (in the mesophilic cultures) or calcite and apatite (in the thermophilic cultures). In the both post-reaction precipitates, concentrations of lanthanides increased from 0.56 % in phosphogypsum substrate to 1.28 % in the mesophilic bacteria cultures, and to 1.47 % in the thermophilic ones.
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