Bacteria are capable of forming inorganic crystals either intracellularly or extracellularly. Calcite (calcium
carbonate) precipitation is a well-known example of extracellular bacterial biomineralization. Certain species of marine
moderately halophilic bacteria have been shown to precipitate minerals in water supplemented with artificial marine salt
media and differing Mg²+:Ca²+ concentration ratios. Formation of fluorescent calcite associated with specific catalysis by
the thermophilic bacterium Geobacillus thermoglucocidasius and its possibility for industrial application is also
documented. Although various chemical methods have been extensively developed for recovering precious metals from
aqueous solutions, another possible method is recovery using intracellular microbial reduction of gold ions in solution.
Microbial recovery of precious metals is potentially attractive as an environmentally friendly alternative to conventional
methods. Researchers and engineers in materials science have only recently begun to focus on biomineralization. This
review discusses seminal historical and recent research on bacterial biomineralization and its applications, focusing on the
formation of calcite and precious metal-containing crystal species. Additionally, bacterial calcification as it relates to the
panspermia theory is discussed.
Keywords: Biomineralization, calcification, calcite, fluorescent calcite, Geobacillus thermoglucocidasius, panspermia theory.
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