Abstract

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.