Bacterial involvement in apatite genesis

Bacteria initiated apatite genesis from organic matter in laboratory-controlled conditions. However, the synthesis of apatite, which takes place from inorganic phosphate and aragonite (CaCO3), appears to be independent of the presence of microorganisms. In vitro experiments using bacterial alkaline phosphatase or calf intestine phosphatase in a definite sterile medium in which the phosphorus source is represented by nucleotides from total yeast RNA, and in vivo experiments with Escherichia coli constitutive alkaline phosphatase mutants, showed the involvement of the alkaline phosphatase with releasing inorganic phosphate in the medium. A strain identified as Providencia rettgeri which in the presence of RNA converts the aragonite to apatite in a few days was isolated from a non-sterile assay. Such a mechanism is proposed to explain the natural formation of apatite in sediments.