Carbonate-mineralization microbe (Bacillus) was chosen to study the influences of concentration of bacteria solution, bacteria body and bacterial secretion on calcium carbonate crystal formation. Results showed that the effect was stronger as the concentration of bacteria increasing; the crystals’ form could not be affected by bacteria body only, but the bacterial secretion could induce the formation of polymorphic (e.g. spherical and spindle) metastable vaterite; inorganic-organic composite CaCO₃ film formed under long-term effect by microbe. Based on the results of solution conductivity and FT-IR spectra of CaCO₃ crystals, it could be concluded that there were electrostatic and coordination interaction between polar groups (COOH, C＝O) in protein molecule and Ca^2＋. The results are useful for engineering application, such as repairing micro-crack on concrete surface, protecting old building surface and producing micron and nano calcium carbonate grains.

Key words: biomineralization, carbonate-mineralization microbe, calcium carbonate, organic matter-me- diation