Calcium Carbonate Precipitation by Bacterial Strains Isolated from a Limestone Cave and from a Loamy Soil

To study the role of calcifying bacteria in monument protection, 31 calcifying bacterial strains were isolated from natural habitats: 64% were of the genus Bacillus , 16% of the genus Arthrobacter , and 2 of the remaining isolates were identified as Kingella and Xanthomonas . The ability to form CaCO 3 crystals, the extent of the precipitation, and the type of crystals formed were determined at incubation temperatures of 4, 22, and 32°C. The highest of these temperatures favored CaCO 3 formation. Most of the bacteria precipitated CaCO 3 in the form of calcite. This activity was strictly controlled by the growth of microbial colonies on a solid substrate. The role of the calcifying bacteria in natural precipitation of carbonates is discussed. Further experiments are in progress in order to select the most suitable bacterial strains for a controlled production of calcareous crusts.