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 CaCO3 crystals, the extent of the precipitation, and the type of crystals formed were determined at incubation temperatures of 4, 22, and 32 degreesC. The highest of these temperatures favored CaCO3 formation. Most of the bacteria precipitated CaCO3 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.