Calcium carbonate precipitation by bacterial strains isolated from limestone cave and from loamy soil

o 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 pptn., and the type of crystals formed were detd. at incubation temps. of 4, 22, and 32°C. The highest of these temps. favored CaCO3 formation. Most of the bacteria pptd. 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 pptn. of carbonates is discussed. Further expts. are in progress in order to select the most suitable bacterial strains for a controlled prodn. of calcareous crusts.