Deposition of calcium carbonate in karst caves: role of bacteria in Stiffe's Cave

Authors

Claudia Ercole, University of L'AquilaFollow
Paola Cacchio, University of L'Aquila
Giorgio Cappuccio, Istituto per lo Studio dei Materiali Nanostrutturati
Aldo Lepidi, University of L'Aquila

Abstract

Bacteria make a significant contribution to the accumulation of carbonate in severa! natural habitats where large amounts of carbonates are deposited. However, the role played by microbial communities in speleothem formation (stalactites, stalagmites etc.) in caves is still unclear. In bacteria carbonate is formed by autotrophic pathways, which deplete CO₂ from the environment, and by heterotrophic pathways, leading to active or passive precipitation. We isolated cultivable heterotrophic microbial strains, able to induce CaCO₃ precipitation in vitro, from samples taken from speleothems in the galleries of Stiffe’s cave, L’Aquila, Italy. We found a large number of bacteria in the calcite formations (1 x 10⁴ to 5 x 10⁹ cells g^-1). Microscopic examination, in laboratory conditions at different temperatures, showed that most of the isolates were able to form calcium carbonate microcrystals. The most crystalline precipitates were observed at 32°C. No precipitation was detected in un-inoculated controls media or in media that had been inoculated with autoclaved bacterial cells. X-ray diffraction (XRD) analysis showed that most of the carbonate crystals produced were calcite. Bacillus strains were the most common calcifying isolates collected from Stiffe’s Cave. Analysis of carbonate-solubilization capability revealed that the non-calcifying bacteria were carbonate solubilizers.

DOI

http://dx.doi.org/10.5038/1827-806X.30.1.6

Recommended Citation

Ercole, Claudia; Paola Cacchio; Giorgio Cappuccio; and Aldo Lepidi. 2001. Deposition of calcium carbonate in karst caves: role of bacteria in Stiffe's Cave. International Journal of Speleology, 30: 69-79.
Available at: https://digitalcommons.usf.edu/ijs/vol30/iss1/6