Microorganisms involved in the formation and dissolution of carbonate deposits in spanish caves

Abstract

Microorganisms play critical roles in biogeochemical processes. In caves, carbonate deposition constitutes a common process. Although microorganisms able to induce these deposits have been previously reported, little information is available on the microorganisms involved, their activity, and the conditions required for the process to occur. This study presents results on the induction of carbonate precipitation and dissolution by microorganisms. RNA-based molecular fingerprinting procedures were used for profiling the metabolically active bacterial communities involved in the preliminary stages of moonmilk deposits. Bacteria were cultured and isolated to analyze the required conditions and nutrients inducing these depositions. Bacteria were able to differentially induce carbonate precipitation depending on the nutrients available for growth. In addition, similar microorganisms can be involved in precipitation and dissolution of carbonates mainly depending on the available nutrient sources. These results suggest the existence of an active carbon cycling process in caves dominated by microorganisms.