| Abstrakt: |
Moonmilk is a secondary calcite deposit, mainly composed of fine calcium carbonate crystals (CaCO3), with different morphology and textures ranging from pasty, muddy, powdery to hard, depending on the water content. These karstic speleothems formed of calcite nanofibers in which the contribution of biotic rock-building processes is presumed to involve indigenous microorganisms. Although its biogenic origin is widely accepted, the mechanism of production of calcite nanofibers has not been fully elucidated. Cave moonmilk deposits found in karst caves host an abundant and diverse actinobacterial population that has a great potential for producing novel natural bioactive compounds. Microorganisms, mostly bacteria that are able to dissolve rock or induce mineral precipitation could be used in the construction industry and engineering. Crystallization and formation mechanism of calcium carbonate nanostructures are of high interest in different fields, such as geomicrobiology (rock-microbes interactions), astrobiology (biosignatures), medicine and pharmacy (antibiotics and bioactive compounds), nanotechnology (calcium carbonate nanofibers) but also archeology (necropoleis). Here we present the mineralogical profiling using X-ray powder diffraction (Bruker D8 ADVANCE) demonstrated that calcite was the dominant mineral in majority of speleothemes with a few variations in the elemental components. Morphological characterization of different phases of crystallization of the moonmilk was shown using scanning electron microscopy (JEOL JSM IT 200 LA). The content of nine heavy metals (Co, Mn, Ni, Cu, Fe, Zn, Cd, Cr and Pb), through two sample readings, was determined by flame atomic absorption spectrometry (Varian 240 FS). Considering the exceptional microbiological diversity of karst caves, intensive multidisciplinary research will contribute to the discovery of new bioactive molecules with a focus on antimicrobial compounds. [ABSTRACT FROM AUTHOR] |
