Calcium Carbonate Precipitating Cultivable Bacteria from Different Speleothems of Karst Caves

The aim of the study was to reveal and compare microbiota different carbonate speleothems from two epigenic karst regions (Baradla Csodabogyós caves) in Hungary. Stalagmites, stalactites, soda straws, moonmilks, cave wall surfaces dripping waters were sampled plated on subsurface-environment imitating culture media containing low amount nutrients, minerals extract sediments. Diverse oligo-heterotrophic bacterial community composition (192 species phyla Actinobacteria, Proteobacteria, Firmicutes Bacteroidetes) – with hitherto unknown bacteria varied samples. CaCO3 precipitating capacity 126 strains taxonomical positions tested solid B4 medium. 75% precipitated crystals various morphology colonies metabolic tests showed that higher alkalizing activity led rate precipitation mucoid colonies. Scanning electron microscopy, high-resolution transmission microscopy X-ray diffraction analysis indicated precipitates dominated by calcite, nanosize vaterite identified for Paeniglutamicibacter kerguelensis (strain BaSD-225). Our suggests proteolytic are widespread biofilms caves these can actively contribute formation through their microenvironment.