Profiling of Bacteria Capable of Precipitating CaCO3 on the Speleothem Surfaces in Dupnisa Cave, Kırklareli, Turkey

Abstract

This study aimed to identify the bacteria which take part in the CaCO3 precipitation on the speleothem surfaces of Dupnisa Cave. In addition, this study highlighted the CaCO3 precipitation ability of the bacteria with negative urease activity. 150 isolates with microbial induced calcium carbonate precipitation features were selected and identified. They were belonging to Proteobacteria (53.3%), Firmicutes (32.7%) and, Actinobacteria (4.7%) phyla. The dominant bacterial species on all surface samples were Bacillus mycoides (9.3%), Bacillus zhangzhouensis (5.3%), and Serratia quinivorans (4%). Our results showed that most of the bacteria which can precipitate calcium carbonate on the B4 medium at the first 3 days, have urease negative activity. Within this study, it has been emphasized that other mechanisms enabling the precipitation of CaCO3 besides the urease mechanism should also be investigated. EDS analyses confirmed that the crystals were predominantly composed of calcium, carbon, and oxygen. In addition, the EDS highlighted that the two strains of Bacillus mycoides, isolated from two different surfaces, produced crystals of different morphology. Our study results to the identification of the bacteria which contribute to the Dupnisa Cave walls formation. Besides, our results showed that the Dupnisa Cave is housing bacteria with biotechnological and engineering applications potentials.