MICROBIAL COMMUNITIES OF KARST CAVES

Special geochemical, hydrological and microclimatic conditions in karst caves lead to the development of unique bacterial communities in them. The microbiota of such communities has complex, often unique mechanisms of interaction, which currently does not allow us to fully identify their species composition. Among the bacteria in caves, the most common are representatives of Alfaproteobacteria, Betaproteobacteria, Gammaproteobacteria and Actinobacteria. Lack of light, lack of nutrients and low temperatures lead to a number of adaptations in bacteria, such as a decrease in cell size, slow metabolism, changes in membrane lipids and enzymes, and a number of others. In aphotic conditions, the basis of trophic chains are chemolithotrophic bacteria. The development of bacteria occurs mostly on the surface of mineral formations, soil, walls and in the upper layer of water. Rocky surfaces of caves represent the largest areas potentially suitable for colonization by microbial communities. There is a widespread assumption among researchers that the bacteria living on the walls are mostly cave microbiota and are the least susceptible to changes under anthropogenic load. Bacteria are actively involved in the geochemical transformations of the environment: corrosion of rocks the subsequent deposition of mineral formations. At present, the hypothesis of biogenic mineralization is generally accepted. On the one hand, crystal formation occurs with the participation of only living microorganisms, on the other hand, a change in the physicochemical conditions of the environment is of no small importance in this process. A significant role, according to researchers, is played by secreted extracellular substances that induce passive mineralization or, conversely, cause the dissolution of calcite. In addition, it is known that microorganisms isolated from caves, while remaining viable, after some time lose their ability to form or destroy mineral formations. Bacteria involved in the transformation of mineral substrates are not confined to taxonomic groups and act as part of multispecies communities.