Microorganisms from ancient unique structures: physiology, genetics, application prospects

Bioconcrete is a material that incorporates specific bacterial species along with several additional components beyond those found in conventional concrete. Due to microbially induced calcium carbonate precipitation (MICP), it has the ability to prevent the propagation of microcracks and to seal them. The bacterial strains employed must remain viable under the harsh conditions of concrete formation, which include high pH, low moisture content, high density, and elevated temperature during curing. It has been hypothesized that bacteria capable of surviving for centuries within ancient construction materials may possess properties advantageous for bioconcrete applications. In this study, viable bacterial spores were isolated from fragments of ancient mortar collected from the ruins of the ancient city of Chersonesus Taurica. This site, a unique monument of Greek architecture that existed until the 15th century AD, is located in the area of modern Sevastopol (Russia). The isolated strains were evaluated for their ability to grow at pH 10, to produce urease, to precipitate calcium carbonate, and to withstand the concrete processing cycle. Genomic sequencing was performed for three selected promising alkalophilic strains. One of them was identified as a potential representative of a previously undescribed species, Sutcliffiella sp., while the other two were identified as Cytobacillus horneckiae (all belonging to the family Bacillaceae). Genomic analysis revealed a set of genes associated with carbonate ion production and resistance to alkaline environments.