Effect on calcium carbonate morphology by a strain of rock actinomycete

Abstract:

[Objective] Microbes-induced mineralization is one of the hottest issues in the field of geomicrobiology. Strain DHS C013^T isolated from the surfaces of rocks in the Karst region was used to investigate microbial influence on the formation of carbonate and its morphology in the metallogenic system consisting NaHCO₃ and Ca(NO₃)₂·4H₂O. [Methods] Strain DHS C013^T was inoculated into malt extract-glucose-yeast extract peptone (MGYP) liquid medium. After cultivation we put the fermented solution, supernatant, hypha pellets, sterile MGYP liquid medium and ultrapure water into the metallogenic system separately. Scanning electronic microscope was applied to observe the crystals at the bottom of the petri dishes. [Results] In the metallogenic system with ultrapure water, only standard calcite of rhombohedron was found. However, special morphology of CaCO₃, such as dumbbelllike, spherulite and scaly cylindrical shapes, were found in the metallogenic system with actinomycetes, hyphae fragment and their cell metabolism products. These calcium carbonates of special morphology might be resulted from their nucleation on smaller hypha pellets, hyphae fragment or extracellular secretion. [Conclusion] Actinomycetes can induce the formation of CaCO₃, and the mycelium and metabolites have important effects on regulating and influencing CaCO₃ morphology. Our data provide new evidence for further understanding of the biological mineralization mediated by actinomycete and its metabolic products.