Characterization and genome analysis of Neobacillus mesonae NS-6, a ureolysis-driven strain inducing calcium carbonate precipitation.

In this study, a highly promising bacterium was isolated from sandstone oil in the Ordos Basin, named strain NS-6 which exhibited exceptional urease production ability and demonstrated superior efficiency in inducing the deposition of calcium carbonate (CaCO ₃ ). Through morphological and physiochemical characteristics analysis, as well as 16S rRNA sequencing, strain NS-6 was identified as Neobacillus mesonae . The activity of urease and the formation of CaCO ₃ increased over time, reaching a maximum of 7.9 mmol/L/min and 184 mg (4.60 mg/mL) respectively at 32 h of incubation. Scanning Electron Microscopy (SEM) revealed CaCO ₃ crystals ranging in size from 5 to 6 μm, and Energy Dispersive X-ray (EDX) analysis verified the presence of calcium, carbon, and oxygen within the crystals. X-ray Diffraction (XRD) analysis further confirmed the composition of these CaCO ₃ crystals as calcite and vaterite. Furthermore, the maximum deposition of CaCO ₃ by strain NS-6 was achieved using response surface methodology (RSM), amounting to 193.8 mg (4.845 mg/mL) when the concentration of calcium ions was 0.5 mmol/L supplemented with 0.9 mmol/L of urea at pH 8.0. Genome-wide analysis revealed that strain NS-6 possesses a chromosome of 5,736,360 base pairs, containing 5,442 predicted genes, including 3,966 predicted functional genes and 1,476 functionally unknown genes. Genes like ure A, ure B, and ure C related to urea catabolism were identified by gene annotation, indicating that strain NS-6 is a typical urease-producing bacterium and possesses a serial of genes involved in metabolic pathways that mediated the deposition of CaCO ₃ at genetic level.
Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
(Copyright © 2023 Xu, Zhang, Ma, Rao and Ma.)