The up-regulation of carbonic anhydrase genes of <i>Bacillus mucilaginosus</i> under soluble Ca²⁺ deficiency and the heterologously expressed enzyme promotes calcite dissolution

Molecular mechanisms and gene regulation are of interest in the area of geomicrobiology in which the interaction between microbes and minerals is studied. This paper focuses on the regulation of the expression of carbonic anhydrase (CA) genes in <i>Bacillus mucilaginosus</i> and the effects of the expression product of the <i>B. mucilaginosus</i> CA gene in <i>Escherichia coli</i> on calcite weathering. Real-time fluorescent quantitative PCR (RT-qPCR) was used to explore the relationship between CA gene expression in <i>B. mucilaginosus</i> and promotion of calcite dissolution under condition of Ca²⁺ deficiency. The results showed that adding calcite to the medium, which lacks Ca²⁺, can up-regulate the expression of the bacterial CA genes to accelerate calcite dissolution for bacterial growth. CA genes from <i>B. mucilaginosus</i> were transferred into <i>E. coli</i> by cloning. We then employed crude enzyme extract from the resultant <i>E. coli</i> strain in calcite dissolution experiments. The enzyme extract promoted calcite dissolution. These findings provide direct evidence for the role of microbial CA on mineral weathering and mineral nutrition release.