Effects of microbially induced carbonate precipitation on soil bacterial communities and predictions of phenotypic and functional characteristics

Microbially induced carbonate precipitation (MICP) is widely used for soil stabilization; however, its long-term impact on bacterial community structure and function remains unclear. In this study, we investigated the regulatory mechanisms of MICP on soil physicochemical properties and microbial communities by spraying Sporosarcina pasteurii and cementation solutions (urea + CaCl₂), combined with high-throughput sequencing, phenotypic prediction, and genomic functional analysis. The results demonstrated that MICP significantly increased soil pH (from 7.62 to 7.94), alkali-hydrolyzable nitrogen (AHN: from 67 to 1 603 mg·kg⁻¹), exchangeable calcium (from 10.4 to 30.6 mg·kg⁻¹), and chloride ion concentration (from 377 to 26 679 mg·kg⁻¹), whereas induced calcium carbonate deposition. The Shannon diversity index decreased significantly and the microbial community structure converged. The relative abundances of Firmicutes and Bacteroidetes increased from 3.31% and 1.68% to 12.73% and 6.78%, respectively, whereas those of Proteobacteria and Actinobacteria decreased from 48.56% and 25.53% to 41.61% and 19.17%, respectively. Core functional taxa, including Lysobacter and Sporosarcina, were significantly enriched and driven by biofilm formation, urease activity, and salt-alkali tolerance gene expression. Redundancy analysis and network topology revealed that Ca²⁺, AHN, and pH formed the driving framework for community differentiation, accounting for 66.51% of variation. Functional predictions indicated suppressed core metabolic pathways (e.g., DNA replication and energy metabolism; reduced by 15%–35%) but enhanced biofilm formation and stress-resistant phenotypes in the MICP group. This study demonstrates that MICP screens for stress-resistant functional bacteria in a high-calcium, high-chloride, and alkaline environment but may sacrifice the diversity of soil ecological functions. These findings provide a theoretical basis for ecological risk assessment and process optimization of MICP technology.