Adaptive Evolution of Sporosarcina pasteurii Enhances Saline-Alkali Resistance for High-Performance Concrete Crack Repair via MICP

Abstract

Microbially induced calcium carbonate precipitation (MICP) has emerged as a research focus in concrete crack remediation due to its environmental compatibility and efficient mineralization capacity. The hypersaline conditions of seawater (average 35 g/L NaCl) and alkaline environments (pH 12) within concrete cracks pose significant challenges to the survival of mineralization-capable microorganisms. To enhance microbial tolerance under these extreme conditions, this study employed a laboratory adaptive evolution strategy to successfully develop a Sporosarcina pasteurii strain demonstrating tolerance to 35 g/L NaCl and pH 12. Comparative analysis of growth characteristics (OD₆₀₀), pH variation, urease activity, and specific urease activity revealed that the evolved strain maintained growth kinetics under harsh conditions comparable to the parental strain under normal conditions. Subsequent evaluations demonstrated the evolved strain's superior salt-alkali tolerance through enhanced enzymatic activity, precipitation yield, particle size distribution, crystal morphology, and microstructure characterization under various saline-alkaline conditions. Whole-genome sequencing identified five non-synonymous mutated genes associated with ribosomal stability, transmembrane transport, and osmoprotectant synthesis. Transcriptomic profiling revealed 1082 deferentially expressed genes (543 upregulated, 539 downregulated), predominantly involved in ribosomal biogenesis, porphyrin metabolism, oxidative phosphorylation, tricarboxylic acid (TCA) cycle, and amino acid metabolism. In concrete remediation experiments, the evolved strain achieved superior performance with 89.3% compressive strength recovery and 48% reduction in water absorption rate. This study elucidates the molecular mechanisms underlying S. pasteurii's salt-alkali tolerance and validates its potential application in the remediation of marine engineering.

Keywords: MICP; Sporosarcina pasteurii; anti permeability; compressive strength; genome; laboratory adaptive evolution; transcriptome.

Figure 1

Adaptive evolutionary approach to the laboratory.

Figure 2

Salt stress tolerance results (a) and alkali stress tolerance results (b) of S. pasteurii.

Figure 3

Laboratory adaptive evolution process of salt-stressed S. pasteurii OD₆₀₀ (a), pH (b), urease activity (c), unit urease activity (d).

Figure 4

Laboratory adaptive evolution process of salt-tolerant S. pasteurii under alkali stress OD₆₀₀ (a), pH (b), urease activity (c), unit urease activity (d).

Figure 5

Comparison of OD₆₀₀ and pH (a), urease activity and unit urease activity (b) between the original strain (OS) and the evolved strain (ES) of S. pasteurii under stress-free and stress conditions (pH = 12, NaCl 35 g/L).

Figure 6

The precipitation amount of mineralized products and the utilization rate of calcium ions (a), the particle size of the precipitate (b), the XRD (c: the crystal form of calcium carbonate is calcite, v: the crystal form of calcium carbonate is vaterite) of the precipitate (c), the SEM of the precipitate produced by the mineralization reaction of the evolved strain (d), and the SEM of the precipitate produced by the mineralization reaction of the original strain (e).

Figure 7

Changes in gene expression of heme and coenzyme B12 synthesis pathways.

Figure 8

Gene expression changes in the oxidative phosphorylation pathway. (The arrows represent the transport and conversion processes of different ions in the channels of oxidative phosphorylation).

Figure 9

Changes in gene expression of tricarboxylic acid cycle and amino acid pathway.

Figure 10

Morphological characteristics and performance evaluation of bacterial-based concrete repair: (a) pre-repair concrete specimen; (b) post-repair specimen using evolved strain; (c) post-repair specimen using original strain; (d) water absorption rate; (e) compressive strength variation.