BACKGROUND The ureolytic bacterium Sporosarcina pasteurii is well-known for its capability of microbially induced calcite precipitation (MICP), representing a great potential in constructional engineering and material applications. However, the molecular mechanism for its biomineralization remains unresolved, as few studies were carried out. RESULTS The addition of urea into the culture medium provided an alkaline environment that is suitable for S. pasteurii. As compared to S. pasteurii cultivated without urea, S. pasteurii grown with urea showed faster growth and urease production, better shape, more negative surface charge and higher biomineralization ability. To survive the unfavorable growth environment due to the absence of urea, S. pasteurii up-regulated the expression of genes involved in urease production, ATPase synthesis and flagella, possibly occupying resources that can be deployed for MICP. As compared to non-mineralizing bacteria, S. pasteurii exhibited more negative cell surface charge for binding calcium ions and more robust cell structure as nucleation sites. During MICP process, the genes for ATPase synthesis in S. pasteurii was up-regulated while genes for urease production were unchanged. Interestingly, genes involved in flagella were down-regulated during MICP, which might lead to poor mobility of S. pasteurii. Meanwhile, genes in fatty acid degradation pathway were inhibited to maintain the intact cell structure found in calcite precipitation. Both weak mobility and intact cell structure are advantageous for S. pasteurii to serve as nucleation sites during MICP. CONCLUSIONS Four factors are demonstrated to benefit the super performance of S. pasteurii in MICP. First, the good correlation of biomass growth and urease production of S. pasteurii provides sufficient biomass and urease simultaneously for improved biomineralization. Second, the highly negative cell surface charge of S. pasteurii is good for binding calcium ions. Third, the robust cell structure and fourth, the weak mobility, are key for S. pasteurii to be nucleation sites during MICP.

中文翻译：

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尿素分解细菌巴斯德孢霉菌生物矿化的有利因素。

背景技术解尿细菌巴斯德孢子菌（Sporosarcina pasteurii）以其微生物诱导方解石沉淀（MICP）的能力而闻名，在建筑工程和材料应用中具有巨大潜力。然而，由于进行了很少的研究，其生物矿化的分子机制仍未解决。结果向培养基中添加尿素提供了适合于巴氏酵母的碱性环境。与不使用尿素种植的巴氏酵母相比，用尿素种植的巴氏酵母显示出更快的生长和脲酶生产，更好的形状，更多的负表面电荷和更高的生物矿化能力。为了在没有尿素的情况下生存在不利的生长环境中，巴氏酵母可上调与尿素酶生产，ATPase合成和鞭毛有关的基因的表达，可能会占用可用于MICP的资源。与非矿化细菌相比，巴斯德氏酵母显示出更多的细胞表面负电荷以结合钙离子，并且细胞结构更坚固，成为成核位点。在MICP过程中，巴斯德氏酵母中ATPase合成的基因被上调，而脲酶生产的基因则保持不变。有趣的是，参与鞭毛的基因在MICP过程中被下调，这可能导致巴氏链球菌流动性差。同时，脂肪酸降解途径中的基因被抑制以维持在方解石沉淀中发现的完整细胞结构。弱迁移率和完整的细胞结构均有利于巴氏链球菌在MICP期间用作成核位点。结论证实了四个因素有利于巴氏链球菌在ICP中的超级性能。首先，巴氏酵母的生物质生长与脲酶生产的良好相关性同时提供了充足的生物质和脲酶，以改善生物矿化作用。第二，巴氏酵母的细胞表面高度负电荷对结合钙离子有好处。第三，鲁棒的细胞结构和第四，弱的迁移率是巴氏链球菌成为MICP过程中成核位点的关键。