State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210096, Jiangsu, People's Republic of China.
Microb Cell Fact. 2020 Jan 23;19(1):12. doi: 10.1186/s12934-020-1281-z.
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.
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.
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.
脲酶细菌巴氏固氮菌以其微生物诱导碳酸钙沉淀（MICP）的能力而闻名，这在建筑工程和材料应用中具有巨大的潜力。然而，由于很少有研究开展，其生物矿化的分子机制仍未得到解决。
在培养基中添加尿素为巴氏固氮菌提供了适合的碱性环境。与未添加尿素培养的巴氏固氮菌相比，添加尿素培养的巴氏固氮菌生长更快，产脲酶能力更强，形态更好，表面负电荷更高，生物矿化能力更强。为了在没有尿素的情况下生存，巴氏固氮菌上调了与产脲酶、ATP 酶合成和鞭毛相关的基因表达，可能抢占了可用于 MICP 的资源。与非矿化细菌相比，巴氏固氮菌的细胞表面负电荷更有利于结合钙离子，细胞结构更坚固，作为成核点。在 MICP 过程中，巴氏固氮菌的 ATP 酶合成基因上调，而产脲酶基因不变。有趣的是，在 MICP 过程中，与鞭毛相关的基因下调，这可能导致巴氏固氮菌的移动性变差。同时，脂肪酸降解途径的基因受到抑制，以维持碳酸钙沉淀中发现的完整细胞结构。移动性差和细胞结构完整有利于巴氏固氮菌在 MICP 过程中充当成核点。
有四个因素有利于巴氏固氮菌在 MICP 中表现出优异的性能。首先，巴氏固氮菌生物量增长和产脲酶之间的良好相关性同时为提高生物矿化提供了足够的生物量和脲酶。其次，巴氏固氮菌的高负表面电荷有利于结合钙离子。第三，坚固的细胞结构和第四，较弱的移动性，是巴氏固氮菌在 MICP 过程中成核点的关键。
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