Team:SDSZ China/Description

Description
Inspiration
        Cracks on concrete or stone structures is a major problem threatening the sturdiness of constructions, especially ancient ones, which all have such problems more or less due to continuous exposure to wind, rain and light. As people have greater demand for cultural life and increasing interest in the culture and history of their countries in recent years, the maintenance of ancient structures has become an urgency.
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        In China, however, both technology and the degree of recognition cannot reach the urgent demand. The traditional method of maintenance is grouting or caulking those cracks, but that either requires enlarging the cracks to form a “V” shaped groove or needs to use electric injectors to inject materials for renovation, which leads to a series of problems. For instance, the former one would impose further damage on the surface of those structures, influencing them in aesthetic degree; the later one, on the other hand, has the possibility of damaging structures from the inside due to usage of electric tools.
        In order to improve the current situation, SDSZ China seeks for a better method that can better protect ancient constructions while ensuring their appearances. After research and analysis, our team finds out that using microorganisms to synthesize HAP or silicon dioxide is a better method with high efficiency, safety and environmental friendliness. Compared to traditional approach, the new method doesn’t require enlargement of the cracks, and has little potential threat of structural damage since it doesn’t include electric tools. In addition, this method works under biological regulation, which reduces demand of human power.
Design
        We wanted to bind mineralizing protein to the cytomembrane of E.coli to produce materials needed for construction reservation while making sure that no bacteria leakage would occur. Therefore, our Project includes three section: silicon mineralization, calcium mineralization, and kill switch.
        For silicon mineralization, we wanted to combine Silicatein-pUC57 and ice nucleation protein (INP) genes with the plasmid S010 pET28b-csgA-linker-mfp5-7His (pET). Silicatein-pUC57 produce silicatein, a protein commonly seen in sponge that can produce silicon dioxide. INP is a transmembrane protein to help locate Silicatein-pUC57 outside the cell.
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Fig.3 shows the schematic of INP-silicatein
        For calcium mineralization, we wanted to combine CsgA structural domain (one of the main composite of membrane protein on E.coli) with Msp3S-pep (homologue of protein in the foot of mussels). Msp3S-pep facilitates the synthesis of HAP， which can be used in reservation of HAP-based constructions.
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Fig.4 shows the schematic of csgA-Mfp5.
Fig.5 shows the schematic of csgA-Mfp5-Mfp5.
        TEM would be used to test the results of these two methods.
        Comparing the effectiveness of K1 and K2 kill switches, we chose K1 because K2 showed leakage of toxic protein. Experiments has shown that K1 could meet our needs. By spraying arabinose on the bacteria, they would synthesize toxic protein and kill themselves.
Fig.6
Fig.6 represents the schematic of K1 kill switch.
Reference
[1] 京坤建筑修缮《建筑修缮市场的现状和未来》
[2] RAMAKRISHNAN V，BANG S S，DEO K S. A novel technique for repairing cracks in high performance concrete using bacteria, Proceedings of the International Conference on HPHSC. Perth， Australia:Elsevier，1998:597—618.
[3] WANG J Y，BELIE N，VERSTRAETE W. Diatomaceous earth as a protective vehicle for bacteria applied for self -healing concrete [J]. Journal of Industrial Microbiology & Biotechnology，2012，39 (4):567—577.