木葡糖酸醋杆菌运动相关基因的敲除及对细菌纤维素合成的影响

Knockdown of motility-related genes of Komagataeibacter xylinus and its effect on bacterial cellulose synthesis

摘要:

细菌纤维素(bacterial cellulose, BC)是由细菌合成的高分子生物聚合物，具有持水性高、结晶度高、纯度高等优良特性，广泛应用于食品、医疗、化妆品和功能膜等领域。木葡糖酸醋杆菌(Komagataeibacter xylinus)是BC合成研究的模式菌株。在细菌中，运动相关基因与BC合成有关，而在木葡糖酸醋杆菌CGMCC 2955中，尚不清楚运动相关基因的功能及其对BC合成的影响。本研究利用λ-Red重组系统敲除细菌运动相关基因motA、motB、mot2A，以此构建了敲除菌株K. x-ΔmotA、K. x-ΔmotB、K. x-Δmot2A及双敲菌株K. x-ΔmotAB。结果表明：敲除菌K. x-ΔmotAB的BC产量最高，达到(5.05±0.26) g/L，与野生型菌株相比，提高24%左右；同时，该菌株合成的BC的孔隙率最低，达到了54.35%，并具有更优越的力学性能，杨氏模量可达5.21 GPa。在木葡糖酸醋杆菌CGMCC 2955中敲除运动相关基因之后，并未降低BC的产量，反而促进了BC的合成，进一步加深了醋酸菌中运动性与BC关系的认知；并且敲除motA和motB基因后，降低了BC的孔隙率并提升了BC的力学性能，为BC合成及膜结构调节改造提供了参考。

Abstract:

Bacterial cellulose (BC) is a biopolymer synthesized by bacteria, which possess excellent characteristics such as high water holding capacity, high crystallinity, and high purity. It is widely used in food, medical, cosmetics, and functional films. Komagataeibacter xylinus is a model strain used in BC synthesis research. In bacteria, motility-related genes are associated with BC synthesis, whereas in Komagataeibacter xylinus CGMCC 2955, the functions of motility-related genes and their effects on BC synthesis are not known. To address this gap, we used the λ Red recombinant system to individually knock out motA, motB, and mot2A respectively, and constructed the knockout strains K. x-ΔmotA, K. x-ΔmotB, and K. x-Δmot2A. Additionally, both motA and motB were disrupted to construct the K. x-ΔmotAB mutant. The results demonstrated that knockout strain K. x-ΔmotAB exhibited the highest BC yield, reaching (5.05±0.26) g/L, which represented an increase of approximately 24% compared to wild-type strains. Furthermore, the BC synthesized by this strain exhibited the lowest porosity, 54.35%, and displayed superior mechanical properties with a Young’s modulus of up to 5.21 GPa. As knocking out motA and motB genes in K. xylinus CGMCC 2955 did not reduce BC yield; instead, it promoted BC synthesis. Consequently, this research further deepened our understanding of the relationship between motility and BC synthesis in acetic acid bacteria. The knockouts of motA and motB genes resulted in reduced BC porosity and improved mechanical properties, provides a reference for BC synthesis and membrane structure regulation modification.