枯草芽孢杆菌中多聚-γ-谷氨酸的生物合成及其调控机制

Biosynthesis of Poly-γ-glutamic Acids and Relevant Regulatory Networks in Bacillus subtilis

芽孢杆菌属(Bacillus)细菌及少数其他细菌可产生多聚-γ-谷氨酸(Poly-γ-glutamic acids,缩写为γ-PGA),这是一类可溶、能降解、有多种用途的生物高分子材料,这种高分子物质还参与某些细菌的荚膜形成.PGA合成酶复合体与细胞质膜相连,在枯草芽孢杆菌(包括纳豆菌)和炭疽菌中分别由pgsBCAE和capBCADE基因簇编码.在枯草芽孢杆菌中pgsBCAE的表达和γ-PGA生物合成受到群体感应(Quorum sensing)系统及其它信号转导途径构成的复杂网络所调控,与细菌芽孢形成、自然感受态诱导、次生代谢物质合成和群聚运动等重要过程相互关联,共同对芽孢杆菌的环境适应和生存发挥着关键的作用.本文总结和评述了芽孢杆菌γ-PGA生物合成及相关调控机制研究的新进展,特别是信号转导网络中两个小分子多肽DegQ和SwrA的功能.这两个小分子介导群体感应系统和DegS-DegU二组分系统之间的相互作用,共同调控γ-PGA的生物合成.对PGA合成调控机制的了解可为γ-PGA高产工程菌株的构建和生产工艺设计等提供参考.

The poly-y-glutamic acids （7-PGA）, a group of biocompatible, biodegradable and soluble macromolecular biopolymers of multiple uses in food, cosmetics, medicine and environmental protection, are synthesized by Bacillus species and a few other Gram-positive bacteria. PGA is also the main component of capsules of certain bacteria such as B. anthracis. The PGA synthetase complex is cytomembrane-associated and encoded by the gene cluster ofpgsBCAE in B. subtilis and capBCAE in B. anthracis, respectively, In B, subtilis, the transcription ofpgsBCAE and biosynthesis of PGA are regulated by the quorum sensing systems and other regulators which form a complex regulatory network. The cellular processes of PGA biosynthesis, natural competence, synthesis of bioactive secondary metabolites, sporulation, and swarming are interconnected and together play a central role in the bacterial adaptation to environmental changes and survival. This review introduced the progress in the study of PGA biosynthesis and relevant signal transduction and regulatory pathways, focusing on the cellular functions of two small regulatory polypeptides, DegQ and SwrA. The two small peptides mediate the interactions between the quorum sensing systems and the DegS-DegU two-component system, which directly controls the biosynthesis of PGA. Some insights are provided for the applications such as development of high yield strains and fermentation strategies for PGA loroduction. Fig 3, Ref48