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

The poly-γ-glutamic acids (γ-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 of pgsBCAE in B. subtilis and capBCAE in B. anthracis, respectively. In B. subtilis, the transcription of pgsBCAE 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 production. Fig 3, Ref 48