全基因测序发现ε-聚赖氨酸产生菌卡特利链霉菌具有两个大的线性复制子，包括一个新的、携带了丰富次生代谢物合成基因的1.8 Mb巨型质粒。ε-聚赖氨酸通常是由25~35个L-赖氨酸通过α-羧基和ε-氨基的酰胺键连接而成，是一种无毒害的新型生物防腐剂和天然材料。卡特利链霉菌染色体和质粒各编码一个ε-聚赖氨酸合成酶。为对接市场对单一聚合度ε-聚赖氨酸的产品需求，本项目拟以阐明ε-聚赖氨酸生物合成机制为切入点，对卡特利链霉菌进行基因组挖掘。一方面，通过产不同链长ε-聚赖氨酸的合成酶的比较分析、功能域置换和关键位点突变，解析ε-聚赖氨酸生物合成过程中控制聚合度的分子机制，人工构建产单一聚合度ε-聚赖氨酸的突变株。另一方面，鉴定卡特利链霉菌的新型端粒-末端蛋白系统，消除巨型线性质粒，以期提高工程菌的生长速度和发酵性能。

ε-Poly-L-lysine (ε-PL) is an antimicrobial homopolymer of L-lysine via isopeptide bond synthesized by the ε-PL synthetase (Pls), and can be used as a pollution-free food preservative. A short chain length ε-PL producer Streptomyces cattleya DSM46488 had been completely sequenced. Interestingly, two linear giant replicons were found in S. cattleya, of which a novel linear plasmid with the size of 1.8 Mb carries a large number of gene clusters for the potential production of secondary metabolites. Two homologous genes of NRPS-like Pls were idetnified in the individual replicons. In this proposal, I am elucidating the control mechanism of the degree of polymerization of ε-PL by genome mining of S. cattleya. Combinatorial and mutational analysis of the functional domains will be performed to the different ε-PL synthetases, which produced the ε-PL with diverse polymerization degrees. I will design and develop an engineered strain that is able to produce the ε-PL with the unique polymerization degree. In addition, if the giant plasmid could be cured from the strain, the small chromosome of S. cattleya may be a very interesting vehicle for the ε-PL biosynthesis.