title: Investigation on the effects of ϵ-poly-L-lysine on a producing strain Streptomyces ahygroscopicus GIM8, for better understanding its biosynthesis.
abstract: ϵ-Poly-L-lysine (ϵ-PL) is an L-lysine homopolymer with strong antimicrobial activity, which is generally produced by Streptomyces strains. ϵ-PL is only produced under acidic conditions in liquid culture, and to improve the current understanding of ϵ-PL biosynthesis, the present study was undertaken to investigate the effects of ϵ-PL on its producer Streptomyces ahygroscopicus GIM8, under acidic and neutral conditions. The results indicated that a neutral pH favored ϵ-PL adsorption onto the cells, whereas minimal adsorption occurred at pH 4.0, the maximum pH for ϵ-PL production. At pH 7.0, small amounts of ϵ-PL caused considerable ATP leakage from the cells, which showed increased membrane permeability. Conversely, ATP leakage was inhibited by ϵ-PL at pH 4.0. Transmission electron microscopy investigation indicated that the cytoplasmic membrane was the primary site of ϵ-PL activity at pH 7.0, and that cell shape was maintained. Metabolic activity profiles revealed that ϵ-PL decreased cellular metabolic activity at a relatively low rate at pH 7.0. However, the toxic effect was significantly enhanced at pH 4.0. Based on these data, a mechanism for the effect of ϵ-PL on ϵ-PL-producing cells under neutral and acidic conditions is proposed. Additionally, acidic conditions may potentially be required for ϵ-PL biosynthesis in liquid culture because low pH can increase membrane permeability and prevent binding of ϵ-PL onto cells, both of which favor the secretion of the ϵ-PL produced by the cells into the broth. This research contributes to the current understanding of ϵ-PL biosynthesis.
authors.affiliation: Guangdong Institute of Microbiology, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Ministry-Guangdong Province Jointly State Key Laboratory of Applied Microbiology, Guangzhou, China; Department of Biology, Ningde Normal University, Ningde, China.
authors.forename: Sheng-Rong
authors.initials: SR
authors.lastname: Liu
authors.forename: Qing-Ping
authors.initials: QP
authors.lastname: Wu
authors.forename: Ju-Mei
authors.initials: JM
authors.lastname: Zhang
authors.forename: Shu-Ping
authors.initials: SP
authors.lastname: Mo
authors.forename: Chun
authors.initials: C
authors.lastname: Xiao
authors.forename: Xiao-Juan
authors.initials: XJ
authors.lastname: Yang
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000327:Adsorption; D002462:Cell Membrane / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D046529:Microscopy, Electron, Transmission; D011107:Polylysine / Q000096:biosynthesis* / Q000633:toxicity; D013302:Streptomyces / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D011107:Polylysine; D000255:Adenosine Triphosphate
keywords: Antimicrobial; Biosynthesis; Fermentation; Homopolymer; Streptomyces ahygroscopicus; ϵ-Poly-L-lysine