Distribution of ε-Poly-l-Lysine Synthetases in Coryneform Bacteria Isolated from Cheese and Human Skin

Abstract

epsilon-Poly-L-lysine is a potent antimicrobial produced through fermentation of Streptomyces and used in many Asian countries as a food preservative. It is synthesized and excreted by a special nonribosomal peptide synthetase (NRPS)-like enzyme called Pls. In this study, we discovered a gene from cheese bacterium Corynebacterium variabile that showed high similarity to the Pls from Streptomyces in terms of domain architecture and gene context. By cloning it into Streptomyces coelicolor with a Streptomyces albulus Pls promoter, we confirmed that its product is indeed epsilon-poly-L-lysine. A comprehensive sequence analysis suggested that Pls genes are widely spread among coryneform actinobacteria isolated from cheese and human skin; 14 out of 15 Brevibacterium isolates and 10 out of 12 Corynebacterium isolates contain it in their genomes. This finding raises the possibility that epsilon-poly-L-lysine as a bioactive secondary metabolite might be produced and play a role in the cheese and skin ecosystems. IMPORTANCE Every year, microbial contamination causes billions of tons of food wasted and millions of cases of illness. epsilon-Poly-L-lysine has potent, wide-spectrum inhibitory activity and is heat stable and biodegradable. It has been approved for food preservation by an increasing number of countries. epsilon-Poly-L-lysine is produced from soil bacteria of the genus Streptomyces, also producers of various antibiotic drugs and toxins and not considered to be a naturally occurring food component. The frequent finding of pls in cheese and skin bacteria suggests that epsilon-poly-L-lysine may naturally exist in cheese and on our skin, and epsilon-poly-L-lysine producers are not limited to filamentous actinobacteria.