Distribution of ε-Poly-L-lysine Synthetases in Coryneform Bacteria Isolated from Cheese and Human Skin

ε-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 NRPS-like enzyme called Pls. Here 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 ε-poly-L-lysine. A comprehensive sequence analysis suggests 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 ε-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. ε-poly-L-lysine has potent, wide spectrum of inhibitory activity and is heat stable and biodegradable. It has been approved for food preservation by an increasing number of countries. ε-poly-L-lysine is produced from the soil bacteria Streptomyces, also a producer 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 ε-poly-L-lysine may naturally exist in cheese and on our skin, and ε-poly-L-lysine producers are not limited to filamentous actinobacteria.