High-level gene expression in Lactobacillus plantarum using a pheromone-regulated bacteriocin promoter

Aims: To use promoters and regulatory genes involved in the production of the bacteriocin sakacin P to obtain high-level regulated gene expression in Lactobacillus plantarum. Methods and Results: In a plasmid containing all three operons naturally involved in sakacin P production, the genes encoding sakacin P and its immunity protein were replaced by the aminopeptidase N gene from Lactococcus lactis (pepN) or the beta-glucuronidase gene from Escherichia coli (gusA). The new genes were precisely fused to the start codon of the sakacin P gene and the stop codon of the immunity gene. This set-up permitted regulated (external pheromone controlled) overexpression of both reporter genes in L. plantarum NC8. For PepN, production levels amounted to as much as 40% of total cellular protein. Conclusions: Promoters and regulatory genes involved in production of sakacin P are suitable for establishing inducible high-level gene expression in L. plantarum. Significance and Impact of the Study: This study describes a system for controllable gene expression in lactobacilli, giving some of the highest expression levels reported so far in this genus.