Transcriptional regulation of the lantibiotic structural gene from bifidobacterium longum DJO10A

Abstract

Bifidobacterium longum DJO10A produces a lantibiotic, but only during growth on agar media. A quantitative real-time PCR assay targeting its lanA gene was developed and revealed that the gene was up-regulated more than nine-fold on agar than in broth. A crude lantibiotic preparation revealed a broad spectrum of inhibition. Addition of this extract to broth cultures of B. longum DJO10A induced lanA gene expression in a dose-dependent and log-phase fashion. Sub-inoculation using > 10% of an induced broth culture maintained lanA expression. The inducer is most likely the lantibiotic itself, given that a ~ 3.2 kDa peak corresponding to the predicted size for the lantibiotic, was attached to the cell surface. A predicted repressor gene lanRI was codon optimized and expressed in vitro. Purification of this protein will further our understanding of its function and facilitate the development of strategies to enable production of this lantibiotic in broth.