Heterologous Expression of Thuricin CD Immunity Genes in Listeria monocytogenes

Abstract

ABSTRACTBacteriocins are ribosomally synthesized peptides that can have a narrow or broad spectrum of antimicrobial activity. Bacteriocin producers typically possess dedicated immunity systems that often consist of an ATP-binding cassette (ABC) transporter system and/or a dedicated immunity protein. Here we investigated the genes responsible for immunity to thuricin CD, a narrow-spectrum two-peptide sactibiotic produced byBacillus thuringiensisDPC6431. Heterologous expression of putative thuricin CD immunity determinants allowed us to identify and investigate the relative importance of the individual genes and gene products that contribute to thuricin CD immunity. We established that TrnF and TrnG are the individual components of an ABC transporter system that provides immunity to thuricin CD. We also identified a hitherto overlooked open reading frame located upstream oftrnFpredicted to encode a 79-amino-acid transmembrane protein. We designated this newly discovered genetrnIand established that TrnI alone can provide protection against thuricin CD.