Abstract
A concern regarding the use of bacteriocins, as for example the lantibiotic nisin, for biopreservation of certain food products is the possibility of resistance development and potential cross-resistance
to antibiotics in the target organism. The genetic basis for nisin resistance development is as yet unknown. We analyzed changes in gene expression following nisin resistance development in
Listeria
monocytogenes
412 by restriction fragment differential display. The mutant had increased expression of a protein with strong homology to the glycosyltransferase domain of high-molecular-weight penicillin-binding
proteins (PBPs), a histidine protein kinase, a protein of unknown function, and ClpB (putative functions from homology). The three former proteins had increased expression in a total of six out of 10 independent
mutants originating from five different wild-type strains, indicating a prevalent nisin resistance mechanism under the employed isolation conditions. Increased expression of the putative PBP may affect
the cell wall composition and thereby alter the sensitivity to cell wall-targeting compounds. The mutants had an isolate-specific increase in sensitivity to different β-lactams and a slight decrease
in sensitivity to another lantibiotic, mersacidin. A model incorporating these observations is proposed based on current knowledge of nisin's mode of action.