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Applied and Environmental Microbiology, July 2005, p. 3565-3574, Vol. 71, No. 7
0099-2240/05/$08.00+0 doi:10.1128/AEM.71.7.3565-3574.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Norwegian University of Life Sciences, Department of Chemistry, Biotechnology and Food Science, Chr. M. Falsensvei 1, P.O. Box 5003, N-1432 Ås, Norway,1 Institute of Human Genetics, Schwabachanlage 10, D-91054 Erlangen, Germany,2 Federal Research Centre for Nutrition and Food, Institute for Microbiology and Toxicology, E.-C.-Baumann-Strasse 20, D-95326 Kulmbach, Germany,3 Matforsk AS, Norwegian Food Research Institute, Osloveien 1, N-1430 Ås, Norway4
Received 4 October 2004/ Accepted 17 January 2005
Previous studies of genes involved in the production of sakacin P by Lactobacillus sakei Lb674 revealed the presence of an inducible promoter downstream of the known spp gene clusters. We show here that this promoter drives the expression of an operon consisting of a bacteriocin gene (sppQ), a cognate immunity gene (spiQ), another gene with an unknown function (orf4), and a pseudoimmunity gene containing a frameshift mutation (orf5). The leader peptide of the new one-peptide bacteriocin sakacin Q contains consensus elements that are typical for so-called "double-glycine" leader peptides. The mature bacteriocin shows weak similarity to the BrcA peptide of the two-peptide bacteriocin brochocin C. Sakacin Q has an antimicrobial spectrum that differs from that of sakacin P, thus expanding the antimicrobial properties of the producer strain. The genes encoding sakacin Q and its cognate immunity protein showed strong translational coupling, which was investigated in detail by analyzing the properties of a series of ß-glucuronidase fusions. Our results provide experimental evidence that production of the bacteriocin and production of the cognate immunity protein are tightly coregulated at the translational level.
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