Open AccessIdentification, Characterization, and Expression of a Second, Bicistronic, Operon Involved in the Production of Lactocin S in Lactobacillus sakei L45
Author(s) -
Morten Skaugen,
Elizabeth L. Andersen,
Vigdis H. Christie,
Ingolf F. Nes
Publication year - 2002
Publication title -
applied and environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.552
H-Index - 324
eISSN - 1070-6291
pISSN - 0099-2240
DOI - 10.1128/aem.68.2.720-727.2002
Subject(s) - operon , open reading frame , biology , regulon , lactobacillus sakei , genetics , gene , mutant , promoter , transcription (linguistics) , gal operon , lac operon , gene expression , bacteria , lactobacillus , peptide sequence , linguistics , philosophy
Through the analysis of spontaneous insertion mutants of Lactobacillus sakei L45, a second operon involved in lactocin S production was identified and characterized. The new, bicistronic unit, termed lasXY, is situated immediately upstream of the previously characterized nine-open reading frame (ORF) lactocin S operon (lasA-W) and is transcribed in the opposite direction. The proximal of the two newly identified genes, lasX, specifies a 285-residue protein that is similar to a group of proteins with reported gene regulation functions in gram-positive bacteria. It was demonstrated that the lasX mutants have a strongly reduced level of lasA and lasA-W mRNA, thus indicating the likely cause of the Bac(-) phenotype of these mutants. The second ORF in the operon, lasY, specifies a 300-residue ABC transporter homolog, the function of which is currently obscure. Transcription initiation mapping of the lasXY operon demonstrates that the two lactocin S promoters overlap such that both transcripts initiate within the -35 region of the oppositely oriented promoter. This organization of promoters is unique among this group of regulons and may constitute a modulatory site in the proposed LasX-dependent expression of lasA and downstream genes.