Open AccessDifferential Activation of the tcpPH Promoter by AphB Determines Biotype Specificity of Virulence Gene Expression in Vibrio cholerae
Author(s) -
Gabriela Kovacikova,
Karen Skorupski
Publication year - 2000
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.182.11.3228-3238.2000
Subject(s) - vibrio cholerae , biology , promoter , el tor , gene , virulence , cholera toxin , escherichia coli , lac operon , microbiology and biotechnology , transcription (linguistics) , genetics , gene expression , bacteria , linguistics , philosophy
Vibrio cholerae strains of the classical biotype express the genes encoding cholera toxin (CT) and toxin-coregulated pilus (TCP) under a variety of environmental conditions in vitro, whereas El Tor biotype strains express these genes only under specialized culture conditions. We show here that a single base-pair difference at positions −65 and −66 of the classical and El TortcpPH promoters, respectively, is responsible for the differential regulation of virulence gene expression in these two disease-causing biotypes. Analysis oftcpP-lacZ fusions in bothV. cholerae andEscherichia coli indicated that transcriptional activation of the El TortcpPH promoter by the LysR regulator AphB was significantly reduced relative to that of the classical promoter. Reciprocal exchange of thetcpPH promoter between the two biotypes inV. cholerae showed that the ability to activate the transcription oftcpPH is not dependent on the biotype of the strain per se but on thetcpPH promoter itself. Classical and El TortcpP-lacZ promoter chimeras inE. coli localized the region responsible for the differential activation oftcpPH by AphB to within 75 bp of the transcriptional start site. Individual base-pair changes within this region showed that the presence of either an A or a G at position −65 or −66 conferred the classical or El Tor, respectively, pattern oftcpPH activation by AphB. Reciprocal exchange of these base pairs between biotypes inV. cholerae switched the biotype-specific pattern of expression oftcpPH as well as the production of CT and TCP in response to environmental stimuli.