Differential Regulation of the Surface-Exposed and Secreted SslE Lipoprotein in Extraintestinal Pathogenic Escherichia coli.
Extra-intestinal pathogenic Escherichia coli (ExPEC) are responsible for diverse infections including meningitis, sepsis and urinary tract infections. The alarming rise in anti-microbial resistance amongst ExPEC complicates treatment and has highlighted the need for alternative preventive measures. SslE is a lipoprotein secreted by a dedicated type II secretion system in E. coli that was first identified as a potential vaccine candidate using reverse genetics. Although the function and protective efficacy of SslE has been studied, the molecular mechanisms that regulate SslE expression remain to be fully elucidated. Here, we show that while the expression of SslE can be detected in E. coli culture supernatants, different strains express and secrete different amounts of SslE when grown under the same conditions. While the histone-like transcriptional regulator H-NS strongly represses sslE at ambient temperatures, the variation in SslE expression at human physiological temperature suggested a more complex mode of regulation. Using a genetic screen to identify novel regulators of sslE in the high SslE-expressing strain UTI89, we defined a new role for the nucleoid-associated regulator Fis and the ribosome-binding GTPase TypA as positive regulators of sslE transcription. We also showed that Fis-mediated enhancement of sslE transcription is dependent on a putative Fis-binding sequence located upstream of the -35 sequence in the core promoter element, and provide evidence to suggest that Fis may work in complex with H-NS to control SslE expression. Overall, this study has defined a new mechanism for sslE regulation and increases our understanding of this broadly conserved E. coli vaccine antigen.
Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, QLD 4072, Brisbane, Australia.
Lendl
L
Tan
Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, QLD 4072, Brisbane, Australia.
Danilo G
DG
Moriel
Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology, QLD 4059, Brisbane, Australia.
Makrina
M
Totsika
Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, QLD 4072, Brisbane, Australia.
Scott A
SA
Beatson
Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, QLD 4072, Brisbane, Australia.
Mark A
http://orcid.org/0000-0003-4863-9260
MA
Schembri
D001483:Base Sequence; D001665:Binding Sites; D004927:Escherichia coli Infections; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D000072282:Extraintestinal Pathogenic Escherichia coli / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D035021:Factor For Inversion Stimulation Protein / Q000235:genetics* / Q000378:metabolism; D036781:Fimbriae Proteins / Q000235:genetics* / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D009154:Mutation; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D014158:Transcription, Genetic; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism
D029968:Escherichia coli Proteins; D035021:Factor For Inversion Stimulation Protein; C529458:FimG protein, E coli; C501034:Fis protein, E coli; D010750:Phosphoproteins; C583861:SslE protein, E coli; D037521:Virulence Factors; D036781:Fimbriae Proteins; D020558:GTP Phosphohydrolases; C408370:typA protein, E coli