Differential Regulation of the Surface-Exposed and Secreted SslE Lipoprotein in Extraintestinal Pathogenic Escherichia coli

• Published in: PloS one 2016-09, Vol.11 (9), p.e0162391-e0162391
• Main Authors: Tan, Lendl, Moriel, Danilo G, Totsika, Makrina, Beatson, Scott A, Schembri, Mark A
• Format: Article
• Language: English
• Subjects: Ambient temperature; Antibiotics; Antigens; Antiinfectives and antibacterials; Bacteria; Base Sequence; Binding; Binding Sites; Biology and Life Sciences; Deoxyribonucleic acid; Diagnosis; DNA; E coli; Escherichia coli; Escherichia coli Infections; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Extraintestinal Pathogenic Escherichia coli - genetics; Extraintestinal Pathogenic Escherichia coli - isolation & purification; Extraintestinal Pathogenic Escherichia coli - metabolism; Factor For Inversion Stimulation Protein - genetics; Factor For Inversion Stimulation Protein - metabolism; Fimbriae Proteins - genetics; Fimbriae Proteins - metabolism; Gene expression; Gene Expression Regulation, Bacterial; Genetic engineering; Genetic screening; Genetics; Genomics; GTP Phosphohydrolases - genetics; GTP Phosphohydrolases - metabolism; Guanosine triphosphatases; Health aspects; Humans; Immunization; Infections; Infectious diseases; Intestine; Kinases; Lipoprotein A; Medicine and Health Sciences; Meningitis; Microorganisms; Molecular modelling; Mutation; Phosphoproteins - genetics; Phosphoproteins - metabolism; Physiology; Plasmids; Promoter Regions, Genetic; Protein Binding; Proteins; Regulators; Research and analysis methods; Risk factors; Salmonella; Secretion; Sepsis; Transcription; Transcription, Genetic; Urinary tract; Urinary tract infections; Vaccines; Virulence Factors - genetics; Virulence Factors - metabolism
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0162391

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.