title: Transmission of an oxygen availability signal at the Salmonella enterica serovar Typhimurium fis promoter.
abstract: The nucleoid-associated protein FIS is a global regulator of gene expression and chromosome structure in Escherichia coli and Salmonella enterica. Despite the importance of FIS for infection and intracellular invasion, very little is known about the regulation of S. enterica fis expression. Under standard laboratory growth conditions, fis is highly expressed during rapid growth but is then silenced as growth slows. However, if cells are cultured in non-aerated conditions, fis expression is sustained during stationary phase. This led us to test whether the redox-sensing transcription factors ArcA and FNR regulate S. enterica fis. Deletion of FNR had no detectable effect, whereas deletion of ArcA had the unexpected effect of further elevating fis expression in stationary phase. ArcA required RpoS for induction of fis expression, suggesting that ArcA indirectly affects fis expression. Other putative regulators were found to play diverse roles: FIS acted directly as an auto-repressor (as expected), whereas CRP had little direct effect on fis expression. Deleting regions of the fis promoter led to the discovery of a novel anaerobically-induced transcription start site (Pfis-2) upstream of the primary transcription start site (Pfis-1). Promoter truncation also revealed that the shortest functional fis promoter was incapable of sustained expression. Moreover, fis expression was observed to correlate directly with DNA supercoiling in non-aerated conditions. Thus, the full-length S. enterica fis promoter region may act as a topological switch that is sensitive to stress-induced duplex destabilisation and up-regulates expression in non-aerated conditions.
authors.affiliation: Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland ; Department of Biology, University of Regina, Regina, SK, Canada.
authors.forename: Andrew D S
authors.initials: AD
authors.lastname: Cameron
authors.affiliation: Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland.
authors.forename: Carsten
authors.initials: C
authors.lastname: Kröger
authors.affiliation: Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland.
authors.forename: Heather J
authors.initials: HJ
authors.lastname: Quinn
authors.affiliation: Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland.
authors.forename: Isobel K
authors.initials: IK
authors.lastname: Scally
authors.affiliation: Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland.
authors.forename: Anne J
authors.initials: AJ
authors.lastname: Daly
authors.affiliation: Department of Biology, University of Regina, Regina, SK, Canada.
authors.forename: Stefani C
authors.initials: SC
authors.lastname: Kary
authors.affiliation: Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland.
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Dorman
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001483:Base Sequence; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics; D035021:Factor For Inversion Stimulation Protein / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D023061:Gene Order; D008969:Molecular Sequence Data; D009154:Mutation; D010100:Oxygen / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000378:metabolism; D012486:Salmonella typhimurium / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; D035021:Factor For Inversion Stimulation Protein; C501034:Fis protein, E coli; D012097:Repressor Proteins; D014157:Transcription Factors; D010100:Oxygen