The rpoS-dependent starvation-stress response locus stiA encodes a nitrate reductase (narZYWV) required for carbon-starvation-inducible thermotolerance and acid tolerance in Salmonella typhimurium

• Published in: Microbiology (Society for General Microbiology) 1999-11, Vol.145 (11), p.3035-3045
• Main Authors: Spector, Michael P, Garcia del Portillo, Francisco, Bearson, Shawn M. D, Mahmud, Atif, Magut, Maureen, Finlay, B. Brett, Dougan, Gordon, Foster, John W, Pallen, Mark J
• Format: Article
• Language: English
• Subjects: Action of physical and chemical agents on bacteria; Amino Acid Sequence; Animals; Artificial Gene Fusion; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Biological and medical sciences; Cell Line; Culture Media - chemistry; DNA Transposable Elements; Escherichia coli Proteins; Fundamental and applied biological sciences. Psychology; Genes, Regulator; Genetics; Hydrogen-Ion Concentration; Iron-Sulfur Proteins - genetics; Lac Operon - physiology; Mice; Mice, Inbred BALB C; Microbiology; Mutation; Nitrate Reductase; Nitrate Reductases - genetics; Nitrate Reductases - metabolism; rpoS protein; Salmonella typhimurium; Salmonella typhimurium - pathogenicity; Salmonella typhimurium - physiology; Sigma Factor; stiA gene; Temperature; Virulence
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/00221287-145-11-3035

Department of Biomedical Sciences 1 and Department of Microbiology and Immunology 2 , University of South Alabama, Mobile, AL 36688, USA Biotechnology Laboratory and Departments of Biochemistry and Microbiology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3 3 Department of Biochemistry, Imperial College of Science, Technology and Medicine, London SW7 2AY, UK 4 Author for correspondence: Michael P. Spector. Tel: [phone]. Fax: [phone]. e-mail: mspector{at}usamail.usouthal.edu The starvation-stress response (SSR) of Salmonella typhimurium includes gene products necessary for starvation avoidance, starvation survival and virulence for this bacterium. Numerous genetic loci induced during carbon-source starvation and required for the long-term-starvation survival of this bacterium have been identified. The SSR not only protects the cell against the adverse effects of long-term starvation but also provides cross-resistance to other environmental stresses, e.g. thermal challenge (55 °C) or acid-pH challenge (pH 2·8). One carbon-starvation-inducible lac fusion, designated stiA was previously reported to be a S -dependent SSR locus that is phosphate-starvation, nitrogen-starvation and H 2 O 2 inducible, positively regulated by (p)ppGpp in a relA -dependent manner, and negatively regulated by cAMP:cAMP receptor protein complex and OxyR. We have discovered through sequence analysis and subsequent biochemical analysis that the stiA :: lac fusion, and a similarly regulated lac fusion designated sti-99 , lie at separate sites within the first gene ( narZ ) of an operon encoding a cryptic nitrate reductase ( narZYWV ) of unknown physiological function. In this study, it was demonstrated that narZ was negatively regulated by the global regulator Fnr during anaerobiosis. Interestingly, narZ(YWV ) was required for carbon-starvation-inducible thermotolerance and acid tolerance. In addition, narZ expression was induced ~20-fold intracellularly in Madin-Darby canine kidney epithelial cells and ~16-fold in intracellular salts medium, which is believed to mimic the intracellular milieu. Also, a narZ1 knock-out mutation increased the LD 50 ~10-fold for S. typhimurium SL1344 delivered orally in the mouse virulence model. Thus, the previously believed cryptic and constitutive narZYWV operon is in fact highly regulated by a complex network of environmental-stress signals and global regulatory functions, indicating a central role in the ph