title: Contribution of the NO-detoxifying enzymes HmpA, NorV and NrfA to nitrosative stress protection of Salmonella Typhimurium in raw sausages.
abstract: The antimicrobial action of the curing agent sodium nitrite (NaNO2) in raw sausage fermentation is thought to mainly depend on the release of cytotoxic nitric oxide (NO) at acidic pH. Salmonella Typhimurium is capable of detoxifying NO via the flavohemoglobin HmpA, the flavorubredoxin NorV and the periplasmic cytochrome C nitrite reductase NrfA. In this study, the contribution of these systems to nitrosative stress tolerance in raw sausages was investigated. In vitro growth assays of the S. Typhimurium 14028 deletion mutants ΔhmpA, ΔnorV and ΔnrfA revealed a growth defect of ΔhmpA in the presence of acidified NaNO2. Transcriptional analysis of the genes hmpA, norV and nrfA in the wild-type showed a 41-fold increase in hmpA transcript levels in the presence of 150 mg/l acidified NaNO2, whereas transcription of norV and nrfA was not enhanced. However, challenge assays performed with short-ripened spreadable sausages produced with 0 or 150 mg/kg NaNO2 failed to reveal a phenotype for any of the mutants compared to the wild-type. Hence, none of the NO detoxification systems HmpA, NorV and NrfA is solely responsible for nitrosative stress tolerance of S. Typhimurium in raw sausages. Whether these systems act cooperatively, or if there are other yet undescribed mechanisms involved is currently unknown.
authors.affiliation: Abteilung Mikrobiologie (ZIEL), Technische Universität München, Weihenstephaner Berg 3, D-85350 Freising, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Mühlig
authors.affiliation: Institut für Mikrobiologie und Biotechnologie, MRI, Bundesforschungsinstitut für Ernährung und Lebensmittel, E.-C.-Baumann-Str. 20, D-95326 Kulmbach, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Kabisch
authors.affiliation: Institut für Mikrobiologie und Biotechnologie, MRI, Bundesforschungsinstitut für Ernährung und Lebensmittel, E.-C.-Baumann-Str. 20, D-95326 Kulmbach, Germany.
authors.forename: Rohtraud
authors.initials: R
authors.lastname: Pichner
authors.affiliation: Abteilung Mikrobiologie (ZIEL), Technische Universität München, Weihenstephaner Berg 3, D-85350 Freising, Germany; Lehrstuhl für Mikrobielle Ökologie, Technische Universität München, Weihenstephaner Berg 3, D-85350 Freising, Germany.
authors.forename: Siegfried
authors.initials: S
authors.lastname: Scherer
authors.affiliation: Abteilung Mikrobiologie (ZIEL), Technische Universität München, Weihenstephaner Berg 3, D-85350 Freising, Germany; Lehrstuhl für Mikrobielle Ökologie, Technische Universität München, Weihenstephaner Berg 3, D-85350 Freising, Germany. Electronic address: stefanie.mueller@wzw.tum.de.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Müller-Herbst
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D045263:Cytochromes a1 / Q000235:genetics / Q000378:metabolism*; D003575:Cytochromes c1 / Q000235:genetics / Q000378:metabolism*; D005520:Food Preservatives / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006420:Hemeproteins / Q000235:genetics / Q000378:metabolism*; D008461:Meat Products / Q000382:microbiology*; D009565:Nitrate Reductases / Q000235:genetics / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D012486:Salmonella typhimurium / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D013552:Swine; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D005520:Food Preservatives; D006420:Hemeproteins; D009573:Nitrites; D014157:Transcription Factors; C086193:flavohemoprotein, Bacteria; D009569:Nitric Oxide; D045263:Cytochromes a1; D003575:Cytochromes c1; D009565:Nitrate Reductases; C054690:nitrate reductase (cytochrome)
keywords: Flavohemoglobin HmpA; NO detoxification; Raw sausage; Salmonella Typhimurium; Sodium nitrite