1. Contribution of the NO-detoxifying enzymes HmpA, NorV and NrfA to nitrosative stress protection of Salmonella Typhimurium in raw sausages.
- Author
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Mühlig A, Kabisch J, Pichner R, Scherer S, and Müller-Herbst S
- Subjects
- Animals, Bacterial Proteins genetics, Cytochromes a1 genetics, Cytochromes c1 genetics, Gene Expression Regulation, Bacterial, Hemeproteins genetics, Nitrate Reductases genetics, Nitrites metabolism, Oxidative Stress drug effects, Salmonella typhimurium genetics, Salmonella typhimurium metabolism, Swine, Transcription Factors genetics, Bacterial Proteins metabolism, Cytochromes a1 metabolism, Cytochromes c1 metabolism, Food Preservatives metabolism, Hemeproteins metabolism, Meat Products microbiology, Nitrate Reductases metabolism, Nitric Oxide metabolism, Salmonella typhimurium enzymology, Transcription Factors metabolism
- 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., (Copyright © 2014 Elsevier Ltd. All rights reserved.)
- Published
- 2014
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