Mühlig Anna, Kabisch Jan, Pichner Rohtraud, Scherer Siegfried, Müller-Herbst Stefanie
Abteilung Mikrobiologie (ZIEL), Technische Universität München, Weihenstephaner Berg 3, D-85350 Freising, Germany.
Institut für Mikrobiologie und Biotechnologie, MRI, Bundesforschungsinstitut für Ernährung und Lebensmittel, E.-C.-Baumann-Str. 20, D-95326 Kulmbach, Germany.
Food Microbiol. 2014 Sep;42:26-33. doi: 10.1016/j.fm.2014.02.006. Epub 2014 Feb 20.
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.
在生香肠发酵过程中，固化剂亚硝酸钠（NaNO₂）的抗菌作用被认为主要取决于在酸性pH条件下细胞毒性一氧化氮（NO）的释放。鼠伤寒沙门氏菌能够通过黄素血红蛋白HmpA、黄素氧化还原蛋白NorV和周质细胞色素C亚硝酸还原酶NrfA对NO进行解毒。在本研究中，对这些系统在生香肠中对亚硝化应激耐受性的贡献进行了研究。鼠伤寒沙门氏菌14028缺失突变体ΔhmpA、ΔnorV和ΔnrfA的体外生长试验表明，在酸化NaNO₂存在的情况下，ΔhmpA存在生长缺陷。对野生型中hmpA、norV和nrfA基因的转录分析表明，在150 mg/l酸化NaNO₂存在的情况下，hmpA转录水平增加了41倍，而norV和nrfA的转录没有增强。然而，用添加0或150 mg/kg NaNO₂生产的短期成熟可涂抹香肠进行的攻毒试验未能揭示任何突变体与野生型相比的表型。因此，NO解毒系统HmpA、NorV和NrfA中没有一个单独负责鼠伤寒沙门氏菌在生香肠中的亚硝化应激耐受性。目前尚不清楚这些系统是否协同作用，或者是否存在其他尚未描述的机制。
