Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Dept. of Agriculture, 600 East Mermaid Lane, Wyndmoor, PA 19038, U.S.A.
J Food Sci. 2013 Sep;78(9):M1392-8. doi: 10.1111/1750-3841.12181. Epub 2013 Aug 2.
Listeria monocytogenes is a foodborne pathogen that is difficult to eliminate due to its ability to survive under different stress conditions such as low pH and high salt. To better control this pathogen in food, it is important to understand its survival mechanisms under these stress conditions. LMOf2365_0442, 0443, and 0444 encode for phosphotransferase transport system (PTS) permease (fructose-specific IIABC components) that is responsible for sugar transport. LMOf2365_0445 encodes for glycosyl hydrolase. These genes were induced by high pressure and inhibited under salt treatments; therefore, we hypothesized that genes encoding these PTS proteins may be involved in general stress responses. To study the function of these genes, deletion mutants of the PTS genes (LMOf2365_0442, LMOf2365_0443, and LMOf2365_0444) and the downstream gene LMOf2365_0445 were created in L. monocytogenes strain F2365. These deletion mutants were tested under different stress conditions. The growth of ∆LMOf2365_0445 was increased under nisin (125 μg/mL) treatments compared to the wild-type (P < 0.01). The growth of ∆LMOf2365_0442 in salt (brain-heart infusion medium with 5% NaCl) was significantly increased (P < 0.01), and ∆LMOf2365_0442 showed increased growth under acidic conditions (pH 5.0) compared to the wild-type (P < 0.01). The results from phenotypic arrays demonstrated that some of these mutants showed slightly slower growth under different carbon sources and basic conditions. The results indicate that deletion mutants ∆LMOf2365_0442 and ∆LMOf2365_0445 were more resistant to multiple stress conditions compared to the wild-type, suggesting that they may contribute to the general stress response in L. monocytogenes. An understanding of the growth of these mutants under multiple stress conditions may assist in the development of intervention strategies to control L. monocytogenes in food.
单增李斯特菌是一种食源性病原体，由于其能够在低 pH 值和高盐等不同应激条件下生存，因此很难消除。为了更好地控制食品中的这种病原体，了解其在这些应激条件下的生存机制非常重要。LMOf2365_0442、0443 和 0444 编码磷酸转移酶运输系统（PTS）通透酶（果糖特异性 IIABC 成分），负责糖的运输。LMOf2365_0445 编码糖苷水解酶。这些基因受高压诱导，盐处理时被抑制；因此，我们假设编码这些 PTS 蛋白的基因可能参与一般应激反应。为了研究这些基因的功能，在李斯特菌 F2365 株中构建了 PTS 基因（LMOf2365_0442、LMOf2365_0443 和 LMOf2365_0444）和下游基因 LMOf2365_0445 的缺失突变体。在不同的应激条件下测试了这些缺失突变体。与野生型相比，∆LMOf2365_0445 在乳链菌肽（125 μg/mL）处理下的生长增加（P < 0.01）。∆LMOf2365_0442 在盐（含 5%NaCl 的脑心浸液培养基）中的生长显著增加（P < 0.01），与野生型相比，∆LMOf2365_0442 在酸性条件（pH 5.0）下的生长增加（P < 0.01）。表型数组的结果表明，这些突变体中的一些在不同的碳源和碱性条件下生长稍慢。结果表明，与野生型相比，缺失突变体 ∆LMOf2365_0442 和 ∆LMOf2365_0445 对多种应激条件更具抗性，表明它们可能有助于李斯特菌的一般应激反应。了解这些突变体在多种应激条件下的生长情况，可能有助于制定控制食品中单增李斯特菌的干预策略。
