Lab of Beef Processing and Quality Control, College of Food Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, 271018, PR China.
College of Life Science, Shandong Agricultural University, Tai'an, Shandong, 271018, PR China.
Food Microbiol. 2021 May;95:103716. doi: 10.1016/j.fm.2020.103716. Epub 2020 Dec 10.
To investigate the persistence of acid tolerance response (ATR) and the regulatory mechanism during chilled storage, Salmonella ATCC 14028 and the △phoP mutant were acid adapted and then incubated in meat extract at 4 °C for 24 days as simulated beef storage. The bacterial population, D values and expression of PhoP/PhoQ linked genes of both strains were determined at 6-day intervals. Although a mild suppression effect on the D values of adapted Salmonella was found during the long-time storage in meat extract at 4 °C, the D value of adapted strains was significantly higher than non-adapted strains, indicating the persistence of ATR during the whole aging and distribution of beef posing a threat to food safety. The fact that low temperature inhibits the formation of ATR at the early adapted stage emphasizes the importance of keeping a low-temperature environment during slaughter. An interaction between the acidic adaptation and phoP gene on D values was found and the expression levels of adiA, adiY, cadA and cadB genes was significantly reduced in the △phoP mutant, suggesting that PhoP/Q system plays an important role in the ATR by sensing the pH and regulating lysine and arginine decarboxylation directly or indirectly.
为了研究在冷藏储存过程中酸耐受反应（ATR）的持久性和调节机制，将沙门氏菌 ATCC 14028 和 △phoP 突变株进行酸适应，然后在肉浸液中于 4°C 孵育 24 天，模拟牛肉储存。每隔 6 天测定两株菌的细菌数量、D 值和 PhoP/PhoQ 相关基因的表达。尽管在 4°C 的肉浸液中长时间储存对适应后的沙门氏菌的 D 值有轻微的抑制作用，但适应后的菌株的 D 值明显高于未适应的菌株，这表明 ATR 在牛肉的整个老化和分配过程中持续存在，对食品安全构成威胁。低温抑制早期适应阶段 ATR 形成的事实强调了在屠宰过程中保持低温环境的重要性。在 D 值方面发现了酸性适应和 phoP 基因之间的相互作用，并且 △phoP 突变株中 adiA、adiY、cadA 和 cadB 基因的表达水平显著降低，表明 PhoP/Q 系统通过感知 pH 值并直接或间接调节赖氨酸和精氨酸脱羧作用在 ATR 中发挥重要作用。
