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首页> 外文会议>International conference of meat science and technology >Physiological state of bacteria growing in meat during cold storage: a molecular approach
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Physiological state of bacteria growing in meat during cold storage: a molecular approach

机译：冷藏过程中肉类生长的生理状态：分子方法

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Bacteria growing on meat are subjected to specific life conditions (nutrient, pH, salt, temperature) which differ drastically from typical laboratory procedures on synthetic media, so physiological and molecular adjustments are expected. This study was conducted to determine the behaviour of bacteria when transferred from a rich-liquid medium to a solid food matrix as it is the case during microbial process validation. Planktonic Escherichia coli cultured in Brain Heart Infusion (BHI) to exponential and stationary growth phases were inoculated onto aseptically prepared ground beef meat and stored at 5°C for 12 days. No growth was observed during storage and time-course expression of sigma factors (encoded by rpoD, E, H, S) and of genes under their transcriptional control was established by RT-PCR. Overall, gene expression profiles were more stable in stationary phase bacteria. After transfer onto refrigerated meat, rpoD mRNA levels increased significantly in exponential phase bacteria (P = 0.0005) but not in stationary phase ones (P = 0.1). The rpoS mRNA levels were not significantly changed whatever the physiological state of the inoculum (P > 0.1) and a decrease of gadA transcription, controlled by σ~s, were only observed after 12 days of cold storage in exponential phase bacteria (P = 0.03). Surprisingly, activation of σ~H was only observed after more than 1 day of storage. Although the sigma factors expression profiles indicate that bacteria quickly adapt, cells do not seem to perceive a real stress after transfer from a rich medium to the cold meat environment.
机译：生长在肉类上的细菌受到特定的寿命条件（营养，pH，盐，温度），其从典型的合成培养基上的实验室程序急剧差异，因此预期生理和分子调整。进行该研究以确定当从浓液体培养基转移到固体食物基质时，在微生物过程验证期间的情况下，均为细菌的行为。在脑心脏输注（BHI）中培养的浮游生物大肠杆菌与指数和固定生长阶段接种到无菌制备的碎牛肉上，并在5℃下储存12天。在RT-PCR确定期间在Sigma因子（RPOD，E，H，S）和基因下，在其转录对照中没有观察到在胰岛素的表达中未观察到生长。总体而言，基因表达谱在固定相细菌中更稳定。在冷冻肉转移到冷藏肉后，逆向阶段细菌的RPOD mRNA水平显着增加（P = 0.0005），但不在固定相阶段（P = 0.1）。无论接种物的生理状态（p> 0.1）和由σ〜s控制的Gada转录的降低，均仅在脑电池阶段细菌的冷储存12天后观察到，RPO mRNA水平没有显着改变（P> 0.1）和GADA转录的降低（P = 0.03 ）。令人惊讶的是，在超过1天的储存后才观察到σ〜h的激活。虽然Sigma因子表达谱表达表达细菌迅速适应，但在从富含培养基转移到冷肉环境之后，细胞似乎似乎并不觉得真正的压力。

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