College of Food Science and Engineering/Collaborative Innovation Center for Modern Grain Circulation and Safety/Key Laboratory of Grains and Oils Quality Control and Processing, Nanjing University of Finance and Economics, Nanjing 210023, China.
Institute of Veterinary Immunology & Engineering, National Research Center of Engineering and Technology for Veterinary Biologicals, Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base, Ministry of Science and Technology, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China.
Food Res Int. 2022 Jul;157:111400. doi: 10.1016/j.foodres.2022.111400. Epub 2022 May 30.
Pseudomonas fragi is by far one of the most threatening species in the spoilage of chilled meat that is stored under aerobic conditions. The membrane protein AprD is a well-established regulator controlling protease secretion in Pseudomonas spp. However, its exact roles in modulating metabolic pathways and spoilage potential of P. fragi at the molecular level remain undefined. Here, an in-frame deletion mutation of aprD was used to explore the impacts on their biofilm structure, matrix secretion, and cell metabolism. The results showed that ΔaprD formed relatively disorganized loose aggregation in biofilm, resulting in a thinner structure and more dead cells. Meanwhile, marked changes in the content of extracellular carbohydrates and proteins were observed. Furthermore, intracellular metabolomic profiling revealed the involvement of aprD in several cellular metabolic pathways, mostly including the carbohydrate pathway, amino acid pathway, and nucleotide pathway, while the characterization of extracellular metabolism clarified the variations in the spoilage-related metabolites (e.g., creatine, IMP, spermine, fatty acids, amino acids, and oligopeptides) could be highly correlated with aprD deletion. In this finding, we indicated that aprD could be responsible for cell reproduction and in situ spoilage potential of P. fragi NMC25 during chilled storage by controlling related metabolism and nutrients utilization. Thus, our results will contribute to an improved understanding of the regulatory mechanism of aprD gene in meat spoilage contaminated with P. fragi, which can be valuable to ensure the quality and safety of meat.
脆弱假单胞菌是迄今为止在有氧条件下储存的冷却肉腐败中最具威胁的物种之一。膜蛋白 AprD 是一种成熟的调控因子，可控制假单胞菌属中蛋白酶的分泌。然而，其在分子水平上调节代谢途径和脆弱假单胞菌腐败潜力的确切作用仍未确定。在这里，使用 aprD 的框内缺失突变来探索其对生物膜结构、基质分泌和细胞代谢的影响。结果表明，Δ aprD 在生物膜中形成相对无序的松散聚集，导致结构更薄和更多的死细胞。同时，观察到细胞外碳水化合物和蛋白质含量的明显变化。此外，细胞内代谢组学分析表明 aprD 参与了几个细胞代谢途径，主要包括碳水化合物途径、氨基酸途径和核苷酸途径，而细胞外代谢的特征阐明了与腐败相关的代谢物（例如肌酸、IMP、亚精胺、脂肪酸、氨基酸和寡肽）的变化与 aprD 缺失高度相关。在这一发现中，我们表明 aprD 可以通过控制相关代谢和营养物质利用来负责冷却储存期间 P. fragi NMC25 的细胞繁殖和原位腐败潜力。因此，我们的研究结果将有助于更好地理解 aprD 基因在受 P. fragi 污染的肉类腐败中的调控机制，这对于确保肉类的质量和安全具有重要意义。
