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首页> 外文期刊>Applied Microbiology >Food Microstructure and Fat Content Affect Growth Morphology, Growth Kinetics, and Preferred Phase for Cell Growth of Listeria monocytogenes in Fish-Based Model Systems
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Food Microstructure and Fat Content Affect Growth Morphology, Growth Kinetics, and Preferred Phase for Cell Growth of Listeria monocytogenes in Fish-Based Model Systems

机译：食物微结构和脂肪含量影响以鱼类为基础的模型系统中单核细胞增生李斯特菌的细胞生长形态，生长动力学和细胞生长的优选阶段

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Food microstructure significantly affects microbial growth dynamics, but knowledge concerning the exact influencing mechanisms at a microscopic scale is limited. The food microstructural influence on Listeria monocytogenes (green fluorescent protein strain) growth at 10°C in fish-based food model systems was investigated by confocal laser scanning microscopy. The model systems had different microstructures, i.e., liquid, xanthan (high-viscosity liquid), aqueous gel, and emulsion and gelled emulsion systems varying in fat content. Bacteria grew as single cells, small aggregates, and microcolonies of different sizes (based on colony radii [size I, 1.5 to 5.0 μm; size II, 5.0 to 10.0 μm; size III, 10.0 to 15.0 μm; and size IV, ≥15 μm]). In the liquid, small aggregates and size I microcolonies were predominantly present, while size II and III microcolonies were predominant in the xanthan and aqueous gel. Cells in the emulsions and gelled emulsions grew in the aqueous phase and on the fat-water interface. A microbial adhesion to solvent assay demonstrated limited bacterial nonpolar solvent affinities, implying that this behavior was probably not caused by cell surface hydrophobicity. In systems containing 1 and 5% fat, the largest cell volume was mainly represented by size I and II microcolonies, while at 10 and 20% fat a few size IV microcolonies comprised nearly the total cell volume. Microscopic results (concerning, e.g., growth morphology, microcolony size, intercolony distances, and the preferred phase for growth) were related to previously obtained macroscopic growth dynamics in the model systems for an L. monocytogenes strain cocktail, leading to more substantiated explanations for the influence of food microstructural aspects on lag phase duration and growth rate.IMPORTANCEListeria monocytogenes is one of the most hazardous foodborne pathogens due to the high fatality rate of the disease (i.e., listeriosis). In this study, the growth behavior of L. monocytogenes was investigated at a microscopic scale in food model systems that mimic processed fish products (e.g., fish paté and fish soup), and the results were related to macroscopic growth parameters. Many studies have previously focused on the food microstructural influence on microbial growth. The novelty of this work lies in (i) the microscopic investigation of products with a complex composition and/or structure using confocal laser scanning microscopy and (ii) the direct link to the macroscopic level. Growth behavior (i.e., concerning bacterial growth morphology and preferred phase for growth) was more complex than assumed in common macroscopic studies. Consequently, the effectiveness of industrial antimicrobial food preservation technologies (e.g., thermal processing) might be overestimated for certain products, which may have critical food safety implications.
机译：食品的微观结构会显着影响微生物的生长动力学，但是有关微观尺度上确切影响机制的知识却有限。通过共聚焦激光扫描显微镜研究了在鱼类为基础的食物模型系统中，食物微结构对单核细胞增生李斯特菌（绿色荧光蛋白菌株）在10°C下的生长的影响。模型系统具有不同的微观结构，即液体，黄原胶（高粘度液体），水凝胶以及脂肪含量不同的乳液和胶凝乳液体系。细菌以单细胞，小聚集体和不同大小的微菌落生长（基于菌落半径[I大小，1.5至5.0μm; II大小，5.0至10.0μm; III大小，10.0至15.0μm; IV大小，≥15 [μm]）。在液体中，主要存在小聚集体和大小为I的微菌落，而在黄原胶和水性凝胶中主要存在大小为II和III的微菌落。乳液和胶凝乳液中的细胞在水相和脂肪-水界面上生长。微生物对溶剂的粘附测定表明细菌非极性溶剂的亲和力有限，这表明这种行为可能不是由细胞表面疏水性引起的。在含有1％和5％脂肪的系统中，最大的细胞体积主要由大小I和II的微菌落代表，而在10％和20％的脂肪中，少量大小IV的微生物菌落几乎占据了整个细胞的体积。微观结果（例如，关于生长形态，微菌落大小，菌落间距离和优选的生长阶段）与单核细胞增生李斯特氏菌菌株混合物模型系统中先前获得的宏观生长动力学有关，从而导致对这些结果的更充分的解释。食品微结构方面对迟滞期持续时间和生长速率的影响。重要提示单核细胞增生李斯特菌是致病性最高的食源性致病菌之一，因为该病的致死率很高（即李斯特菌病）。在这项研究中，在模拟加工鱼制品（例如鱼片和鱼汤）的食品模型系统中，以微观尺度研究了单核细胞增生李斯特氏菌的生长行为，其结果与宏观生长参数有关。以前，许多研究都集中在食物微结构对微生物生长的影响上。这项工作的新颖性在于（i）使用共聚焦激光扫描显微镜对具有复杂成分和/或结构的产品进行微观研究，以及（ii）与宏观水平直接相关。生长行为（即，涉及细菌生长形态和生长的优选阶段）比普通的宏观研究所假设的更为复杂。因此，对于某些产品，可能会高估工业抗菌食品保存技术（例如热处理）的有效性，这可能会对食品安全产生重大影响。

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