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首页> 外文期刊>Applied Microbiology >Genotypic and Phenotypic Analysis of Dairy Lactococcus lactis Biodiversity in Milk: Volatile Organic Compounds as Discriminating Markers
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Genotypic and Phenotypic Analysis of Dairy Lactococcus lactis Biodiversity in Milk: Volatile Organic Compounds as Discriminating Markers

机译：乳中乳酸乳球菌生物多样性的基因型和表型分析：挥发性有机化合物作为判别标记

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The diversity of nine dairy strains of Lactococcus lactis subsp. lactis in fermented milk was investigated by both genotypic and phenotypic analyses. Pulsed-field gel electrophoresis and multilocus sequence typing were used to establish an integrated genotypic classification. This classification was coherent with discrimination of the L. lactis subsp. lactis bv. diacetylactis lineage and reflected clonal complex phylogeny and the uniqueness of the genomes of these strains. To assess phenotypic diversity, 82 variables were selected as important dairy features; they included physiological descriptors and the production of metabolites and volatile organic compounds (VOCs). Principal-component analysis (PCA) demonstrated the phenotypic uniqueness of each of these genetically closely related strains, allowing strain discrimination. A method of variable selection was developed to reduce the time-consuming experimentation. We therefore identified 20 variables, all associated with VOCs, as phenotypic markers allowing discrimination between strain groups. These markers are representative of the three metabolic pathways involved in flavor: lipolysis, proteolysis, and glycolysis. Despite great phenotypic diversity, the strains could be divided into four robust phenotypic clusters based on their metabolic orientations. Inclusion of genotypic diversity in addition to phenotypic characters in the classification led to five clusters rather than four being defined. However, genotypic characters make a smaller contribution than phenotypic variables (no genetic distances selected among the most contributory variables). This work proposes an original method for the phenotypic differentiation of closely related strains in milk and may be the first step toward a predictive classification for the manufacture of starters.
机译：乳酸乳球菌亚种的9个乳品菌株的多样性。通过基因型和表型分析研究了发酵乳中的乳酸菌。脉冲场凝胶电泳和多基因座序列分型被用来建立一个综合的基因型分类。这种分类与乳酸乳球菌亚种的鉴别是一致的。乳酸菌双乙酰actis谱系和反映的克隆复杂系统发育和这些菌株的基因组的唯一性。为了评估表型多样性，选择了82个变量作为重要的乳制品特征。其中包括生理指标以及代谢产物和挥发性有机化合物（VOC）的产生。主成分分析（PCA）显示了这些遗传上密切相关的菌株中每个菌株的表型唯一性，从而可以区分菌株。开发了一种变量选择方法，以减少耗时的实验。因此，我们确定了全部与VOC相关的20个变量，作为可区分菌株组的表型标记。这些标志物代表了涉及风味的三个代谢途径：脂解，蛋白水解和糖酵解。尽管表型多样性很大，但根据其代谢方向，这些菌株仍可分为四个强大的表型簇。在分类中除了表型特征外还包括了基因型多样性，这导致了五个聚类而不是四个聚类。但是，与表型变量相比，基因型特征的贡献较小（在最有贡献的变量中未选择遗传距离）。这项工作提出了一种对牛奶中密切相关的菌株进行表型分化的原始方法，并且可能是朝着制造发酵剂的预测分类迈出的第一步。

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