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首页> 外文期刊>Applied Microbiology >Comparative Phenotypic and Molecular Genetic Profiling of Wild Lactococcus lactis subsp. lactis Strains of the L. lactis subsp. lactis and L. lactis subsp. cremoris Genotypes, Isolated from Starter-Free Cheeses Made of Raw Milk
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Comparative Phenotypic and Molecular Genetic Profiling of Wild Lactococcus lactis subsp. lactis Strains of the L. lactis subsp. lactis and L. lactis subsp. cremoris Genotypes, Isolated from Starter-Free Cheeses Made of Raw Milk

机译：野生乳球菌亚种的比较表型和分子遗传分析。乳酸乳杆菌亚种的菌株。乳酸和乳酸乳亚种。 cremoris基因型，从原奶制成的无酵母奶酪中分离

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Twenty Lactococcus lactis strains with an L. lactis subsp. lactis phenotype isolated from five traditional cheeses made of raw milk with no added starters belonging to the L. lactis subsp. lactis and L. lactis subsp. cremoris genotypes ( lactis and cremoris genotypes, respectively; 10 strains each) were subjected to a series of phenotypic and genetic typing methods, with the aims of determining their phylogenetic relationships and suitability as starters. Pulsed-field gel electrophoresis (PFGE) analysis of intact genomes digested with SalI and SmaI proved that all strains were different except for three isolates of the cremoris genotype, which showed identical PFGE profiles. Multilocus sequence typing (MLST) analysis using internal sequences of seven loci (namely, atpA , rpoA , pheS , pepN , bcaT , pepX , and 16S rRNA gene) revealed considerable intergenotype nucleotide polymorphism, although deduced amino acid changes were scarce. Analysis of the MLST data for the present strains and others from other dairy and nondairy sources showed that all of them clustered into the cremoris or lactis genotype group, by using both independent and combined gene sequences. These two groups of strains also showed distinctive carbohydrate fermentation and enzyme activity profiles, with the strains in the cremoris group showing broader profiles. However, the profiles of resistance/susceptibility to 16 antibiotics were very similar, showing no atypical resistance, except for tetracycline resistance in three identical cremoris genotype isolates. The numbers and concentrations of volatile compounds produced in milk by the strains belonging to these two groups were clearly different, with the cremoris genotype strains producing higher concentrations of more branched-chain, derived compounds. Together, the present results support the idea that the lactis and cremoris genotypes of phenotypic Lactococcus lactis subsp. lactis actually represent true subspecies. Some strains of the two subspecies in this study appear to be good starter candidates.
机译：二十个乳酸乳球菌菌株，带有乳酸乳球菌亚种。从五种由原料奶制成的传统奶酪中分离出的乳酸菌表型，没有添加属于乳酸菌亚种的发酵剂。乳酸和乳酸乳亚种。对cremoris基因型（分别为乳酸菌和creemoris基因型;每个菌株10个）进行了一系列表型和遗传分型方法，目的是确定它们的系统发生关系和作为起始剂的适用性。用SalI和SmaI消化的完整基因组的脉冲场凝胶电泳（PFGE）分析证明，除了3个克雷莫里斯基因型分离株（显示相同的PFGE图谱）外，所有菌株均不同。使用七个基因座（即atpA，rpoA，pheS，pepN，bcaT，pepX和16S rRNA基因）的内部序列进行的多基因座序列分型（MLST）分析显示出可观的基因型核苷酸多态性，尽管缺乏推测的氨基酸变化。对本菌株以及其他奶牛和非奶牛来源的其他菌株的MLST数据进行的分析表明，通过使用独立和组合的基因序列，它们全部聚集成了角膜足动物或乳酸菌基因型组。这两类菌株还表现出独特的碳水化合物发酵和酶活性特征，而cremoris组中的菌株表现出更广泛的特征。然而，对三种抗生素的耐药性/敏感性曲线非常相似，除了在三个相同的克雷莫里斯基因型分离株中对四环素的耐药性外，没有非典型的耐药性。属于这两组的菌株在牛奶中产生的挥发性化合物的数量和浓度明显不同，而鸡腿草属基因型菌株则产生更高浓度的更多支链衍生化合物。总之，目前的结果支持了表型乳酸乳球菌亚种的乳酸和cremoris基因型。乳酸菌实际上代表真正的亚种。在这项研究中，这两个亚种的某些菌株似乎是很好的起始候选者。

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