Abstract—

The ability to ferment lactose is a characteristic peculiarity of dairy Kluyveromyces lactis yeasts; the vast majority of other yeast species are not able to assimilate this disaccharide. Molecular polymorphism of LAC4 genes encoding β-galactosidase controlling lactose fermentation is not well studied, and the published data concern only a single strain (K. lactis var. lactis NRRL Y-1140) isolated from cream in the United States. We studied β-galactosidase genes in lactose-fermenting K. lactis strains isolated from dairy products and natural sources in different regions of the world using molecular karyotyping, Southern hybridization, and sequencing. It was established that the ability to ferment lactose in K. lactis var. lactis dairy yeasts is controlled by at least three polymeric LAC loci with different chromosomal localization: LAC1 (chromosome III), LAC2 (II), and LAC3 (IV). Most of the strains we studied had the LAC2 locus. A comparative analysis of β-galactosidases of the Kluyveromyces genus yeasts and these enzymes from other yeasts was conducted for the first time. Phylogenetic analysis detected significant differences between the LAC4 proteins of yeasts of the Kluyveromyces genus (K. lactis, K. marxianus, К. aestuarii, K. nonfermentans, K. wickerhamii), Scheffersomyces stipitis, Sugiyamaella lignohabitans, and Debaryomyces hansenii. A correlation between β-galactosidase sequences and ecological origin (dairy products and natural sources) of Kluyveromyces strains was found. The group of dairy strains is heterogeneous and includes K. lactis var. lactis and K. marxianus yeasts (99.80–100% similarity), which indicates a common origin of their LAC4 genes. Phylogenetic analysis of β-galactosidases indicates a close genetic relationship of dairy and hospital strains of K. lactis var. lactis and K. marxianus. Clinical isolates are able to ferment lactose and appear to originate from the dairy yeasts.

中文翻译：

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克鲁维酵母酵母乳和天然菌株中β-半乳糖苷酶LAC4基因的分子多态性

摘要-

发酵乳糖的能力是乳克鲁维 酵母乳酸菌的特征。绝大多数其他酵母菌种无法吸收这种二糖。的分子多态性LAC4编码β半乳糖苷酶控制乳糖发酵基因没有很好地研究，并且已发布的数据仅涉及一个单一菌株（乳酸克鲁维酵母变种球菌NRRL Y-1140）从在美国奶油分离。我们研究了乳糖发酵乳酸克鲁维酵母中的β-半乳糖苷酶基因使用分子核型分析，Southern杂交和测序从世界各地不同的乳制品和天然资源中分离出的菌株。已经确定了在乳酸克鲁维酵母中发酵乳糖的能力。乳酸乳酵母由至少三个具有不同染色体定位的聚合LAC基因座控制：LAC1（染色体III），LAC2（II）和LAC3（IV）。我们研究的大多数菌株都具有LAC2基因座。克鲁维酵母β-半乳糖苷酶的比较分析属酵母和其他酵母中的这些酶是首次进行的。系统发育分析检测到的酵母的LAC4蛋白质之间显著差异克鲁维酵母属（乳酸克鲁维酵母，马克斯克鲁维酵母，К.aestuarii，K. nonfermentans，K. wickerhamii），Scheffersomyces树干毕赤酵母，Sugiyamaella lignohabitans，和汉逊德巴利酵母。发现了克鲁维酵母菌株的β-半乳糖苷酶序列与生态起源（乳制品和自然来源）之间的相关性。乳品菌株组是异种的，包括乳酸克鲁维酵母变种 球菌和马克斯克鲁维酵母（99.80-100％的相似性），这表明它们的共同起源LAC4基因。对β-半乳糖苷酶的系统进化分析表明，乳业和乳酸克鲁维酵母菌株与医院菌株之间存在密切的遗传关系。乳酸和K. marxianus。临床分离株能够发酵乳糖，并且似乎起源于乳品酵母。