基于多位点序列分型对新疆伊宁学龄儿童肠道两歧双歧杆菌(Bifidobacterium bifidum)群体遗传差异解析

【背景】两歧双歧杆菌(Bifidobacterium bifidum)是专性代谢人体母乳寡糖(human milk oligosaccharides, HMOs)和宿主肠道黏膜上皮黏蛋白聚糖的肠道共栖益生菌，对生命早期健康和发育至关重要，目前对其不同人群来源的群体遗传报道较少。【目的】探究在有限地域内遗传、饮食相近人群来源的B. bifidum菌株集的遗传结构是否具有族群特异的规律性，为开发个性化的益生菌株提供理论基础。【方法】对来自新疆伊宁两个族群(维吾尔族和哈萨克族)学龄儿童队列的肠道两歧双歧杆菌进行分离和鉴定，共获得115个菌株，对基于细菌基因组重复序列PCR (repetitive sequence-PCR, rep-PCR)方法筛选的53株代表菌株采用多位点序列分型(multilocus sequence typing, MLST)进行群体遗传差异分析。【结果】53株代表菌株共分为37个序列型(sequence type, ST)，具有很高的遗传多样性；其中26株源自维吾尔族儿童的菌株有17个ST，而20个ST来自27株哈萨克族儿童的菌株，两个族群来源的菌株之间检测到较少的同源基因重组事件。goeBURST分析显示，来自同一族群的B. bifidum分离株比来自另一族群的菌株更有可能被归入特定的系统发育分支或克隆复合体(clonal complexes, CC)。【结论】不同族群来源的B. bifidum分离株显示出较高的遗传多样性，群体遗传结构一定程度上呈现出民族族群来源的特异性，需要更大规模的取样证实。这为进一步开展体内外实验并筛选针对区域族群的特色优良益生菌株提供了理论基础。

Genetic differences of intestinal Bifidobacterium bifidum among school-age children in Yining, Xinjiang: a study based on multilocus sequence typing

Background] Bifidobacterium bifidum, an obligate intestinal bacterium that specifically metabolizes human milk oligosaccharides (HMOs) and mucin glycans of host gut epithelium, is essential for early life health and development. However, little is known about the genetic differences of this bacterium among different populations. Objective] To investigate whether the B. bifidum strains from genetically similar populations with similar diets in a limited geographic area have population-specific regularities and to reveal the genetic differences of B. bifidum among different populations. Methods] A total of 115 strains of B. bifidum were isolated and identified from school-age children of Uyghur and Kazak ethnic minorities in Yining, Xinjiang. Further, we performed multilocus sequence typing (MLST) for 53 representative strains screened out by rep-PCR to understand the genetic differences of B. bifidum between different ethnic groups. Results] The 53 strains belonged to 37 sequence types (STs), showing high genetic diversity. Among them, 17 STs were identified for 26 isolates from the children of Uyghur ethnic minority, while 20 STs for 27 isolates from the children of Kazak ethnic minority. Only a few homologous genetic recombination events were detected between strains from both ethnic groups. goeBURST showed that B. bifidum isolates from the same population were more likely to be assigned to a specific phylogenetic clade or clonal complex than the isolates from the other population. Conclusion] B. bifidum isolates from different ethnic groups showed high genetic diversity. The host (ethnic group) specificity of their genetic structure needs to be confirmed by larger sampling. Our findings provide a theoretical basis for further screening of elite probiotic strains tailored to localized population by in vivo and in vitro experiments.