母婴群体乳杆菌组成及优势种副干酪乳酪杆菌的遗传差异性

community composition of Lactobacillus spp. and genetic differences of the dominant species Lacticaseibacillus paracasei in mother-infant pairs

摘要:

肠道中的有益细菌影响人体健康，一般认为早期是通过母乳喂养构建了婴儿肠道菌群。目前对不同人群的母婴群体间有益细菌组成差异及是否具有族群特异性证据很少。【目的】探究不同民族母婴群体间乳杆菌的组成及占优势种——副干酪乳酪杆菌(Lacticaseibacillus paracasei)的垂直传递和遗传差异，为开发个性化的益生菌株提供理论基础。【方法】从我国3个不通婚的民族共39对健康母婴对分离乳杆菌，基于基因外重复回文序列PCR分型技术(repetitive extragenic palindromic PCR, rep-PCR)结合功能基因(groEL基因)序列鉴定菌株，对最常见种L. paracasei的83株菌采用多位点序列分型(multilocus sequence typing, MLST)进行种群遗传差异分析。【结果】三个民族母婴对乳杆菌种类组成和数量存在差异，共分离原乳杆菌属的菌株945株，根据最新修订的分类学隶属于4属1种。汉族母婴以黏膜黏液乳杆菌(Lacticaseibacillus rhamnosus, 20.07%)、L. paracasei (16.54%)和奶酪乳酪杆菌(Lacticaseibacillus casei, 11.90%)为优势种，和田维吾尔族母婴以L. casei (13.55%)、L. paracasei (12.69%)和唾液宿主关联乳杆菌(Ligilactobacillus salivarius, 11.47%)为优势种，海南黎族母婴以口腔黏液乳杆菌(Limosilactobacillus oris, 24.55%)、L. paracasei (15.85%)和加氏乳杆菌(Lactobacillus gasseri, 10.87%)为优势种。83株L. paracasei划分为11个rep-PCR群，基于MLST等位基因谱也分为11群、31个序列型(sequence type, STs)，不同民族菌株的ST存在特异性，同源重组事件很少；来自同一对母子的L. paracasei分离株有相同的STs，同一种族母婴群体的L. paracasei遗传相似性更高。【结论】不同民族母婴群体乳杆菌菌群组成存在明显差异，来源相同的L. paracasei菌株遗传相似性更高，支持菌株水平上的垂直传递和种族间的特异性。

关键词:副干酪乳酪杆菌;多位点序列分型;遗传多样性;指纹图谱

Abstract:

Beneficial bacteria in the gut affect human health, and it is generally believed that the assemblage of healthy gut flora is achieved through vertical transmission of by breastfeeding in early infancy. There is limited evidence for the difference in the composition of beneficial bacteria across different mother-infant cohorts and the presence of population-specific microbial taxa [Objective] To investigate Lactobacillus spp. and the vertical transmission and genetic differences of the dominant species Lacticaseibacillus paracasei among mother-infant cohorts of different ethnic groups, providing a theoretical basis for developing personalized probiotic regimens. [Methods] Lactobacillus strains were isolated from 39 mother-infant pairs of three ethnic groups without mixed marriage in China and identified by repetitive extragenic palindromic PCR (rep-PCR) and groEL sequences. The genetic differences of 83 strains of L. paracasei, a representative species, were analyzed by multilocus sequence typing (MLST). [Results] The species and abundance of Lactobacillus varied among the mother-infant pairs of different ethnic groups. A total of 945 L actobacillus strains were isolated, belonging to 15 species of 4 genera. L. rhamnosus (20.07%), L. paracasei (16.54%), and L. casei (11.90%) were dominant species in the Han ethnic group, while L. casei (13.55%), L. paracasei (12.69%), and Ligilactobacillus salivarius (11.47%) were dominant bacteria in Uighur ethnic group in Hotan. The dominant species in the Li ethnic group in Hainan were Limosilactobacillus oris (24.55%), L. paracasei (15.85%), and Lactobacillus gasseri (10.87%). The 83 strains of L. paracasei were classified into 11 phylogenetic groups by rep-PCR and 31 sequence types (STs) by MLST, demonstrating ethnic specificity. L. paracasei isolates from the same mother-infant pair had the same STs, and isolates from the mother-infant pairs of the same ethnic group had higher genetic similarity. [Conclusion] L actobacil lus species varied in the mother-infant pairs of different ethnic groups, and L. paracase i strains from the same origin displayed higher genetic similarity, which supported vertical transmission at strain level and ethnic specificity.

Key words:Lacticaseibacillus paracasei;multilocus sequence typing;genetic diversity;fingerprint