Diversification of a Fucosyllactose Transporter within the Genus Bifidobacterium
Diversification of a Fucosyllactose Transporter within the Genus Bifidobacterium
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DOI：
10.1128/aem.01437-21
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发表时间：
2022-01-01
影响因子：
4.4
通讯作者：
Katayama, Takane
中科院分区：
文献类型：
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作者：
Ojima, Miriam N.;Asao, Yuya;Katayama, Takane
人乳低聚糖（HMO）是一种天然的生物合成益生元，最近被商业化用于强化配方奶。然而，双歧杆菌的HMO同化表型因物种和菌株而异，这与菌株基因型并不完全相关。我们最近发现，专门的吸收系统，特别是主要HMO（岩藻糖基乳糖[FL]）的内化，与富含双歧杆菌的肠道微生物群落的形成有关。系统发育分析表明，FL转运蛋白已经多样化成两个分支，在双歧杆菌属内有四个簇，但与这种分歧相关的基础功能多样性仍有待研究。在这项研究中，我们研究了两种双歧杆菌的HMO消耗表型，链状双歧杆菌亚种。kashiwanohense和Bifidobacterium pseudocatenulatum，这两种菌都具有属于具有未知特异性的系统发生簇的FL结合蛋白。生长测定、异源基因表达实验和HMO消耗分析表明，来自B的FL转运蛋白类型。小链藻亚种kashiwanohense JCM 15439 T赋予了新的HMO摄取模式，其包括复杂的岩藻糖基化HMO（乳糖-N-岩藻五糖II和乳糖-N-二岩藻六糖I/II）。FL转运蛋白阳性双歧杆菌菌株的进一步基因组景观分析显示，H抗原或刘易斯抗原特异性岩藻糖苷酶基因和FL转运蛋白特异性在很大程度上是一致的。这些结果表明，双歧杆菌已经获得FL转运蛋白沿着相应的基因集，需要利用进口的HMO。我们的研究结果提供了深入了解的物种和菌株依赖的适应策略的双歧杆菌在HMO丰富的environments.IMPORTANCE母乳喂养的婴儿的肠道一般是由健康促进双歧杆菌。母乳中的人乳低聚糖（HMO）选择性地促进特定类群（如双歧杆菌）的生长，从而形成HMO介导的宿主-微生物共生。虽然已经提出了人类和双歧杆菌的共同进化，但双歧杆菌采用的基础适应策略需要进一步研究。在这里，我们分析了分歧的关键岩藻糖基乳糖（FL）HMO转运内双歧杆菌。我们已经表明，FL转运蛋白的溶质结合蛋白的多样化导致岩藻糖基化糖的摄取特异性，从简单的三糖到复杂的六糖。这种转运蛋白和必要的细胞内酶的一致获得允许双歧杆菌以可预测的和菌株依赖的方式消耗不同类型的HMO。这些发现解释了双歧杆菌在竞争性和富含HMO的婴儿肠道环境中的适应和增殖，并使宏基因组数据中转运蛋白的准确特异性注释成为可能。
Human milk oligosaccharides (HMOs), which are natural bifidogenic prebiotics, were recently commercialized to fortify formula milk. However, HMO assimilation phenotypes of bifidobacteria vary by species and strain, which has not been fully linked to strain genotype. We have recently shown that specialized uptake systems, particularly for the internalization of major HMOs (fucosyllactose [FL]), are associated with the formation of a Bifidobacterium-rich gut microbial community. Phylogenetic analysis revealed that FL transporters have diversified into two clades harboring four clusters within the Bifidobacterium genus, but the underpinning functional diversity associated with this divergence remains underexplored. In this study, we examined the HMO consumption phenotypes of two bifidobacterial species, Bifidobacterium catenulatum subsp. kashiwanohense and Bifidobacterium pseudocatenulatum, both of which possess FL-binding proteins that belong to phylogenetic clusters with unknown specificities. Growth assays, heterologous gene expression experiments, and HMO consumption analyses showed that the FL transporter type from B. catenulatum subsp. kashiwanohense JCM 15439T conferred a novel HMO uptake pattern that includes complex fucosylated HMOs (lacto-N-fucopentaose II and lacto-N-difucohexaose I/II). Further genomic landscape analyses of FL transporter-positive bifidobacterial strains revealed that the H-antigen- or Lewis antigen-specific fucosidase gene(s) and FL transporter specificities were largely aligned. These results suggest that bifidobacteria have acquired FL transporters along with the corresponding gene sets necessary to utilize the imported HMOs. Our results provide insight into the species- and strain-dependent adaptation strategies of bifidobacteria in HMO-rich environments.IMPORTANCE The gut of breastfed infants is generally dominated by health-promoting bifidobacteria. Human milk oligosaccharides (HMOs) from breast milk selectively promote the growth of specific taxa such as bifidobacteria, thus forming an HMO-mediated host-microbe symbiosis. While the coevolution of humans and bifidobacteria has been proposed, the underpinning adaptive strategies employed by bifidobacteria require further research. Here, we analyzed the divergence of the critical fucosyllactose (FL) HMO transporter within Bifidobacterium. We have shown that the diversification of the solute-binding proteins of the FL transporter led to uptake specificities of fucosylated sugars ranging from simple trisaccharides to complex hexasaccharides. This transporter and the congruent acquisition of the necessary intracellular enzymes allow bifidobacteria to consume different types of HMOs in a predictable and strain-dependent manner. These findings explain the adaptation and proliferation of bifidobacteria in the competitive and HMO-rich infant gut environment and enable accurate specificity annotation of transporters from metagenomic data.