Microbial Metabolic Capacity for Intestinal Folate Production and Modulation of Host Folate Receptors
Microbial Metabolic Capacity for Intestinal Folate Production and Modulation of Host Folate Receptors
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DOI：
10.3389/fmicb.2019.02305
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发表时间：
2019-10-09
影响因子：
5.2
通讯作者：
Versalovic, James
中科院分区：
文献类型：
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作者：
Engevik, Melinda A.;Morra, Christina N.;Versalovic, James
包括复合维生素B在内的微生物代谢产物有助于人类健康的各个方面。叶酸或维生素B-9是指包括蝶呤、对氨基苯甲酸（pABA）和谷氨酸亚基的大类生物分子。叶酸是DNA合成和表观遗传调控所必需的。除了膳食营养素，肠道微生物群已被认为是B复合维生素的来源，包括叶酸。本研究评估了人类微生物组计划中鉴定的人类肠道微生物基因组中预测的叶酸合成能力，以及六种人类肠道细菌门的代表性菌株的叶酸生产。细菌叶酸合成基因在512个胃肠道参考基因组中普遍存在，其中13%的基因组包含完整从头叶酸合成所需的所有基因。另外39%的基因组具有在pABA存在下合成叶酸的遗传能力，pABA是一种上游中间体，可以通过饮食或其他肠道微生物获得。通过评价选择的叶酸合成基因的表达、总叶酸产量的定量和叶酸多聚谷氨酰化的分析，在指数期和稳定期生长期间评估细菌叶酸合成。增加的关键叶酸合成基因的表达是明显的指数期，增加叶酸多聚谷氨酰化发生在后期稳定期。在叶酸生产者中，我们专注于嗜酸性罗伊氏乳杆菌，以检查与叶酸有关的宿主-微生物相互作用，并在生理学相关的人类肠模型中检查叶酸受体。RNAseq数据揭示了片段特异性叶酸受体分布。用来自野生型L. reuteri没有影响关键叶酸转运蛋白质子偶联叶酸转运蛋白（PCFT）或还原叶酸载体（RFC）的表达。而L. reuteri含有folC基因的位点特异性失活，其防止细菌在叶酸上合成聚谷氨酸尾，显著上调RFC表达。使用L. reuteri，其具有folC 2的位点失活，这导致不产生叶酸。这项工作揭示了微生物叶酸对整体叶酸状态和哺乳动物宿主代谢的贡献。
Microbial metabolites, including B complex vitamins contribute to diverse aspects of human health. Folate, or vitamin B-9, refers to a broad category of biomolecules that include pterin, para-aminobenzoic acid (pABA), and glutamate subunits. Folates are required for DNA synthesis and epigenetic regulation. In addition to dietary nutrients, the gut microbiota has been recognized as a source of B complex vitamins, including folate. This study evaluated the predicted folate synthesis capabilities in the genomes of human commensal microbes identified in the Human Microbiome Project and folate production by representative strains of six human intestinal bacterial phyla. Bacterial folate synthesis genes were ubiquitous across 512 gastrointestinal reference genomes with 13% of the genomes containing all genes required for complete de novo folate synthesis. An additional 39% of the genomes had the genetic capacity to synthesize folates in the presence of pABA, an upstream intermediate that can be obtained through diet or from other intestinal microbes. Bacterial folate synthesis was assessed during exponential and stationary phase growth through the evaluation of expression of select folate synthesis genes, quantification of total folate production, and analysis of folate polyglutamylation. Increased expression of key folate synthesis genes was apparent in exponential phase, and increased folate polyglutamylation occurred during late stationary phase. Of the folate producers, we focused on the commensal Lactobacillus reuteri to examine host-microbe interactions in relation to folate and examined folate receptors in the physiologically relevant human enteroid model. RNAseq data revealed segment-specific folate receptor distribution. Treatment of human colonoid monolayers with conditioned media (CM) from wild-type L. reuteri did not influence the expression of key folate transporters proton-coupled folate transporter (PCFT) or reduced folate carrier (RFC). However, CM from L. reuteri containing a site-specific inactivation of the folC gene, which prevents the bacteria from synthesizing a polyglutamate tail on folate, significantly upregulated RFC expression. No effects were observed using L. reuteri with a site inactivation of folC2, which results in no folate production. This work sheds light on the contributions of microbial folate to overall folate status and mammalian host metabolism.