Vital Marius, Rud Tatjana, Rath Silke, Pieper Dietmar H, Schlüter Dirk
Institute for Medical Microbiology and Hospital Epidemiology, Hannover Medical School, 30625 Hannover, Germany.
Microbial Interactions and Processes Research Group, Helmholtz Centre for Infection Research, 38124 Braunschweig, Germany.
Comput Struct Biotechnol J. 2019 Jul 26;17:1016-1019. doi: 10.1016/j.csbj.2019.07.012. eCollection 2019.
The secondary bile acids deoxycholic acid (DCA) and lithocholic acid (LCA), formed by gut microbiota from primary bile acids via a multi-step 7α-dehydroxylation reaction, have wide-ranging effects on host metabolism and play an important role in health and disease. A few 7α-dehydroxylating strains have been isolated, where bile acid-inducible () genes were organized in a gene cluster and encoded major enzymes involved. However, only little is known on diversity and abundance of intestinal bacteria catalysing DCA/LCA formation in the human gut . In this study, we took the opportunity to screen metagenome-assembled genomes (MAGs) from sequence data of stool samples provided by two recent studies along with newly available gut-derived isolates for the presence of the gene cluster. We revealed in total 765 and 620 MAGs encoding the potential to form DCA/LCA that grouped into 21 and 26 metagenomic species, respectively. The majority of MAGs (92.4 and 90.3%) were associated with a clade that still lacks an isolate, whereas less MAGs belonged to along with eight new isolates (n total = 11) that contained the genes. Only a few MAGs were linked to . Signatures for horizontal transfer of genes were observed. This study gives a comprehensive overview of the diversity of -exhibiting bacteria in the human gut highlighting the application of metagenomics to unravel potential functions hidden from current isolates. Eventually, isolates of the identified main MAG clade are required in order to prove their capability of 7α-dehydroxylating primary bile acids.
次级胆汁酸脱氧胆酸（DCA）和石胆酸（LCA）由肠道微生物群通过多步7α-脱羟基化反应从初级胆汁酸形成，对宿主代谢具有广泛影响，在健康和疾病中发挥重要作用。已经分离出一些7α-脱羟基化菌株，其中胆汁酸诱导型（）基因在一个基因簇中组织并编码相关的主要酶。然而，对于人类肠道中催化DCA/LCA形成的肠道细菌的多样性和丰度知之甚少。在本研究中，我们利用机会从最近两项研究提供的粪便样本序列数据中筛选宏基因组组装基因组（MAG），以及新获得的肠道来源分离株，以寻找基因簇的存在。我们总共发现了765个和620个编码形成DCA/LCA潜力的MAG，分别归入21个和26个宏基因组物种。大多数MAG（92.4%和90.3%）与一个仍缺乏分离株的进化枝相关，而较少的MAG属于，还有8个新分离株（总共n = 11）含有基因。只有少数MAG与相关。观察到基因水平转移的特征。这项研究全面概述了人类肠道中具有特征的细菌的多样性，突出了宏基因组学在揭示当前分离株隐藏的潜在功能方面的应用。最终，需要鉴定出的主要MAG进化枝的分离株，以证明它们对初级胆汁酸进行7α-脱羟基化的能力。
