Latvian Biomedical Research and Study Centre, Human Genetics and Disease Mechanisms Group, Ratsupites iela 1, Riga, LV-1067, Latvia.
Riga Stradins University, Dzirciema iela 16, Riga, LV-1007, Latvia.
J Med Microbiol. 2023 Jun;72(6). doi: 10.1099/jmm.0.001719.
Although the presence of micro-organisms in the blood of healthy humans is a relatively new concept, there is a growing amount of evidence that blood might have its own microbiome. Previous research has targeted the taxonomic composition of the blood microbiome using DNA-based sequencing methods, while little information is known about the presence of microbial transcripts obtained from the blood and their relation to conditions connected with increased gut permeability. To detect potentially alive and active micro-organisms and investigate differences in taxonomic composition between healthy people and patients with irritable bowel syndrome (IBS), we used the metatranscriptomics approach. We collected blood samples from 23 IBS patients and 26 volunteers from the general population, and performed RNAseq on the isolated RNA. Reads corresponding to microbial genomes were identified with Kraken 2's standard plus protozoa and fungi database, and re-estimated at genus level with Bracken 2.7. We looked for trends in the taxonomic composition, making a comparison between the IBS and control groups, accounting for other different factors. The dominant genera in the blood microbiome were found to be , , , , , , , , and . Some of these are typical environmental bacteria and could partially represent contamination. However, analysis of sequences from the negative controls suggested that some genera which are characteristic of the gut microbiome (, , , , , , , , , , , , ) are less likely to be a result of contamination. Differential analysis of microbes between groups showed that some taxa associated with the gut microbiome (, , , , , ) are more prevalent in IBS patients compared to the general population. No significant correlations with any other factors were identified. Our findings support the existence of the blood microbiome and suggest the gut and possibly the oral microbiome as its origin, while the skin microbiome is a possible but less certain source. The blood microbiome is likely influenced by states of increased gut permeability such as IBS.
虽然健康人体血液中存在微生物是一个相对较新的概念，但越来越多的证据表明血液可能具有自己的微生物组。以前的研究使用基于 DNA 的测序方法来靶向血液微生物组的分类组成，而对于从血液中获得的微生物转录本的存在及其与增加肠道通透性相关的条件的关系知之甚少。为了检测潜在的有生命和活跃的微生物，并研究健康人和肠易激综合征 (IBS) 患者之间分类组成的差异，我们使用了宏转录组学方法。我们从 23 名 IBS 患者和 26 名普通人群志愿者中采集血液样本，并对分离的 RNA 进行 RNAseq。使用 Kraken 2 的标准加原生动物和真菌数据库识别对应于微生物基因组的读数，并使用 Bracken 2.7 重新估计为属水平。我们寻找分类组成的趋势，在 IBS 和对照组之间进行比较，同时考虑其他不同的因素。血液微生物组中的优势属为 、 、 、 、 、 、 、 。其中一些是典型的环境细菌，可能部分代表污染。然而，对阴性对照的序列分析表明，一些特征性肠道微生物组的属（、、、、、、、、、、）不太可能是污染的结果。组间微生物的差异分析表明，一些与肠道微生物组相关的分类群（、、、、、）在 IBS 患者中比普通人群更为普遍。没有发现与任何其他因素的显著相关性。我们的研究结果支持血液微生物组的存在，并表明肠道微生物组可能是其来源，而口腔微生物组是可能但不太确定的来源。皮肤微生物组是一个可能但不太确定的来源。血液微生物组可能受到肠道通透性增加等状态的影响，例如 IBS。
