Scientists have described the microbiome of blood
Oleg Lischuk, N+1
American, Dutch and Finnish scientists have found that a microbiome is present in the blood of healthy people and patients with various diseases. It also turned out that in schizophrenia, the microbial composition of the blood is highly diverse. A preprint of the study is published on the bioRxiv service (Mangul et al., Total RNA Sequencing reveals microbial communities in human blood and disease specific effects).
Employees of the Universities of California in Los Angeles, Davis and San Francisco with colleagues from other research centers collected blood from 192 people. The sample included 49 healthy people, as well as 48 patients with schizophrenia and bipolar disorder and 47 people with amyotrophic lateral sclerosis.
Complete RNA sequencing was performed in all whole blood samples. Readings characteristic of the human genome and transcriptome, as well as low-quality or too simple readings were excluded from the data obtained. The remaining qualitative data, presumably belonging to representatives of the blood microbiota, were used for phylogenetic and taxonomic analysis using marker genes.
On average, 1,235 readings (1.24 percent) from each sample were attributed to bacterial or archaeal gene families. In total, 1880 microbial taxa belonging to 23 biological types were found in the examined blood (an average of 4.1 ± 2 types in each person). Most of them belonged to bacteria, the rest to archaea. There were no signs of the presence of eukaryotes and viruses in the samples. To exclude the possibility of microbial contamination of the samples, the analysis protocol was tested on samples of sterile and pathogen-infected cell lines.
Proteobacteria type bacteria were found in all the examined patients, which dominated most of the samples. Firmicutes and Cyanobacteria types were also common – they were found in at least a quarter of samples from each group.
The revealed microbial composition was compared with microbiomes of other organs (intestines, oral cavity, respiratory tract and skin) using 499 metagenomic samples obtained as part of the Human Microbiome Project. Scientists were able to find a match for 15 types of microorganisms, which indicate that the dominant taxa of the blood microbiome are most closely related to the microbiota of the mouth and intestines.
After adjusting for gender, age and technical factors, it turned out that there were no significant differences between the blood microbiomes of healthy people, patients with bipolar disorder (BPD) and amyotrophic lateral sclerosis (ALS), and in schizophrenia (SCZ) it has a much more diverse composition.
Types of bacteria and archaea in blood samples (figure from the article in bioRxiv)
The diversity was non-specific, that is, not related to the predominance of a certain microbial profile. These data were reproduced in an additional study, but their clinical significance remains unclear.
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09.06.2016