Image source @ Vision China
Do you know how many microbes live in your body?
You may not believe it,
It can be said that the biological diversity of human intestines, scientists are incredible. In addition to bacteria, there are thousands of viruses, especially phages, which can infect bacteria.
Fig. phages on intestinal bacteria (source: Spencer Phillips / embl-ebi)
In recent years, the research on human intestinal microorganisms has become a hot field. Scientists have also confirmed that the imbalance of intestinal microbiota can lead to diseases and complex symptoms, such as inflammatory bowel disease, allergy, obesity, and even affect the development and treatment of cancer and neurological diseases.
But to be honest, scientists' understanding of the role of intestinal bacteria and enteroviruses in human health and disease today is only the tip of the iceberg.
On February 18, 2021, the top journal Cell published a great achievement. Researchers from Wellcome Sanger Institute and embl-ebi analyzed more than 28000 intestinal microbiome samples collected in different regions of the world,More than 140000 viruses have been identified in the human gut, and more than half of them have never been seen before.
The researchers said the number and diversity of human enteroviruses they found were staggering, and the data opened up a new way to understand how enteroviruses affect human health.
Sequence 140000 viruses in the human body
As mentioned above, there are trillions of microorganisms in the human body. It is not easy to identify the specific types of these microorganisms. Previous analysis techniques mostly focused on virus fragments with limited resolution to characterize a single phage genome or connect specific phages with bacterial host species, so it is difficult to identify all kinds of viruses.
Metagenomics（metagenomics）。 Metagenomics directly measures all DNA sequences of a microbial ecological environment through high-throughput sequencing, and then analyzes and identifies all species information in this ecological environment.
Researchers from weikonsanger Institute and European Bioinformatics Institute analyzed 28060 common human intestinal metagenomes and 2898 bacterial genomes isolated from healthy human intestines through high-throughput sequencing of metagenomics DNA.
The results of this study form an intestinal phage database (GPD) containing 142809 non redundant phage genomes. By classifying the biodiversity of virus species, the researchers identified more than 140000 kinds of viruses that live in human intestines, more than half of which have never been seen before.
In order to further improve the quality of data sets,The researchers also designed a machine learning method to filter the effects of pollutants.
Fig. distribution of bacterial host range of intestinal phage. Host distribution showed that Firmicutes phyla had the highest virus diversity, and about 36% of virus clusters (VCS) were not limited to a single species.
In addition, the researchers also found that human lifestyle is related to the intestinal distribution of bacteriophages in different regions of the world, and the bacterial composition of individual microbiome can affect the composition of intestinal bacteriophages.
For example, prevotellaceae bacteria are more abundant and common in rural / traditional lifestyle individuals, while Bacteroides are more abundant and common in urban / Western lifestyle individuals. Using the host allocation data for each phage, the researchers found that,In Africa, South America and Fiji metagenome samples, the prevotellaceae family was significantly higher than that in North America, Europe, Asia and Australia; on the contrary, Bacteroides phages were significantly more common in North America, Europe, Asia and Australia.
Fig. global intestinal phage branches and their bacterial hosts
This collection represents the most comprehensive and complete set of human intestinal phage genomes to date and complements other published intestinal phage databases, the researchers said in the paper.
what's more,The establishment of a comprehensive and high-quality phage genome database paves the way for a large number of human enterovirus genome analysis.This will be a valuable resource for scientists studying bacteriophages and their role in regulating intestinal bacteria and our own health.
To some extent, viruses are not living things. Because virus is a kind of non cellular life form, small in size and simple in structure, it contains only one kind of nucleic acid (DNA or RNA) and must parasitize in living cells and proliferate by replication.
According to statistics, about 70% of human infectious diseases are caused by viruses.
The Justinian plague in the 6th century, originated from a kind of lethal Yersinia pestis, was widely spread among wild gnawing animals. It originated in the Sinai Peninsula of Egypt. With the help of human trade and migration, it spread to all European countries and wiped out 17% of the world's population at that time.
In the 14th century, the same plague swept across Europe from Central Asia to the west along the Silk Road, killing 25 million people in Europe alone. This is the famous black death in history.
The outbreak of influenza in 1918 completely swept the world, killing about 20 million to 50 million people worldwide. Among them, the death rate of young people aged 20 to 40 is the highest. Because of the first World War, the highly concentrated allied and allied forces confronted in the trenches, and the frequent flow of personnel promoted the spread of influenza virus.
Figure 1918 pandemic
There is no doubt that the 1918 pandemic cast a long shadow over the 20th century.
The mention of the outbreak of SARS in 2003 still leaves us with a lingering fear. SARS, also known as severe acute respiratory syndrome (SARS), is an acute respiratory infectious virus caused by SARS coronavirus (SARS CoV). The main mode of transmission is close droplet transmission or contact with respiratory secretions of patients, with a mortality rate of nearly 11%. It started in Guangdong and spread rapidly to Hong Kong through tourism, trade and immigration, and then to Southeast Asia and even the world.
Currently,The epidemic of pneumonia caused by New Coronavirus is rampaging around the world. The most mysterious creature on the planet has once again received great attention.From SARS to Ebola virus, to the current new coronavirus, the virus seems to be in danger, constantly challenging and threatening the safety of human life.
Although scientists have been racing against the virus for a long time, so far, we still have too many unknowns to explore.
For example, early last year, scientists found a mysterious virus in an artificial lake in Brazil. Its genome is almost new to scientists, and it has never been recorded in human virus research. Scientists have named the virus Yara virus, the mythical water queen of Brazil, which is both daunting and magical.
Infection of amoeba with tuyala virus (dark color) (source: Science)
so far,Scientists have found thousands of new viruses hiding in dozens of animals. In addition, scientists also found evidence of the existence of ancient viruses in ice core samples from the Qinghai Tibet Plateau, of which 28 are new viruses. With global warming, glaciers around the world are shrinking, which may release microorganisms and viruses that have been frozen for tens of thousands or even hundreds of thousands of years.