Unfamiliar life - giant virus

Bacteria are still viruses

In 1992, a mysterious microbe was found in the water tower of Bradford, in the north of England. Under the microscope, no matter how, the microbes are very strange, this is a hairy polyhedron, there are 20 faces, these features suggest that it is a virus. But the experts think it is just a kind of bacteria, because compared to the virus found before, its individual seems too big.

This is the first time a giant virus has come out, but it is only regarded as an unclassified bacterium, and then trapped in the freezer, was forgotten.

Until 1998, the French scientist Bernard took it out and watched it look. Bernard is very interested in it, because it does not have ribosomes, and ribosomes are the factories that make proteins, and proteins are a hallmark of all cell life. More importantly, this kind of microorganism does not carry out cell propagation like bacteria. So it must be a virus.

In 2003, the French Marseille School of Medicine Jean Mitchell Crawley in the study led to "Legionnaires disease" of the "Legionella", once again found the virus, through genetic sequencing, it was officially identified as giant virus , Known as the rice virus (Mimivirus, meaning the bacteria like bacteria).

This newly discovered living body is not the same as a typical bacterium or cell, and it does not divide into two, but produces hundreds or even more new virus particles. It has some of the other viruses found in the function, for example, it can messenger RNA (mRNA) into protein, but also to create their own 150 kinds of protein.

Springing up

And the researchers at the same university as Clarkley, who was very interested in it, began to look for giant viruses and set the target in the environment where the giant virus first appeared: the water tower. Sure enough, he found another giant virus in the water tower in Paris, and named "Mamavirus" (Mamavirus). The biggest surprise is that Laoer Te found a virus in her mother's virus - it is the first time scientists have seen a virus infected with another virus. This discovery shows that to some extent the virus is alive, because the mother virus will be "sick."

In 2010, Laurent conducted a more extensive search, found a total of 19 kinds of giant viruses, which appeared in rivers, lakes, fountains, faucet water. In this way, giant virus like mushrooming in succession in front of people.

A year later, Crawley found a bigger virus in Chile's oceans and named it "Megavirus". Million viruses seem to be distant from the Mimi virus, in addition to having many of the same genes with the rice virus, but also more out of some unique genes. They are very similar in appearance, but millions of viruses than the rice virus virus nearly 6.5%.

Then, the Crawford research team discovered Pandoravirus almost simultaneously in a pond silt in Australia and in the river mud of Chile. One of them has about 1,500 genes and the other has 2550 genes.

Then there may be some of the most impressive specimens. In 2014, Crawley found another giant virus in an ice-ice sample of ice-tonight 30,000 years ago. It had an opening at one end and looked like an elongated jar underneath the microscope. - Siberian Pantovirus. It is about 1.5 microns longer than the previous body record holder Pandora virus even bigger. The most terrible is that it is still contagious, but its goal is only amoeba. Due to its strong ability to survive, was ridiculed for the long live old man.

At this point, scientists have realized that giant viruses may be ubiquitous, and in various forms.

Transboundary giant virus

Biologists have been reluctant to put the virus in the ranks of life because they are almost impossible to live independently, they are "parasites", their own genetic instructions "invade" to other biological host cells, and hijack the host cell this "Biochemical machines" for their production of the next generation of parts needed. Many viruses will only do one thing, that is to copy themselves, which means that they can not need a lot of genes. For example, the number of human immunodeficiency virus (HIV) genes is only nine. In contrast, the giant virus gene number is quite, there are 1018 meters of the virus.

On the other hand, from the giant virus gene sequence, they are likely to have the ability to independently reproduce. Later, although the loss of this ability, but now also retain many self-reproduction must be "equipment".

So, what is the problem with biologists: what kind of biological system should they be divided into?

The giant family history of the virus can be traced back to about 3.3 billion years ago. At that time, the early life of the Earth's form of life is gradually divided into eukaryotes and prokaryotes. In 1977, scientists divided organisms into "three domains" systems: eukaryotes, bacteria and pungent bacteria. Eukaryotes are composed of cells, such as animals and plants, and genes are neatly "encapsulated" within the nucleus. Bacteria are prokaryotes, no nuclei, cell structure is relatively simple. Paleobacteria are similar to bacteria, but some chemical characteristics are different. These three domains basically consist of all creatures.

Strangely enough, it does not seem appropriate to put them on the giant virus gene. The 50% to 90% of the giant virus gene is essentially unique, and scientists have not been observed in other organisms, and even different types of giant viruses do not share genes. Such as the rice virus, which itself can acquire genes from its host cells, but its genes are distinct from the genes of their host amoeba and other cells. Obviously it is out of the "three domains" of the community.

New life branch

So scientists put forward a new hypothesis: in the biological system, giant virus originated in the already extinct life branch (domain), and may be a number of branches, life forms of diversification, but with the cells are now completely different.

These life branches appear earlier than the time of occurrence of the three main life branches (or life domains) of bacteria, archaea and eukaryotes. This means that the age of the giant virus is greater than the virus we are familiar with.

In 2012, scientists created phylogenetic trees based on viruses and cells with similar protein structures and categorized. As a result, the giant virus seems to be more ancient than any creature. The results support the hypothesis that they come from the extinct ancient life domain.

Although the evidence is not enough to persuade other scientists to hold objections, but it is certain that we can no longer say that the virus is not life.

Very unfriendly?

The giant virus may be around us, and there is evidence that they are wandering in our bodies, such as human blood. Do they have a threat to mankind?

So far, scientists have found that most of the giant viruses can infect amoeba, but have not yet found that they will have any significant threat to humans. In 2014, French evolutionary geneticists found that the giant virus's 23 genes appeared in other cellular organisms, including moss and gel-like freshwater faucets. In fact, this suggests that in addition to amoeba, the giant virus may have many other hosts. In addition, some studies have found that they are associated with pneumonia and other diseases. This leads some people to think that giant viruses play a role in human disease.

The knowledge of giant virus remains to be further studied by scientists.