Japanese scientists discover a previously unknown giant virusprovides new insights into this enigmatic category. virus – and possibly related to the origin of multicellular life.

Researchers report that the virus was found infecting amoeba in a freshwater pond near Tokyo. The virus was named “Ushiku Virus” after Ushiku Marsh in Ibaraki Prefecture.

giant virus It was largely ignored during the first century of modern virology, and initial discoveries were often mistaken for bacteria due to their size. Still, we I almost didn’t know about their existence. Until recent decades, we Since I learned Giant viruses are all around us.

Related: Hundreds of mysterious giant viruses hidden in the ocean discovered

Viruses are generally thought of as: most abundant biological entity and some of the most complex things on earth. Little is known about the evolutionary history of viruses, and whether they are infectious remains ambiguous. recognized as a living thing.

Even though viruses are not living, it is clear that they have a major impact on all living things, including us. This includes not only taking over the host’s cells and causing disease, but also sometimes interfering with their evolution.

Viruses may facilitate it horizontal gene transfer Some organisms, known as retroviruses, insert their DNA into the host cell’s genome. If it occurs in the host’s germline, the viral DNA can be passed on to its offspring.

In fact, the remains of ancient retroviruses are now up to 8 percent The human genome has advantages. Retroviral DNA may have fed early vertebrates Ability to make myelinand that was the key Evolution of the placenta.

Long ago, viruses may have sparked an even bigger, more mysterious innovation: the evolutionary leap from prokaryotes, or single-celled organisms, to eukaryotes, or multicellular organisms.

Eukaryotic cells usually have a nucleus surrounded by a membrane,design grooveIt is unclear how such a dramatic change occurred, but one intriguing theory suggests that the nucleus was inherited from our prokaryotic ancestors. gift from the virus.

is known as Eukaryotic development of virusesthis idea was the first proposed It was announced in 2001 by Masaharu Takemura, a molecular biologist at Tokyo University of Science. He suggested that eukaryotic cell nuclei arose from large DNA viruses, such as poxviruses, that infected prehistoric prokaryotes.

Instead of causing problems, the virus takes up residence in the cell’s cytoplasm, eventually acquiring important genes from the host and gradually killing Transfer to cell nucleus.

This theory gained attention in 2003. discovery giant viruses containing DNA that form structures calledvirus factoryThese factories are sometimes surrounded by a membrane and tend to look and function much like the nucleus of a eukaryotic cell.

Scientists have since discovered a variety of giant viruses, including species in the Mamonoviridae family and the closely related Clandestinovirus, which infects certain types of amoeba. However, giant viruses are highly diverse and difficult to isolate, so new discoveries like the bovine virus have great significance.

Takemura is still studying the eukaryotic development of viruses a quarter of a century after introducing the idea, and was part of the team that identified and described Ushiku virus in a new study.

“Giant viruses can be said to be a treasure trove that the world has yet to fully understand.” (Mr. Takemura) say. “One of the future possibilities of this research is to provide humanity with a new perspective that connects the biological and viral worlds.”

Ushiku virus infects an amoeba known as Belmameba (Vermameba vermiformis), a habit shared with Clandestinovirus. Its shape and pointy capsid The surface resembles that of the medusa virus.

It is also noticeable from other giant virusesbut. For example, it causes host cells to grow abnormally large, and their capsid spikes have a unique cap and fibrous structure.

Rather than preserving the nucleus of the host cell and replicating inside it like Clandestinovirus and Medusavirus, the cowsku virus instead forms a viral factory and destroys the host’s nuclear envelope.

These similarities and differences could provide important clues that help scientists piece together the evolutionary history of giant viruses. Takemura and his colleagues want to know why and how these viruses became so diverse, and what role they played in the emergence of eukaryotes like us.

“The discovery of a new Mamonoviridae-related virus, Ushikuvirus, which has a different host, is expected to increase our knowledge and stimulate discussion about the evolution and phylogeny of Mamonoviridae,” said Takemura. say.

“As a result, we believe we will be able to get closer to the mysteries of eukaryotic evolution and giant viruses.” say.

This study Virology Journal.