Bush of life: how giant viruses attack (Introduction)

by David Turell , Tuesday, May 26, 2020, 23:33 (1424 days ago) @ David Turell

More research on how they release their DNA. Like all viruses they lack RNA and cannot replicate without it:

https://www.livescience.com/triggers-for-giant-virus-infection.html?utm_source=Selligen...

"Viruses, giant or otherwise, lack the machinery required to make copies of their DNA; the microbes are essentially just a coil of genetic material tucked inside an envelope, called a capsid. In order to survive, viruses must sneak inside a host cell, hijack the machinery within and set up a so-called viral factory to produce new viruses. Giant viruses have a special portal for this job: the stargate.

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"Since their initial discovery, giant viruses have been recovered from melting permafrost in Siberia, the depths of the Antarctic ocean and highly alkaline soda lakes, as well as less exotic environments, said Chantal Abergel, research director of the Structural and Genomic Information laboratory at the French National Centre for Scientific Research, who was not involved in the study. The viruses have mostly been found to infect amoebas and phytoplankton, but laboratory studies suggest that they can also infect animal cells, including rodent and human cells. However, "no direct link between GVs and human disease has yet been established," the authors noted.

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"For example, Parent and her coauthors studied several giant viruses that look like 20-sided dice, including the mimivirus, Antarctica virus, Samba virus and Tupanvirus. The structure and outer shells of these viruses "are very complex, as never seen before in the virosphere," Jônatas Abrahão, an associate professor of virology at the Universidade Federal de Minas Gerais in Brazil, told Live Science in an email. The stargate found on the surfaces of these viruses particularly fascinates scientists "due its beauty and symmetry," and the fact that no smaller viruses contain such a structure, said Abrahão, who was not involved in the study.

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"Before the stargate opens, giant viruses get "gobbled up by cells" in a process called phagocytosis, Parent said. While small viruses like influenza fuse their fatty membrane with that of the cell they're infecting, giant viruses enter cells by being swallowed whole, hard outer shell and all.

"Once inside, the giant viruses open their stargates and release their infectious "seed," Abergel said. "This is an entire structure that is downloaded from the plasmid," or circular ring of viral DNA, into the cytoplasm, or the water solution of proteins and salts that surrounds the organelles in eukaryotic cells. This process jumpstarts infection, she said."

Comment: The complex parts of the giant virus suggest it is a more evolved form of virus.