Monday, July 22, 2013

Fourth domain for a new form of life

The famous anecdote "On board the space station discovered a giant virus that infected Soviet cosmonaut" may be not so absurd: Biologists have discovered a virus of such size that they have no right to believe in it.

Initially called it simply - NLF, a new form of life (New Life Form). Strange body, a dedicated French microbiologist from sea water samples, pick up off the coast of Chile, infects the simplest - amoebas. Soon, the same body showed up and in Australia.

Under a microscope, they look like a small bacterial cell - large and dark round spots. However, it is not bacteria. The study has shown them that the NLF - viruses, the largest of all known, reaching 1 m in the longest dimension and 0.5 in the short. And their genome (1,900,000 nitrogenous bases for the "Chilean» NLF and 2.5 million for the "Australian") in size corresponds to the most complex bacterial genomes - or the simplest eukaryote genomes.

However, there is not even the main dimensions sequencing revealed that no more than 7% NFL genes have counterparts in other organisms. Scientists believe that they have managed to stumble on a completely unknown before - a fourth, in addition to the Achaean, bacteria and eukaryotes - branch tree trunk on earthly life. The authors find no secret surprise: "What kind of unknown genes and how do they work? Again, we are opening a Pandora's Box. "

Apparently, so the newly found NLF received an appropriate name – Pandora virus. The very fact of finding them on different continents shows that they can be quite common on the planet. Moreover, a similar body was discovered by the German physician Rolf Michel (Rolf Michel) in 2008 within the amoeba, rinse with contact lenses woman sick of hepatitis. Then the scientist found it a bacterium that inhabits the amoeba as a parasite or symbiotic. Now he admits that the body is almost identical to the description found by the French Pandora virus. "Who would have thought that these organisms are giant viruses" - he says.

However, this virus is in the full sense of the word: they show no signs of what might be called a living cell, they are unable to self-protein synthesis, production of energy in the form of ATP, divide and reproduce outside a host cell. In other words, it is the intracellular parasites, as well as all normal viruses. Studies have shown that the life cycle of these giants is quite common for viruses: Pandora virus amoeba infects a cell, it releases its proteins and DNA, "captures" the biochemical machinery of it, with the help of which produces and releases hundreds of copies of itself.

However, from this Pandora virus are only interesting for the study. What are the unknown 93% of their genome? What are the proteins they encode? And most importantly, where they all come from? According to some experts, it can be degraded full-cell organisms. They believe that once life on Earth consisted of a lot more "trunk" than the three currently available, but most of them have either disappeared or survived only as a pale shadow of parasitic   - Viruses, one of which managed to stumble and French biologists.

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