- 2660 - VIRUS - Could they have created life on Earth? A new virus recently discovered could be the missing link between non living viruses and living bacteria. It is called the Mimivirus because it mimics a bacterium. It is the largest virus discovered so far, about 500 nanometers long. The smallest virus is about 17 nanometers long.
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--------------------- 2660 - VIRUS - Could they have Created Life on Earth?
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- Virologists have considered viruses parasites that are much smaller than bacteria. The are not cellular and are not considered to be living organisms. They can only “live” within another living cell.
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- This discovery is challenging our biological definition of “life”. Sometime in life’s evolution on Earth life changed from chemistry to biology. Could the virus be the chemistry that did that?
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- Viruses are tiny envelopes of molecules, of protein coated DNA and RNA. DNA is deoxyribonucleic acid. RNA is ribonucleic acid. They do not have cell membranes as bacteria do. They can only replicate themselves by implanting into a living cell, usually killing the cell in the process.
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- A virus to most of us is a bad thing. The biggest selling software on the world market today is called antiviral. The word virus comes from the Latin meaning “poisonous slime“.
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- The viruses we know include the a Avian Flu virus, the Asian Flu virus, the Herpes Simplex virus that causes oral cold sores and genital herpes, the Hepatitis B virus that attacks the liver. The Coronovirus that we are just hearing about.
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- All bad critters. It is going to take a major altitudinal adjustment to begin paying homage to these critters as the precursors to all life on Earth. But, with recent discoveries that is the school of thought that has come forward.
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- Biologists have not considered the virus to be a living organism. Biologists define three branches of life: eukaryotes, bacteria, and archea.
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-------------------------- Eukaryotes are organisms whose cells have a nucleus.
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-------------------------- Bacteria are single celled organisms that may or may not have a nucleus.
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-------------------------- Archea are microbes that do not have a nucleus, yet they make up 33% of all life on Earth.
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- Viruses depend on these living organisms in order to survive, they are parasites that do not have cell membranes of their own. Biologists have categorized over 4,000 different types of viruses.
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- But, there are millions more that have not been categorized. A geneticist circled the globe in his sailboat and sampled the water every few hundred miles. Within every sample he discovered millions of new viruses.
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- Most of these viruses are integral to life and are harmless to us. Each of us is infected with a huge array of viruses with no ill effects. The biological information in an organism is encoded in an RNA or DNA sequence. All the encoding in a cell is called the genome.
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- The human genome contains more retrovirus sequences than actual genes. Biologists consider these sequences to be junk code. They persist and replicate but do not do anything. Yet, they are there, part of our genetic identity.
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- There are so many viruses on Earth that if you stacked them head to toe they would stretch out 58,800,000,000,000,000,000 miles. That is 10 million light years long. There are more viruses on Earth than there are stars in the Universe.
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- Most people only think viruses are HIV and flu but in fact most of the genetic material on Earth are viruses.
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----------------------------- Viruses have different ways of replicating:
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- The Yellow Fever virus is an RNA virus that can replicate itself without DNA. The HIV virus, Human Immunodeficiency virus, uses its own RNA to create a strand of DNA that it splices into a host’s genome.
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- The Hepatites B virus is a DNA virus that transmits through the blood. The Rhinovirus that causes the common cold has no external envelope making it more contagious to humans.
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- The Parainfluenza Type 1 virus that causes respiratory infections attaches to the host cell using small hooks and spikes.
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----------------------------- Viruses come in all shapes and sizes:
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- The Herpes Simplex virus has a geometric 20-sided structure. The Polio virus has a spherical shape and looks like little BB’s. The Tobacco Mosaic virus looks like a heap of spilled pick-up sticks. It was the first virus ever discovered in 1935 after the invention of the electron microscope.
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- The West Nile virus has a cube-shaped capsid. The capsid is the outer protein coating that is common to all viruses.
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- The Mimivirus was discovered in 2003 in an industrial cooling tower in the West Yorkshire mill town of Bradford, England. The bacteriologists were looking for Legionella, a bacterium that causes a sever pneumonia-like disease known as Legionnaire Disease. Some of the Legionella bacteria they found were difficult to examine.
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- Later it was discovered that these bacteria were occupied by the Mimivirus. The Mimivirus has turned out to be the largest ever found. It was 500 nanometers in length. Visible light wavelengths, from blue to red, are from 400 to 700 nanometers long, so this virus was just the size of one wavelength and could actually be seen with a light microscope.
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- Most viruses are 1/10 that size and require an electron wave microscope in order to see them. The genome in this Mimivirus is 1,200,000 letters long, 10 times larger than a typical virus, and, even larger than some parasitic bacteria.
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- The light microscopes can magnify up to 500 to 1000 times and can resolve down to 200 nanometers. The electron microscope using electron wavelengths can magnify up to 500,000 to 2,000,000 times and resolve down to less than a tenth of a nanometer.
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- With the discovery of the Mimivirus the boundary between non living viruses and complex living bacteria has become blurred.
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- RNA virus are thought to be at the base of the tree of life before today’s DNA based organisms evolved. These RNA virus make copies of themselves with much more errors and mutations. These variations allow the virus to have a resiliency to adapt.
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- The Mimivirus is believed to be an ancient lineage of a DNA virus. Its soccer ball shape has infected all three of the life forms, eukaryotes, bacteria and archaea. And is therefore believed to have emerged prior to these three life forms.
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- At life’s earliest evolution could a Mimivirus have entered a bacterium and persisted there. Could the bacterium become the cell and the cell begin replicating? Could that have been the earliest form of life?
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- February 17, 2020 1750 2660
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--------------------- Monday, March 9, 2020 -------------------------
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