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Are viruses alive? Or are they simply inanimate machines made up of nucleic acids surrounded by a protective coat of protein? They lack the enzymes needed to carry out the chemical reactions for life, so they cannot replicate outside of an
already living cell. They are also incredibly small, and their biological history is misunderstood, since they do not form fossils. But they have had an incredibly huge impact on all living things.
Recent studies have changed the perception of more complex viruses. Scientists began to look at the three-dimensional structural domains of proteins in living organisms from all trees of life (including bacteria, archaea, and eukaryotes) to study their evolution. These structural designs (or folds) are relatively stable molecular fossils that tell the story of past evolutionary events. Certain protein folds are unique to small numbers of specific organisms, while others are found in practically all living things. It is assumed that the more common a protein fold is across various groups of organisms, the more ancestral it must be.
Since some giant viruses have genomes that rival the size of those in some bacteria, they were included in the study. Surprisingly, these giant viruses were found to have many of the same common protein folds found in most other organisms, meaning they were rooted in the very earliest stages of evolution. They were also found to harbor enzymes involved in translating the genetic code into proteins… which is astonishing, given that viruses lack all other enzymes needed to complete the protein building process. Turns out viruses share a lot more with living things that we originally thought, and scientists now believe that ancient viruses were probably much bigger and much more complex, and their genome was simplified over time.
Source:http://www.sciencedaily.com/releases/2012/09/120913123520.htm
Recent studies have changed the perception of more complex viruses. Scientists began to look at the three-dimensional structural domains of proteins in living organisms from all trees of life (including bacteria, archaea, and eukaryotes) to study their evolution. These structural designs (or folds) are relatively stable molecular fossils that tell the story of past evolutionary events. Certain protein folds are unique to small numbers of specific organisms, while others are found in practically all living things. It is assumed that the more common a protein fold is across various groups of organisms, the more ancestral it must be.
Since some giant viruses have genomes that rival the size of those in some bacteria, they were included in the study. Surprisingly, these giant viruses were found to have many of the same common protein folds found in most other organisms, meaning they were rooted in the very earliest stages of evolution. They were also found to harbor enzymes involved in translating the genetic code into proteins… which is astonishing, given that viruses lack all other enzymes needed to complete the protein building process. Turns out viruses share a lot more with living things that we originally thought, and scientists now believe that ancient viruses were probably much bigger and much more complex, and their genome was simplified over time.
Source:http://www.sciencedaily.com/releases/2012/09/120913123520.htm