Viruses are Alive, and They Share An Ancestor With Modern Cells - Dream Health

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Tuesday 6 October 2015

Viruses are Alive, and They Share An Ancestor With Modern Cells


Viruses – Living Entities/Share Common Ancestor with Cells

Evolutionary biologist are on discussions that the viruses seem to belong to the tree of life, in the universe and have put a case forward for viruses sharing common ancestor with the other cells. The debate is that viruses should not qualify as living entities and that they are not `alive’ since they tend to lack a true metabolism and does not reproduce on their own.

Published in Scientific Advances, Arshan Nasir and Gustavo Caetano-Anolles’s paper – A phylogenomic data driven explorations of viral origins and evolution has challenged this. They state that `virus factories’ structures formed by various giant viruses within the cells they infect are cell-like organisms, strikingly familiar to several intracellular parasitic bacterial which also depend on host metabolism to reproduce’.

These types of bacteria are considered as living things though very simple and researchers claim that virus factories should be regarded as the true `self’ of a virus and the infectious virions to be considered as gametes which then go on to `fertilise’ other cells by infecting them. Taking this into account, viruses could be eligible to form the evolutionary tree of life and take their stand along with the cells.

Viruses Transform/Genetic Codes Change

Nasir and Caetano-Anolles had found the possibility to identify the ancestry as well as the evolution of viruses, describing `proto-virocells which harboured segmented RNA genomes and existed with the ancestors of modern cells. In order to learn more on how viruses could be related to cells, evolutionary biologist Gustavo Caetano-Anolles and Arshan Nasir compared the protein folds of 3,460 viruses with 1,620 cells.

Folds seems to be the basic structures which give proteins their complex shapes and the genetic codes of all cells and the viruses carry instructions for the various protein folds. Comparing them seems a good way of studying evolutionary history particular in viruses.

Most of the viruses often transform and their genetic codes change quickly which could cover the oldest genetic traces. However, protein folds keep their shapes even when their genetic codes seem to change. This makes them a good record of viruses and cells ancient evolutionary history.

True Self of Virus – Intracellular Virus Factory of Infected Cells

Viruses which were analysed by Caetano-Anolles and Nazir turned out to share 442 protein folds with the cells in the study. They also found 66 protein folds which were probably unique to viruses. It was what the biologist basically expected to discover when they compared two related organisms, with a large number of familiarities with a few variations to set the two organisms apart.

 As per Caetano-Anolles and Nasir these discoveries indicate a shared origin for cells and viruses. According to them to determine if the viruses could reproduce and have metabolism it is essential to look at the `virus factory within an infected cell instead of what in usually thought of as the body of a virus, particles known as virions which prevail outside cells, do not reproduce.

They write that the true self of a virus is the intracellular virus factory of infected cells and not the virion. An infected cell tends to reproduce by producing new virions which affect other cells in order to make new virus factories.

Caetano-Anolles and Nasir state that the process is similar to how conventional organisms produce gametes to fertilize other cells and reproduce. Infected cells also tend to produce proteins that fall in the category of production of new virions.

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