Giant Viruses Are Ancient Living Organisms
14/09/12 13:17 Filed in: Laboratory Equipment
Submitted by S. Pelech - Kinexus on Fri, 09/14/2012
The existence of giant viruses has been known for a while now, including the fact that they can sport genomes that feature over 1 million base pairs and encode over a thousand proteins, as exemplified with the Megavirus chiliensis. Most of the larger viruses target unicellular organisms such as protozoa and algae. By contrast, some of the smallest bacteria have ten-fold smaller genomes and 5-fold less encoded proteins than these viruses. Consequently, it is not hard to envision that viruses originally evolved from invasive bacteria that eventually become mobile parasites that utilized the proteins encoded by their hosts to facilitate their own replication. With very short generation times relative to even bacteria, these early viruses underwent much faster rates of evolution to the point that some viruses, such as retroviruses, have as few as three genes. Presumably, the smaller genomes arising from the loss of non-essential genes in evolving viruses conferred a selective advantage, because they could reproduce and package their genomes faster than larger viruses. The total number of different species of bacteria on the planet is believed to be in the order of 100 million. The number of different viruses may well be in the billions.
Link to the original blog post
The existence of giant viruses has been known for a while now, including the fact that they can sport genomes that feature over 1 million base pairs and encode over a thousand proteins, as exemplified with the Megavirus chiliensis. Most of the larger viruses target unicellular organisms such as protozoa and algae. By contrast, some of the smallest bacteria have ten-fold smaller genomes and 5-fold less encoded proteins than these viruses. Consequently, it is not hard to envision that viruses originally evolved from invasive bacteria that eventually become mobile parasites that utilized the proteins encoded by their hosts to facilitate their own replication. With very short generation times relative to even bacteria, these early viruses underwent much faster rates of evolution to the point that some viruses, such as retroviruses, have as few as three genes. Presumably, the smaller genomes arising from the loss of non-essential genes in evolving viruses conferred a selective advantage, because they could reproduce and package their genomes faster than larger viruses. The total number of different species of bacteria on the planet is believed to be in the order of 100 million. The number of different viruses may well be in the billions.
Link to the original blog post