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Category: Viruses and Viral Pathogenesis
Overall Issues of Virus and Host Evolution, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555817626/9781555819118_Chap01-1.gif /docserver/preview/fulltext/10.1128/9781555817626/9781555819118_Chap01-2.gifAbstract:
This chapter presents the evolution of viruses from the perspective of the evolution of their hosts. It provides an introduction to the book Viruses and the Evolution of Life that presents broad patterns for the evolution of life, evaluates the role of viruses in host evolution as well as the role of the host in virus evolution and also seeks to broadly consider and present the role of persistent viruses in evolution. Another way to think of virus evolution is to consider it from the perspective of host evolution. A chapter in this book that presents plants and insects has the unusual organization of considering the evolution of plants, insects, and their viruses all together. Another chapter is presented from an evolutionary perspective, initially addressing those animals that were first to evolve and diverge and also considering the viruses that infect them. Viruses are part of this world and have an evolutionary power that is immense and unmatched by any other living entity.
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The broad pattern of host evolution. The distribution of classified virus families among host groups is depicted. The size of each pie slice corresponds to the number of virus families. As shown here, each host group has a characteristic virus type: dsDNA for algae, Archaea, and Bacteria; dsRNA for fungi and protozoa; ds- DNA for invertebrates; negative-strand [(−)] ssRNA for vertebrates; and positivestrand [(+)] ssRNA for plants. Furthermore, the life strategies of infecting viruses also tend to correspond with host groups. For example, the viruses of hyperthermophiles and filamentous algae both have a very strong tendency to be chronic or persistent, and not lytic. The data presented here are derived from the universal database of the International Committee on Taxonomy of Viruses (http://www. ncbi.nlm.nih.gov/ICTVdb). RT, reverse transcription.
Tree-of-life dendrogram of currently accepted evolutionary relationships of all living organisms, with an overlay of color to show how the lineages support viruses. Prokaryotes are on the left and eukaryotes are on the right. These domains are connected by the LUCA, which is also identified as being viral. Highly common virus types for particular organisms are in blue. The color gradient (blue to yellow, with blue representing the most virus) identifies viral diversity for that group of organisms. Yellow indicates low viral diversity, and blue indicates high viral diversity. The LUCA is identified as being mainly viral.
Distinctions between acute and persistent life strategies of viruses a
Characteristics of virgin soil epidemics
Summary of New World epidemics
Histories of smallpox and measles epidemics
Biological characteristics of acute and persistent virus life strategies
Characteristics of fitness and persistence
Gene functions associated with persistence
Evolution of complexity and acquisition of parasitic genomic agents
Common characteristics of host and viral chromosomes a