Viruses are ancient parasites that have influenced the evolution of contemporary and archaic forms of life
Year: 2010
Type: dissertation
Abstract: Even the simplest bacterial cell is a very complex organism that could not have emerged spontaneously within the lifetime of the Universe. Therefore the first cells were already products of evolution. However, very little is known of this primordial evolutionary process that produced the cellular organisms. Interestingly, viruses appear to have emerged before the first bacterial and archaeal cells and thus the process seem to have generated also viruses along with the cells. In this thesis a new lineage of ancient viruses (infecting solely thermophilic bacteria and halophilic archaea) was discovered. This lineage is evolutionarily related to a previously studied lineage of double-beta barrel viruses and therefore these icosahedral, inner membrane containing viruses probably separated into two lineages already before the emergence of the last universal common ancestor of cells. In order to study the possible processes that could have generated first viral genes within a primordial community of simple (RNA-based) replicators, a rule-based computing system was developed. Computational simulations suggested that the first viral-genes may have served as an information sharing mechanism between proto-cells. Possibly the modern viruses emerged from these proto-viruses while the cells evolved into more complex entities. Viruses could also have been the driving force in the isolation of the proto-cells from the primordial community since the isolation would have made the emerging cells less likely to be infected with viruses. In order to test this hypothesis, the effect of genetic isolation was studied with modern bacteria under bacteriophage selection. Bacteriophages, which exploit the gene-transfer apparatus of bacteria for recognizing the host cell, rapidly decreased the percentage of bacteria that are able to exchange genetic material with other cells. This suggests that similar isolation might indeed have occurred also on primordial conditions due to viral selection.
Author: Matti Jalasvuori
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1015540206