The Norovirus: A Study in Puked Perfection
, "Each norovirus carries just nine protein-coding genes (you have about 20,000). Even with that skimpy genetic toolkit, noroviruses can break the locks on our cells, slip in, and hack our own DNA to make new noroviruses. The details of this invasion are sketchy, alas, because scientists haven’t figured out a good way to rear noroviruses in human cells in their labs. It’s not even clear exactly which type of cell they invade once they reach the gut. Regardless of the type, they clearly know how to exploit their hosts. Noroviruses come roaring out of the infected cells in vast numbers. And then they come roaring out of the body. Within a day of infection, noroviruses have rewired our digestive system so that stuff comes flying out from both ends." [more inside]
posted by Blasdelb
on Jan 3, 2013 -
"Why do parasites harm their hosts? Conventional wisdom holds that because parasites depend on their hosts for survival and transmission, they should evolve to become benign, yet many parasites cause harm. Theory predicts that parasites could evolve virulence (i.e., parasite-induced reductions in host fitness) by balancing the transmission benefits of parasite replication with the costs of host death. This idea has led researchers to predict how human interventions—such as vaccines—may alter virulence evolution, yet empirical support is critically lacking." Two papers
demonstrate empirical evidence for related models predicting the origin of virulence: [more inside]
posted by Blasdelb
on Oct 21, 2012 -
Provirophages and transpovirons as the diverse mobilome of giant viruses
Abstract: A distinct class of infectious agents, the virophages1 that infect giant viruses of the Mimiviridae family, has been recently described. Here we report the simultaneous discovery of a giant virus of Acanthamoeba polyphaga (Lentille virus) that contains an integrated genome2 of a virophage (Sputnik 2), and a member of a previously unknown class of mobile genetic elements3, the transpovirons4. The transpovirons are linear DNA elements of ∼7 kb [kilobases]5 that encompass six to eight protein-coding genes, two of which are homologous6 to virophage genes. Fluorescence7 in situ hybridization8 showed that the free form of the transpoviron replicates within the giant virus factory and accumulates in high copy numbers inside giant virus particles, Sputnik 2 particles, and amoeba cytoplasm. Analysis of deep-sequencing data showed that the virophage and the transpoviron can integrate9 in nearly any place in the chromosome of the giant virus host and that, although less frequently, the transpoviron can also be linked to the virophage chromosome. In addition, integrated fragments of transpoviron DNA were detected in several giant virus and Sputnik genomes. Analysis of 19 Mimivirus strains revealed three distinct transpovirons associated with three subgroups of Mimiviruses. The virophage, the transpoviron, and the previously identified self-splicing introns10 and inteins11 constitute the complex, interconnected mobilome12 of the giant viruses and are likely to substantially contribute to interviral gene transfer.
[Full Text PDF
] and two explanations in English [more inside]
posted by Blasdelb
on Oct 16, 2012 -
"There may be no biological process more complicated than the relationships that viruses have with their hosts. Could it be that their persistence made it possible for humans to thrive?" [Via Disinformation.]
posted by homunculus
on Nov 27, 2007 -
A monstrous discovery
suggests that viruses, long regarded as lowly evolutionary latecomers, may have been the precursors of all life on Earth.
"We haven't even begun to scratch the surface. The numbers are mind-boggling. If you put every virus particle on Earth together in a row, they would form a line 10 million light-years long. People, even most biologists, don't have a clue. The general public thinks genetic diversity is us and birds and plants and animals and that viruses are just HIV and the flu. But most of the genetic material on this planet is viruses. No question about it. They and their ability to interact with organisms and move genetic material around are the major players in driving speciation, in determining how organisms even become what they are."
posted by five fresh fish
on Feb 17, 2006 -