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5 December 2013 11:26 am ,
Vol. 342 ,
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Pathogenic Cousins of Mitochondria
11 November 1998 7:00 pm
Scientists may have identified the closest living relative of the organism that eventually turned into mitochondria, the organelles that power all eukaryotic cells. The sequence of Rickettsia prowazekii, the pathogen that causes typhus, closely resembles that of mitochrondrial DNA, researchers report in tomorrow's issue of Nature. Tracking down the genes that make the bug so deadly may lead to better vaccines against R. prowazekii, which causes high fever and delirium.
It took 6 years for molecular microbiologist Charles Kurland of the University of Uppsala in Sweden and his colleagues to sequence the 1.1-million-base-pair genome of R. prowazekii. Already, preliminary genetic analyses had suggested that its genome might closely resemble that of the predecessor of a prisoner of cells, the mitochondria. Indeed, a comparison with the DNA still present in modern mitochondria has revealed "very strong similarities," says team member Siv Andersson, particularly in genes involved in energy production.
Many of the pathogen's 834 genes closely resemble those that code for proteins used by yeast mitochondria--genes that are located in the nucleus of yeast cells. This suggests "an early evolutionary event where there was an off-loading of these genes" from the early mitochondrion to the nucleus, says Kurland. As the ancestral host nucleus took on these genes, the mitochondria would have become more dependent on the host cell, until eventually they could no longer survive except within the cell.
Assuming that scenario is correct, the work "is a wonderful study in the way genomes evolve to become degenerate," says evolutionary biologist Carl Woese of the University of Illinois, Urbana. It could also lead to practical payoffs, because a half-dozen genes in the Rickettsia genome code for proteins similar to those that make other bacteria virulent. Three resemble genes for toxic polysaccharides in Staphylococcus aureus, which causes boils. The information should help researchers interested in developing new vaccines for typhus find the right proteins to include in their inoculations, Kurland says.