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A Tale of Two Genomes: One a Permanent Mutator, the Other a Flesh Eater

NEW YORK, Jan. 14 — A newly finished sequence of the genome of a hyperthermophilic crenarchaeon has given researchers a glimpse of life under extreme conditions, while the sequence of another genome—believed to be the first annotation of its kind—lets scientists better understand a nasty flesh-eating bacterium.


Both sequences are published in the Jan. 22 issue of the Proceedings of the National Academy of Science.

Pyrobaculum aerophilum, the hyperthermophilic crenarchaeon, is a bacteria-like microorganism uniquely adapted to life in seawater whose temperature is roughly to 100 degrees Celcius. Unlike its evolutionary cousins, however, it is not purely anaerobic and cannot tolerate the presence of sulfur.


The scientists, a team from the University of California at Los Angeles, Cal Tech, and Germany's Regensburg University, found the organism in a boiling marine water hole close to Maronti Beach, Italy. They used low coverage random shotgun technique to sequence the microorganism's 2.2 million base-pair genome.


The team identified 2,587 protein coding regions and determined that the microorganism is notable for its lack of mismatch-repair mechanisms. These functions for DNA mutation repair are common to organisms from E. coli to homo sapiens but have not yet been found in any of the six archaea that have been sequenced.


As a resullt, the research raises the possibility that these microorganisms may have a "mutation lifestyle," constantly undergoing uncorrected mutations. High-temperature archaea, write the authors, may be "extraordinary examples of organisms that can survive as permanent mutators."


Meanwhile, in the same issue, another team reports the sequencing of Clostridium perfringens, a Gram-positive spore-forming anaerobic bacterium that can cause necrotic enteritis and gas gangrene. The researchers, a Japanese group, say that theirs is the first sequence of a Gram-positive anaerobic pathogen.


The group selected this bacterium as a model organism because it is oxygen-tolerant, quick to grow, and easy to manipulate. The bug, which normally lives in the intestines of humans and animals, can also invade injured tissue and cause toxemia, shock and death. Its genetic neighbors include C. tetani, C. botulinum and C. difficile, which can cause persistent diarrhea and colitis.


The researchers identified 2,660 protein coding regions and 20 new genes related to bacterial virulence. The team included scientists from Hitachi, Japan's University of Tsukuba, Kyushu University, Kitasato University, Advanced Institute of Science, and Technology in Nara, Ikoma, and Human Genome Research Group.

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