来自死海的古菌的全基因组揭秘

  古菌与细菌不同，它们多半生活在极端环境，例如高温、高盐、酸性条件等。科学家感兴趣的是，这些古菌为何能抵御这样的极端环境。

  这是一篇发表在Genome Research上的文章。科学家测定了古菌Haloarcula marismortui的全基因组，并把它序列同另一种已测序的嗜盐古菌Halobacterium sp进行比较。研究发现，它们都通过同样的方法对付周围的高盐环境，即有大量的带负电的蛋白。另外，Haloarcula marismortui具有更多的环境反应调控蛋白用来对付多变的环境。另外，在生理代谢上，这两个古菌也有一定的区别。

Abstract: We report the complete sequence of the 4,274,642-bp genome of Haloarcula marismortui, a halophilic archaeal isolate from the Dead Sea. The genome is organized into nine circular replicons of varying G+C compositions ranging from 54% to 62%. Comparison of the genome architectures of Halobacterium sp. NRC-1 and H. marismortui suggests a common ancestor for the two organisms and a genome of significantly reduced size in the former. Both of these halophilic archaea use the same strategy of high surface negative charge of folded proteins as means to circumvent the salting-out phenomenon in a hypersaline cytoplasm. A multitiered annotation approach, including primary sequence similarities, protein family signatures, structure prediction, and a protein function association network, has assigned putative functions for at least 58% of the 4242 predicted proteins, a far larger number than is usually achieved in most newly sequenced microorganisms. Among these assigned functions were genes encoding six opsins, 19 MCP and/or HAMP domain signal transducers, and an unusually large number of environmental response regulators—nearly five times as many as those encoded in Halobacterium sp. NRC-1—suggesting H. marismortui is significantly more physiologically capable of exploiting diverse environments. In comparing the physiologies of the two halophilic archaea, in addition to the expected extensive similarity, we discovered several differences in their metabolic strategies and physiological responses such as distinct pathways for arginine breakdown in each halophile. Finally, as expected from the larger genome, H. marismortui encodes many more functions and seems to have fewer nutritional requirements for survival than does Halobacterium sp. NRC-1.

参考文献：
Nitin S. Baliga1,7, Richard Bonneau1, Marc T. Facciotti1, Min Pan1, Gustavo Glusman1, Eric W. Deutsch1, Paul Shannon1, Yulun Chiu2, Rueyhung Sting Weng3, Rueichi Richie Gan2, Pingliang Hung3, Shailesh V. Date4,6, Edward Marcotte4, Leroy Hood1 and Wailap Victor Ng3,5,7 .
Genome sequence of Haloarcula marismortui: A halophilic archaeon from the Dead Sea.
Genome Research 14:2221-2234, 2004
http://www.genome.org/cgi/doi/10.1101/gr.2700304