?生物谷报道：古生菌最早于上世纪70年代末被发现，它们是生命树的3大主要分支之一，另外两种是细菌及真核生物（包括植物和动物）。但是科学家知道最近才从生态角度了解古生菌的生存机制。
??由Georgia大学科学家领导的小组在本周三Toronto举行的美国微生物学会会议上宣布，一种生活在热泉系统的古生菌种类——泉古菌（crenarchaeota）——利用氨作为它们的能量来源。文章的第一作者，UGA的Savannah River生态实验室科学家Chuanlun Zhang表示，这种代谢模式此前从未在其它高温古生菌中发现过。
??Zhang说：“此前我们并不认为氨的氧化是泉古菌中起支配作用的过程，但是现在我们意识到了它的重要性。”Zhang还是海洋学的副教授，他的合作者来自Nevada大学、Montana州立大学、Savannah River国家实验室、哈佛大学等。
??Zhang和同事从美国、中国、俄罗斯的热泉系统中取样，结果发现一种amoA基因广泛存在，微生物用它们将氨和氧结合，然后放出能量。此前其它小组利用DNA技术证明泉古菌能将环境中的氨转化。Zhang认为这一发现显示了泉古菌在极端环境下的生态作用。
??由于这类古生菌生活在类似于原始地球环境的热泉中，因此Zhang表示它们将帮助科学家更好的了解地球生命的早期进化过程。他说：“如果想了解生物和它们的代谢过程的进化，我们就需要同时了解热泉环境和低温环境。因此泉古菌对于我们很重要，它们在这两种环境中都能很好的生存。”
英文原文：
http://www.physorg.com/news99134279.html
Published: 10:17 EST, May 23, 2007
Study reveals function of ubiquitous yet poorly understood microorganisms
Discovered in the late 1970s, archaea are one of the three main branches on the tree of life, with bacteria and eukaryotes such as plants and animals on the other two branches. But scientists are just now gaining a fuller understanding of what archaea do – in an ecological sense – to make a living.
A new study led by University of Georgia researchers and announced on Wednesday at the American Society for Microbiology meeting in Toronto finds that crenarchaeota, one of the most common groups of archaea and a group that includes members that live in hot springs, use ammonia as their energy source. Chuanlun Zhang, lead author of the study and associate research scientist at UGA’s Savannah River Ecology Laboratory, said such a metabolic mode has not been found in any of the other known high-temperature archaea.
"The oxidation of ammonia was not thought to be a dominant process for crenarchaeota, but now we realize how important it is," said Zhang, who is also associate professor of marine sciences. His co-authors include researchers from the University of Nevada Las Vegas, Montana State University, Savannah River National Laboratory, Harvard University and Yunnan University in China.
Zhang and his colleagues (Christopher Bagwell, SRNL; Brian Hedlund, UNLV; Bill Inskeep, MSU; WenJun Li, Yunnan University; Ann Pearson, Harvard; Christopher Romanek and Juergen Wiegel, UGA) sampled extensively from hot springs in the United States, China and Russia for crenarchaeota and found the widespread distribution of the presumed amoA genes, which microorganisms use to combine ammonia with oxygen, releasing useable energy. Previous studies by other teams used a DNA-based forensic ecology approach to suggest crenarchaeota’s role in converting ammonia in mundane environments such as sea water, soil and even waste treatment plants. Zhang said the results of this latest comprehensive study give a picture of the ecological role of crenarchaeota in more extreme environments such as the hot springs.
Because ammonia-oxidizing archaea are associated with a group of microorganisms that thrive in hot spring environments that are thought to resemble early conditions on Earth, Zhang said they may help scientists better understand the earliest stages of evolution on the planet.
"If we want to know how organisms evolved and how their metabolism evolved, we need to understand both the hot springs environment and the low-temperature environment," said Zhang. "Crenarchaeota are special because they thrive in both environments."
Source: University of Georgia
