LEXEN: New Physiological and Phylogenetic Types of Hyperthermophiles at Deep-Sea Hydrothermal Vents

极端环境下的生命最有生产力和最令人兴奋的方面之一是在深海热液喷口发现和描述了新的代谢类型的超嗜热古菌和细菌。这些极端微生物中有许多是新属（如焦菌属、甲烷菌属）。葡萄球菌（Staphylothermus, Archaeoglobus）表现出在高温下完全意想不到的代谢和酶促能力。一个恰当的例子是最近分离出富马氏焦叶菌，它具有氨化硝酸盐和使用硫代硫酸盐以及低水平氧气作为电子受体的能力。这些特征极大地扩展了微生物转化的类型，可以预计在海洋、陆地或地外环境的高温下发生。没有理由认为这种新型极端微生物的深海来源已经枯竭。我们将结合新的富集/分离超嗜热细菌的方法和对其原位发生的分子/系统发育评估。为此，我们将使用变性梯度凝胶电泳（DGGE）对微生物多样性进行视觉评估，快速鉴定和分子和培养分离物的平行研究。实地工作和样品收集将使用DSRV ALVIN在两个最具生产力的热液喷口进行，尽管距离很近，但特征不同：Guaymas盆地和东太平洋隆起的21 ÝN。稀释技术将在我们的文化和分子方法中用于描绘种群密度和栖息地范围。我们将把生物多样性方面与不同代谢类型的超嗜热生物的量化联系起来，这些生物沿着选择的氧化还原和温度梯度（通常发生在瓜伊马斯盆地的火山口），并提供两个通常相隔较大距离的生物圈的小尺度类似物：(1)表面和地下生物圈的氧气或缺氧部分，最终由光合作用驱动；(2)可能自主缺氧的深层地下生物圈。由于后者可能容纳生物体介导生物地球化学反应，如甲烷和硫化物的形成，以及可能的厌氧金属氧化，它们在地外环境中的潜在作用特别有趣。

One of the most productive and exiting aspects of life at extreme environments has been the discovery and description of novel metabolic types of hyperthermophilic archaea and bacteria at deep sea hydrothermal vents. Many of these extremophiles represented new genera (e.g. Pyrodictium, Methanopyrus. Staphylothermus, Archaeoglobus) exhibiting types of metabolism and enzymatic capabilities that were entirely unexpected to occur at high temperatures. A case in point is the recent isolation of Pyrolobus fumarii with its ability to ammonify nitrate and to use thiosulfate as well as oxygen at low levels as electron acceptors. These traits greatly extend the type of microbial transformations that can be projected to occur at high temperatures of oceanic, terrestrial or extraterrestrial environments. There is no reason to assume that this deep sea source of novel extremophiles is exhausted. We will combine new enrichment/isolation approaches for hyperthermophiles with a molecular/phylogenetic assessment of their in situ occurrence. To this end we will use denaturing gradient gel electrophoresis (DGGE) for a visual assessment of microbial biodiversity, rapid identification and parallel studies of molecular and cultured isolates. The field work and sample collecting will be done with the DSRV ALVIN at two most productive and, although in close proximity, characteristically different hydrothermal vent sites: Guaymas Basin and 21 ÝN at the East Pacific Rise. Dilution techniques will be applied to delineate populations densities and habitat ranges in both our cultural and molecular approaches. We will link the biodiversity aspect to quantification of different metabolic types of hyperthermophilic organisms along selected redox and temperature gradients which commonly occur at Guaymas Basin vent sites and offer small scale analogs of two biospheres normally separated by larger distances: (1) the oxic or anoxic parts of the surface and subsurface biosphere, ultimately driven by photosynthesis, and (2) the possibly autonomous anoxic deep subsurface biosphere. Since the latter may hold organisms mediating biogeochemical reactions such as methane and sulfide formation and possibly anaerobic metal oxidations, their potential role in extraterrestrial environments is particularly intriguing.