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

极端环境中生命最多产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陈代谢类型的极端嗜热古生菌和细菌。这些极端微生物中有许多代表新属(例如，热菌属、甲壳草属)。表现出在高温下完全意想不到的新陈代谢和酶能力。一个恰当的例子是最近分离出的烟曲霉菌，它具有氨化硝酸盐的能力，并能够利用低水平的硫代硫酸盐和氧作为电子受体。这些特征极大地扩展了在海洋、陆地或外星环境的高温下可能发生的微生物变化的类型。没有理由认为这种新型极端微生物的深海来源已经耗尽。我们将结合对嗜热菌的新的浓缩/分离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法(DGGE)对微生物生物多样性进行直观评估、快速鉴定以及对分子和培养的分离株进行平行研究。实地工作和样品采集将在两个产量最高的阿尔文热液喷口地点进行：瓜伊马斯盆地和东太平洋隆起的21多个北端，尽管距离很近，但却具有不同的特点。稀释技术将在我们的文化和分子方法中用于描述种群密度和栖息地范围。我们将把生物多样性方面与沿着选定的氧化还原和温度梯度对嗜热生物的不同代谢类型进行量化联系起来，这些氧化还原和温度梯度通常发生在瓜伊马斯盆地喷口地点，并提供通常分开较长距离的两个生物圈的小规模类似物：(1)最终由光合作用驱动的表层和次表层生物圈的缺氧或缺氧部分，以及(2)可能自主缺氧的深层地下生物圈。由于后者可能含有生物介导的生物地球化学反应，如甲烷和硫化物的形成，以及可能的厌氧金属氧化，它们在外星环境中的潜在作用特别耐人寻味。

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.