Thermal tolerance of prokaryote on surface of substrates

限制极端微生物可居住深度的最关键参数之一是温度。已知超嗜热菌的最高生长温度为121℃，但有些微生物生活在底物表面，如热液烟囱，温度超过300℃。因此，假定附着在固体表面的材料可以耐受高温等极端环境。我们通过使用高温井内流体采样器对地热储层进行原位采样来验证这一假设，该采样器可耐受高达300℃的温度。这种钻孔取样器使我们能够在没有剧烈压力变化的情况下，将地热流体就地送入耐压取样室（1250毫升）。此外，所有部件都可以通过高压灭菌器或加热到200摄氏度进行灭菌。我们将采样器应用于位于日本中部长野县Otari村的N18-OT-2地热井（1355米，bbb - 140℃）。该流体富含碳酸氢盐…More （2648 ppm）、Na^+(1752 ppm)和Cl（1048 ppm）。流体氧同位素含量（δ^<18>O<SMOW>=-8.3 permil）表现为氧移，为水岩相互作用的标志。氢同位素含量（^<18>D=-83 peril）相当于当地的大气水。溶解有机碳（DOC）含量低至4.55±0.53mg/L，不足以假设地热储层内部深层生物圈密集。详细的地球化学和同位素模拟表明，该流体是由含钙的浅层温泉水与含CO_2的深层地热流体4:1混合形成的，这些地热流体可能来自第四纪Kazafuki-dake火山附近。值得注意的是，从温泉中获得了一种新的（门级）嗜热化学异养丝状细菌。详细信息将在公布后披露。另一方面，在593米深的井中，附着在方解石鳞上的少量细胞由于数量稀少，无法通过CARD-FISH方法进行培养和鉴定。少

One of the most crucial parameters that limits the habitable depth for extremophiles is temperature. The maximum temperature of growth for hyperthermophile is known to be 121 deg-C but some microbes live on a surface of substrates such as hydrothermal chimneys at temperatures more than 300 deg-C. Therefore, it is presumed that those attached to solid surface may be tolerable to extreme environment such as high temperature.We examined this hypothesis by in-situ sampling from geothermal reservoir using high-temperature, borehole fluid sampler which is tolerant to temperature as high as 300 deg-C. This borehole sampler enables us to get geothermal fluid in-situ to pressure-tight sample chamber (1250 ml) without drastic pressure change. Besides, all the parts can be sterilized either by autoclave or heating up to 200 deg-C.We applied the sampler to a geothermal well N18-OT-2 (1355m,>140 deg-C) that locates in Otari Village, Nagano Prefecture, central Japan. The fluid is rich in bicarbonate … More (2648 ppm), Na^+(1752 ppm) and Cl(1048 ppm). The oxygen isotopic content of the fluid (δ^<18>O<SMOW>=-8.3 permil) shows oxygen shift that is the sign of water rock interaction. The hydrogen isotopic content (^<18>D=-83 permil) is equivalent to local meteoric water. The dissolved organic carbon content (DOC) is as low as 4.55±0.53mg/L which is not high enough to assume intensive deep biosphere within the geothermal reservoir. Detailed geochemical and isotopic modeling indicate that the fluid was formed by 4:1 mixing between shallow, Ca-bearing hot spring water and CO_2 bearing deep geothermal fluid which may come form nearby Quaternary Kazafuki-dake volcano.It is worthy to note that a novel (phylum-level) thermophilic chemo-heterotrophic filamentous bacterium was obtained from the hot spring. Detailed information will be disclosed after publication. On the other hand, small number of cells that attached to the calcite scale of the well at the depth of 593 meters cannot be cultured or identified by CARD-FISH method due to their paucity. Less