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  • 极端主义者

    Extremophiles
    ::极端主义者

    Extremophiles are organisms that live in habitats that seem extreme to humans. The ability of organisms on Earth to  live in a wide range of environments is the secret to the survival of life on this planet and extremophiles help us to understand the limits to life. On the early Earth, the large swings in climate  would have cycled between  hot and freezing conditions. Before  microbes invented photosynthesis,  life  adapted to take advantage of many different metabolic pathways. There is evidence in the geologic record that oxygen levels in the atmosphere fluctuated wildly before a precipitous rise 2.4 Gya.  Through every mass extinction, there were some niches of life that survived. Even o ur flammable, oxygen-rich atmosphere constitutes an extreme environment.
    ::极端嗜血动物是生活在人类看来极端极端的生境中的生物体。地球上生物体在广泛环境中生存的能力是地球上生命和极端嗜血动物生存的秘密,有助于我们了解生命的极限。在早期的地球上,气候的大规模摇动本会在热和冷的状态之间循环。在微生物发明光合作用之前,生命经过调整以利用许多不同的代谢途径。在地质记录中,有证据表明大气中的氧水平在急速上升之前急剧波动。在每次大规模灭绝中,都存在一些生存下来的生命环境。甚至我们的可燃、含氧大气也构成了一种极端的环境。

    Being "extreme" is in the eye of the beholder. Most of the organisms that humans identify as extremophiles are small prokaryotes in the Archaea or Bacteria domain. They are known to survive in a wide range of extraordinary environments.
    ::人类认定为极端生物的多数生物都是Archaea或细菌领域的小原虫。已知它们生存在各种不同寻常的环境中。

     (temperature-loving organisms)  live  in high temperature environments, some at temperatures of 235°F (113 °C ).  Vast hydrothermal environments can be found on land surfaces and the deep seafloor. High temperatures are challenging for life because the energy causes proteins to denature, or unfold.  Chemical reactions proceed more quickly, and temperatures above 100 ∘ C can denature nucleic acids, causing  DNA  to lose  its helical shape or break apart the structure of biomolecules. The fluidity and permeability of cell membranes are affected by heat. High temperatures  decrease the solubility of carbon dioxide and oxygen in water, a problem for aquatic aerobic life. Thermophiles have metabolisms that take advantage of the higher chemical reactivity  enabled by  high temperatures.  They  make use of   special temperature-resistant proteins and protective mechanisms for shielding DNA. Thermophile coping mechanisms include an altered ratio of saturated hydrocarbons in cell membranes.
    ::高温对生命具有挑战性,因为能量导致蛋白质变硬或变形。 化学反应更快地进行,超过100°C的温度可以使核酸变硬,导致DNA失去其热形状或分裂生物分子结构。细胞膜的流动性和渗透性受到热量的影响。高温降低了水中的二氧化碳和氧的溶性,这是水生有氧生命的一个问题。热剂具有新陈代谢作用,利用高温产生的较高化学再活性。它们利用特殊的耐温度蛋白和防护机制保护DNA。热剂的应对机制包括细胞膜中饱和碳氢化合物的改变比率。

    The young Earth, with a tremendous amount of internal energy from accretion and differentiation, may have harbored many hot springs and ocean floor hydrothermal vents. Young Earth would have been a paradise for thermophiles, and the archea and bacteria that are most deeply rooted in the phylogenetic tree of life are thermophiles.  The range of metabolisms for thermophiles may be the result of the diversity of chemistry at deep sea hydrothermal vents. 
    ::年轻地球拥有巨大的内分泌能量,它可能拥有许多温泉和洋底热液喷口。 年轻地球本来会是热病的天堂,而植根于生命的植物树上的考古和细菌则是热病。 热病的新陈代谢范围可能是深海热液喷口化学多样性的结果。

     

     

     

    The Great Prismatic Spring of Yellowstone National Park. This hot spring provides a fascinating study of thermophiles. The rings of different colors represent different thermophiles that survive best at different temperatures. The closer to the water, which reaches a balmy 92F, the greater the temperature these microbes can withstand.
    ::黄石公园的伟大原始之春。 这个温泉提供了对热病的迷人的研究。 不同颜色的环代表不同温度下最能存活的不同的热病。 离水越近,温度越低,这些微生物能承受的温度就越大。

     

    Psychrophiles  are organisms that can withstand extreme cold. They are found in liquid brine inclusions in ice cores, or living under rocks in the extreme deserts of the world where temperatures can reach below -60 ° F  (-50 °C ) . This class of extremophiles includes bacteria and eukaryotes. Cells must be resilient to freezing, which can form ice shards that would pierce and destroy  ordinary cells. One defense of a psychrophile is to lower the freezing point with solutes in cytoplasm that essentially act as an antifreeze. To increase fluidity of cell membranes, psychrophiles have evolved a different ratio of unsaturated to saturated fats. At cold temperatures, proteins are more rigid,  so enzymes are used  to  lower the activation energy for biochemical reactions.  
    ::蛋白质是能够承受极端寒冷的有机体。它们存在于冰芯中的液体盐溶液中,或生活在世界极端沙漠中的岩石下,那里的温度可能低于-60摄氏度(-50摄氏度),这种极端生物包括细菌和尤卡利奥特。细胞必须具有耐寒性,能够形成冰块,从而穿透和摧毁普通细胞。精神病病菌的一种防御手段是降低冰点的溶液含量,将溶液溶液放在细胞中,这基本上是一种抗冻物。为了增加细胞膜的流动性,精神病学家已经形成了一种不饱和与饱和脂肪的不同比例。在寒冷的温度下,蛋白质更加僵硬,因此酶被用来降低生物化学反应的活性能量。

    and alkaliphiles  thrive in environments with very low or high pH, respectively. Intense acids and bases are capable of breaking down organic chemicals and denaturing proteins. Acidophiles have been found in conditions as acidic as battery acid. They have been able to adapt mechanisms for keeping the acid out so that the cell cytoplasm can have a neutral pH. 
    ::碱性生物在pH值非常低或很高的环境中蓬勃发展。 强烈的酸和碱性物质能够打破有机化学物和衰减蛋白质。 在酸性与电池酸一样的条件下发现了酸性物质。 它们能够调整机制,保持酸性,以便细胞细胞的细胞细胞顶层能够有一个中性pH值。

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    Acidophiles found in standing water with the acidity of battery acid.
    ::静态水中发现的酸性电池酸酸的酸性物。

    Life has even been found next to nuclear waste storage sites in the presence of enough radiation to grant super powers. Radiation can be very damaging to DNA and cause cancerous cells or  tumors. These radioresistant organisms have evolved mechanisms to protect their DNA even in the presence of over 1000 times the radiation a typical organism can withstand.
    ::在核废料储存场附近甚至发现了生命,有足够的辐射来赋予超强力量。 辐射可能对DNA造成极大伤害,并导致癌症细胞或肿瘤。 这些抗辐射生物已经发展出保护其DNA的机制,即使存在超过典型生物能承受的1000倍的辐射。

    There  also still exist  anaerobes that do not require oxygen and live deep underground. There are barophiles or piezophiles that thrive in high-pressure environments. Halophiles can only survive in an environment with high concentrations of salt, an environment  that would dehydrate most other organisms. Zerophiles require very little water and are found in the soil of the world's largest deserts.
    ::此外,还有不需要氧气和在地下深处生存的厌食动物,还有在高压环境中生长的野兽或肉毒杆菌,只能够在盐含量高的环境中生存,这种环境中大多数其他生物都会脱水,零生物需要的水很少,并且在世界最大的沙漠的土壤中被发现。

    The discovery of extremophiles has greatly expanded our understanding of the range  of environments that can host life. They are a great boon to astrobiology both in demonstrating the wide variety of life that is possible, and by expanding the definition of what is "habitable." 
    ::极端嗜血嗜血症的发现极大地扩大了我们对可以容纳生命的环境范围的理解。 它们对于天体生物学来说是巨大的好处,既展示了各种可能的生活,又扩大了“可居住”的定义。

    Tardigrades
    ::塔尔底职等

    , or water bears, are not technically extremophiles but are nevertheless extreme in their own right  as well as strangely adorable. They are a type of micro-animal, only 0.5mm in length on average, with eight-legs, typically found in water, and among the most resilient creatures known. They are different from extremophiles, which are adapted to live in terrifyingly harsh conditions, because they do best in average conditions.  However, they are capable of on this world, including low pressure environments  in space.
    ::水熊(水熊)不是技术上的极端嗜血动物,但其本身是极端的,而且奇怪的是可爱的。它们是一种微动物,平均只有0.5毫米长,八条腿,通常在水中发现,也是最有弹性的生物之一。它们不同于极端嗜血动物,它们适应于在可怕的恶劣条件下生活,因为它们在平均条件下做得最好。然而,它们能够在世界上生存,包括空间低压环境。

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    Tardigrades are hearty creatures that can survive in almost any environment. They may now be scattered across the lunar surface after an Israeli rocket crashed on the moon.
    ::塔迪格勒斯是几乎在任何环境中都能生存下来的心地生物,在以色列火箭在月球上坠毁后,它们现在可能分散在月球表面。

    In 2007, samples of tardigrades were taken into low Earth orbit and exposed to the vacuum and radiation of space for 10 days. After the reanimation of the tardigrades back on Earth, most of the tardigrades began living  as normal after 30 minutes (though most of the sample did suffer later health effects). Their incredible resilience allowed water bears to survive through five great extinction events on Earth. Their capability to survive in space gives new life to the theory of panspermia. Though not technically extremophiles, tardigrades certainly  win a prize for resilience.
    ::2007年,在低地球轨道上采集了缓冲层样本,并暴露在真空和空间辐射中达10天之久。在地球的缓冲层恢复了活力后,大部分缓冲层在30分钟后开始正常生活(尽管大部分样本的确受到后来的健康影响 ) 。 它们令人难以置信的抗御力让水熊得以通过地球上的五大灭绝事件生存下来。它们在太空生存的能力为全面性理论注入了新的生命力。 尽管从技术上讲,缓冲层在技术上不是极端细胞,但确实赢得了抗御力奖。

    In April 2019, an Israeli  spacecraft called Beresheet almost made it to the moon. The privately funded mission was the first stage of a privately funded project to transfer DNA to the moon to  build a repository for rebuilding life in the event of catastrophic mass extinction. Among the passengers on the spacecraft: dehydrated tardigrades. It is unlikely that these creatures could survive on the moon without liquid water.
    ::2019年4月,以色列一艘名为贝雷谢克的航天器几乎到达月球。 私人资助的飞行任务是私人资助的一个项目的第一阶段,该项目旨在将DNA转移到月球,以建立一个在灾难性大规模灭绝的情况下重建生命的存放处。 在航天器上的乘客中:脱水焦油。 这些生物不可能在没有液体水的情况下在月球上生存。

    Got Water?
    ::有水吗?

    Extremophiles  occupy  the entire range of environments it is possible to have on Earth . However, neither tardigrades nor any extremophile found yet can survive  in the absence of water. Water is thought to be essential to life both because where there is life there is water and where there is water there is life. W ater possess many unique  chemical properties that make it conducive to both life and the organic reactions that govern it.
    ::极端主义分子占据着地球上所有的环境,然而,如果没有水,既无法生存,也无法生存,因为水对生命至关重要,因为那里有水,也存在水。水拥有许多独特的化学特性,既有利于生命,也有利于支配生命的有机反应。

    Water makes up the most of most living systems. The average organism is 70% or more water by weight. Recall that water, or H 2 O, consists of one oxygen molecule and two hydrogen molecules. As mentioned before, oxygen is particularly good at attracting electrons. Even within a molecule of water, the electrons preferentially spend time  closer to the oxygen molecule than to  the hydrogen atoms. Because electrons carry a negative charge, the result is that the oxygen molecule is slightly negative while the hydrogen atoms are left with a slightly positive residual charge.
    ::水构成大多数生命系统。 平均生物量按重量计算为70%或70%以上。 回顾水或H2O由一个氧分子和两个氢分子组成。 如前所述, 氧在吸引电子方面特别好。 即使在水分子中, 电子也比氢原子更倾向于使用更接近氧分子的时间。 由于电子带有负电荷, 结果是氧分子略为阴性, 而氢原子的剩余电荷则略为正值。

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    The water molecule is slightly polar.
    ::水分子略微极化。

    This charge differential across the water molecules  makes and consequently useful for organic chemistry in several ways. The different charges help group nonpolar molecules together and create effects like self-assembling phospholipid structures. Proteins are also folded with the help of water  when amino acids with nonpolar side chains are naturally folded inside more water-friendly side chains.
    ::这种水分子的电荷差异以几种方式产生并因此对有机化学有用。 不同的电荷有助于将非极分子组合在一起,并产生自组装磷叶素结构等效应。 当氨基酸与非极性侧链自然叠放在更有利于水的侧链条中时,蛋白质也会与水相叠。

    Because of its polarity, water has a strong bond to neighboring water molecules. Water molecules can form hydrogen bonds with one another. These bonds help water to remain liquid over a greater range of temperature. Water provides a safe, stable environment to nurture the  complex reactions required by life.
    ::由于水的两极性,水与相邻的水分子有着紧密的联系。 水分子可以形成氢联结。 水分子可以形成氢联结。 这些联结有助于水在更大范围的温度下保持液态。 水提供了一个安全稳定的环境来培育生命所需的复杂反应。

    The difference in charge also allows water to more easily  pull compounds apart, making it easier for chemicals (like the salt  crystal in the   below) to dissolve in water. This has earned water the moniker "the universal solvent."  Once in the water, chemicals are free to move around and interact with other chemicals. 
    ::电荷差异还使得水更容易分离化合物,使化学物质(如下面的盐晶)更容易溶解于水中。这为水创造了“通用溶剂 ” 。 一旦进入水中,化学物质就可以自由移动并与其他化学物质互动。

     

     

    A crystal of table salt (NaCl) dissolving in water. The table salt is easily dissolved into negatively charged chlorine ions (green) and the positively charged sodium ions (yellow) in water where the ions are stabilized through interacting with the differently charged ends of water. What section of the water molecule preferentially faces the sodium atom and which end preferentially faces the chlorine atom? Recall that it is opposite charges that attract.
    ::在水中溶解的桌盐晶体(NaCl)中,桌盐很容易溶解成负充电氯离子(绿色)和正充电的水中离子(黄)钠(黄),因为离子通过与不同充电端的水相互作用稳定。水分子的哪一部分偏好面对钠原子,而哪个部分则优先面对氯原子?提醒注意的是相反的电荷会吸引人。

    When water freezes into ice, the positively-charged hydrogen atoms align with the negatively-charged oxygen atoms, forming an organized lattice (  below). In this highly-organized configuration, the molecules in ice  are  more widely spaced than molecules in water, resulting in a lower density that allows ice to float on top of water. This property carries many benefits for biology as ice can therefore serve as a protective barrier for the water underneath. It is capable of blocking out potentially damaging radiation and cooling water to stabilize certain compounds.
    ::当水冻结在冰中时,正充电氢原子与负充电氧原子相匹配,形成一个有条不紊的阵列(下面)。在这种高度有组织的结构中,冰中的分子比水中的分子空间更广,导致密度较低,使冰能漂浮在水面上。这种特性对生物学有许多好处,因为冰因此可以作为底部水的防护屏障。它能够阻断具有潜在破坏性的辐射和冷却水以稳定某些化合物。

     

     

    The 3D crystal lattice formed by water molecules when frozen into ice. Oxygen atoms are shown in red while hydrogen atoms are white. Hydrogen bonds are displayed as three light blue stripes. This configuration makes for a regular spacing that renders ice less dense than water. This crystal lattice is also what makes snowflakes such a unique and timeless beauty.
    ::3D 晶体层由水分子在冰冻时形成。 氧原子以红色显示, 氢原子以白色显示。 氢结层以三个浅蓝色条状显示。 这种配置使冰的密度低于水的正常间距变小。 这个晶体层也使雪花如此独特和永恒的美丽。

       Icy Worlds
    ::冰冰世界

    In recent years, the search for life in the solar system has expanded beyond Mars to also  include some surprising places. Chief among them is a moon of Jupiter named Europa. Pictures of Europa reveal an exceedingly smooth surface with only cracks, no craters. For this reason, it is believed that Europa may be an ocean world covered by a layer of ice capable of recovering from impacts. Because of the close association of water to life, Europa is gaining popularity as the next target of a NASA mission to discover extraterrestrial life. As the wettest known world in the Solar System, Europa may be teeming with life just under the surface.
    ::近年来,太阳系对生命的探索已扩展到火星以外,还包括一些令人惊讶的地方。其中最主要的是木星,名为欧罗巴。欧罗巴的图片显示表面极平滑,只有裂缝,没有弹坑。因此,人们相信欧罗巴可能是一个海洋世界,由一层冰层覆盖,能够从撞击中恢复过来。由于水与生命的密切联系,欧罗巴越来越受欢迎,成为美国航天局探索外星生命任务的下一个目标。作为太阳系中已知的潮湿世界,欧罗巴可能与地表下的生命相伴而生。

     

     

    A true-color image of the surface of Europa. Areas with a darker color are thought to indicate areas where the surface ice contains more minerals. How does the number of craters on Europa compare to the number of craters on our Moon?
    ::Europa 表面真实颜色的图像。 暗色区域被认为是指表层冰中含有更多矿物质的区域。 与我们月球上的弹坑数量相比, Europa 上的弹坑数量如何 ?

     

    Saturn's moon Enceladus is also making a splash. Back in 2005, the Cassini spacecraft in orbit around Saturn discovered water geysers  at the south pole of Enceladaus. I t is thought  that water from these geysers freezes into ice upon being released from Enceladus and adds to the ice in Saturn's rings, making them shinier. With a confirmed source of water under an icy surface, the story of Enceladus  became even  more exciting after the Cassini spacecraft maneuvered through one of the geysers on Enceladus. Cassini was able to detect high levels of hydrogen gas being expelled with the geyser. Though more information is  needed, this preliminary finding suggests that geysers on Enceladus may  resemble the deep-sea vents on Earth, thought to be the sites for the genesis of life.
    ::土星的月亮土星土耳多斯也正在喷洒。 2005年,在土星环绕轨道的卡西尼航天器在恩塞拉达斯的南边发现了水滤水器。人们认为,这些喷泉的水在从土耳拉杜斯释放出来后冻结在冰中,并增加了土星环的冰层,使土星环的冰层更加亮亮。随着冰层表面下的一个经证实的水源,土卫斯的土卫斯的故事在卡西尼航天器在恩塞拉杜斯岛的一个地缘上航行后变得更加令人兴奋。卡西尼能够探测到高水平的氢气会与喷出。尽管需要更多的信息,但这一初步发现表明,土卫六的喷泉可能类似于地球上的深海喷口,被认为是生命起源的地点。

     

     

    An artist's rendition of the Cassini spacecraft flying through the plumes of Enceladus.
    ::一位艺术家将卡西尼号太空船引渡 飞过土卫二的羽流

    The helpful properties of both water and ice are expanding the possibilities of what is deemed habitable. It might turn out that alien neighbors are closer than we thought.
    ::水和冰的有益特性正在扩大被视为可居住的事物的可能性。 可能会发现外来邻国比我们想象的更接近。

    Water is so essential for life as we know it that the search is on for sources and signs of water in space. Though water might not definitely point to life , it is hard to imagine  life without water.
    ::水对于生命如此重要,因为我们知道,寻找空间水源和水迹象的工作正在进行中。 尽管水不一定指向生命,但很难想象没有水的生活。