Recent progress in extremophile biology, exploration of planetary bodies in the solar system, and the detection and characterization of extrasolar planets are leading to new insights in the field of astrobiology and possible distribution of life in the universe. Among the many extremophiles on Earth, the halophilic Archaea (Haloarchaea) are especially attractive models for astrobiology, being evolutionarily ancient and physiologically versatile, potentially surviving in a variety of planetary environments and with relevance for in situ life detection. Haloarchaea are polyextremophilic with tolerance of saturating salinity, anaerobic conditions, high levels of ultraviolet and ionizing radiation, subzero temperatures, desiccation, and toxic ions. Haloarchaea survive launches into Earth’s stratosphere encountering conditions similar to those found on the surface of Mars. Studies of their unique proteins are revealing mechanisms permitting activity and function in high ionic strength, perchlorates, and subzero temperatures. Haloarchaea also produce spectacular blooms visible from space due to synthesis of red–orange isoprenoid carotenoids used for photoprotection and photorepair processes and purple retinal chromoproteins for phototrophy and phototaxis. Remote sensing using visible and infrared spectroscopy has shown that haloarchaeal pigments exhibit both a discernable peak of absorption and a reflective “green edge”. Since the pigments produce remotely detectable features, they may influence the spectrum from an inhabited exoplanet imaged by a future large space-based telescope. In this review, we focus primarily on studies of two Haloarchaea, Halobacterium sp. NRC-1 and Halorubrum lacusprofundi.

中文翻译：

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极端生物学的天体生物学模型：卤古细菌生存策略和色素用于遥感。

极端微生物的最新进展，对太阳系行星体的探索以及太阳系外行星的检测和表征，正在导致在天体生物学和宇宙中可能的生命分布领域的新见解。在地球上的许多极端微生物中，嗜盐古生菌（Haloarchaea）特别是引人注目的天体生物学模型，具有古老的进化和生理学的用途，可以在各种行星环境中生存并与原位生命检测相关。Haloarchaea具有多极嗜热性，能够耐受饱和盐度，厌氧条件，高水平的紫外线和电离辐射，零度以下的温度，干燥和有毒离子。Haloarchaea幸存下来进入地球的平流层，遇到的条件类似于在火星表面上发现的条件。对它们独特蛋白质的研究揭示了在高离子强度，高氯酸盐和零度以下温度下具有活性和功能的机制。由于用于光保护和光修复过程的红橙色类异戊二烯类胡萝卜素和用于光养性和趋光性的紫色视网膜色蛋白的合成，Haloarchaea还产生了从太空可见的壮观花朵。使用可见光谱和红外光谱的遥感显示，卤代古兰色颜料既显示出可识别的吸收峰，又显示出反射性的“绿色边缘”。由于这些颜料具有可远程检测的特征，因此它们可能会影响由未来大型天基望远镜成像的居住系外行星的光谱。盐杆菌属 NRC-1和Halorubrum lacusprofundi。