[Search for life in deep biospheres]

Area of Science:

• Microbiology
• Astrobiology
• Geochemistry

Context:

• Deep biospheres represent extreme environments on Earth, including deep-sea hydrothermal vents, terrestrial subsurface, and sub-glacial lakes.
• These environments are characterized by the absence of sunlight, anoxic or anaerobic conditions, and unique geochemical gradients.
• They host microbial communities that utilize chemolithoautotrophy, relying on chemical energy sources rather than photosynthesis.

Purpose:

• This review synthesizes microbiological studies from diverse deep biosphere habitats.
• It aims to highlight the unique metabolic strategies and adaptations of life in these dark ecosystems.
• The purpose is to bridge understanding between conventional terrestrial biology and the potential for life beyond Earth (exobiology).

Summary:

• Microbial life in deep biospheres, such as deep-sea hydrothermal vents and the terrestrial subsurface, is primarily driven by chemolithoautotrophy.
• Organisms in these environments utilize chemical energy sources, like sulfide oxidation or anaerobic respiration with various terminal electron acceptors (TEAs).
• Studies of sub-glacial lakes, like Lake Vostok, and deep-sea vents provide insights into life's diversity and potential, informing exobiological exploration.

Impact:

• Findings from deep biosphere research expand our knowledge of Earth's biodiversity and the limits of life.
• Understanding chemolithoautotrophic ecosystems is crucial for identifying potential habitats for life on other celestial bodies, such as Europa.
• Expertise gained from studying these extreme environments enhances capabilities for future exobiological missions and the search for extraterrestrial life.