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Unearthing terrestrial extreme microbiomes for searching terrestrial-like life in the Solar System

2022; Elsevier BV; Volume: 30; Issue: 11 Linguagem: Inglês

10.1016/j.tim.2022.04.002

1878-4380

Claudia Coleine, Manuel Delgado‐Baquerizo,

Planetary Science and Exploration

All terrestrial environmental niches can be virtually colonized by a wide range of organisms from all three domains of life. Some organisms, including lichenized and free-living fungi, prokaryotes, viruses, and even invertebrates such as tardigrades, not only flourish under such a broad spectrum of parameters on Earth but can also survive the harsh conditions of space. Untangling extreme environments on Earth is crucial for understanding the boundary conditions under which life evolved and adapted on our planet. Studying potential extraterrestrial colonizers through the investigation of extreme terrestrial microbiomes could give clues as to whether (and how) life may persist on other planetary bodies and support the terraformation of planets supporting extreme conditions. The possibility of life elsewhere in the universe has fascinated humankind for ages. To the best of our knowledge, life, as we know it, is limited to planet Earth; yet current investigation suggests that life might be more common than previously thought. In this review, we explore extreme terrestrial analogue environments in the search for some notable examples of extreme organisms, including overlooked microbial groups such as viruses, fungi, and protists, associated with limits of life on Earth. This knowledge is integral to provide the foundational principles needed to predict what sort of Earth-like organisms we might find in the Solar System and beyond, and to understand the future and origins of life on Earth. The possibility of life elsewhere in the universe has fascinated humankind for ages. To the best of our knowledge, life, as we know it, is limited to planet Earth; yet current investigation suggests that life might be more common than previously thought. In this review, we explore extreme terrestrial analogue environments in the search for some notable examples of extreme organisms, including overlooked microbial groups such as viruses, fungi, and protists, associated with limits of life on Earth. This knowledge is integral to provide the foundational principles needed to predict what sort of Earth-like organisms we might find in the Solar System and beyond, and to understand the future and origins of life on Earth. any characteristic, element, molecule, substance, or phenomenon that can be used as evidence for past or present life. A biosignature can provide evidence for living organisms outside the Earth and can be directly or indirectly detected by searching for their unique byproducts. bioregenerative life-support system, an artificial closed ecosystem composed of humans, plants, animals, and microorganisms, which is able to recycle and regenerate oxygen, water, food, and other essential substances needed for human survival, and provide humans with comfortable environments similar to those in the Earth's ecosystem. refers to microorganisms that can gain energy for cell biosynthesis and maintenance from the oxidation of inorganic compounds (= electron donors), in the absence of light. refers to the vast majority of microbial organisms (usually bacteria and archaea) that microbiologists are unable to culture in the laboratory. the process by which a substance absorbs moisture from the atmosphere until it dissolves in the absorbed water and forms a solution. organisms that can tolerate extreme conditions of one or more extreme physical parameters even though they grow optimally under neutral conditions. organisms that require one or more extreme conditions to survive. the concept that microorganisms in rocks can be transferred from one planet to another through interplanetary or interstellar space, by means of rocks ejected through impact processes. This theory postulates that planetary bodies have been seeded with microorganisms which have colonized rocks that were expelled into space from life-harboring planets by asteroid impacts. refers to organisms with a highly melanized cell wall. Melanin is a unique class of pigments, found throughout the biosphere, with a wide variety of functions, structures, and presentations. Melanin types may be classified based on their source (animal, plant, fungal, or bacterial) or chemical and physical features (eumelanin, pheomelanin, neuromelanin, allomelanin, and pyomelanin). Melanins are associated with protection against diverse biotic and abiotic stress factors. Studies on fungi have also shown that melanin can harvest energy from electromagnetic radiation for metabolic use in a process that involves melanin’s electrical properties (referred to as radiosynthesis). the theory that life could be delivered to Earth or any other planet by being carried through space by meteorites, comets, or asteroids. Lithopanspermia proposes that extremophile-type microscopic life could exist in debris blasted into space from planetary collisions with asteroids and comets. Radiopanspermia postulates that organisms might travel through space via radiation pressure from stars. Pseudopanspermia assumes that life originates in interstellar dust clouds. the anion resulting from the dissociation of perchloric acid and its salts upon their dissolution in water. A photochemical process consisting of several reactions involving ozone oxidation, UV radiation, and electrical discharges can naturally form perchlorate. the practice of protecting solar-system bodies from contamination by Earth life and protecting Earth from possible life forms that may be returned from other solar system bodies (National Aeronautics and Space Administration, NASA). environments that are characterized by two or more extreme conditions simultaneously. energy that travels through space and may be able to penetrate various materials. In particular, among major types of radiation, ionizing radiation, depending on the type and length of exposure, damages DNA directly or indirectly, for instance producing reactive oxygen species (ROS) and introducing double-strand breaks in DNA molecules. The exposure to radiation may directly cause DNA mutations, or mutations may be introduced when the cell attempts to repair the DNA damage that could lead to cell death. a discipline that combines principles from engineering, DNA science, and computer science to impart new and improved functions to living organisms. places or spaces on Earth that approximate, to some extent, the geological, environmental, and putative biological conditions of a particular planetary body, under past or present conditions. the amount of unbound water in a sample, namely a thermodynamic measure of water expressed as the vapor pressure of water in a sample divided by vapor pressure of pure water at a given temperature. aw is based on a scale from 0.0 to 1.0. Among the physicochemical parameters that permit or prevent cellular activity, aw is critical; indeed, cells and their macromolecules are reliant on water, and the vast majority of organisms function only when water is abundant.