Are any microbes hardy enough to survive in outer space?
Microbes are versatile. They possess the series of enzymatic machinery to bring out the biochemical changes inside as well outside the cell, thereby impacting the environment in which they are present. Microbes have the capability to adapt to any kind of adverse conditions and they thrive for the survival by exploiting their fullest genomic and biochemical potential. And after all, when there is a question of survival of any life, the fittest one wins!
Life can thrive in some of the most extreme environments on the planet. Microbes flourish inside hot geothermal vents, beneath the frigid ice covering Antarctica and under immense pressures at the bottom of the ocean.
Are any microbes sturdy enough to survive in outer space? Through the experiments conducted by the space scientists, it was found that many microbes survive and even thrive in a space-vessel environment. Most do even worse when exposed to some of the actual conditions of outer space, either in the laboratory or in space.
Arriving in space without any protection, microorganisms are confronted with an extremely hostile environment, characterized by an intense radiation field of galactic and solar origin, high vacuum, extreme temperatures, and microgravity. The vast, cold, and radiation-filled conditions of outer space present an environmental challenge for any form of life. Earth’s biosphere has evolved for more than 3 billion years, shielded by the protective blanket of the atmosphere protecting terrestrial life from the hostile environment of outer space. Within the last 50 years, space technology has provided tools for transporting terrestrial life beyond this protective shield in order to study in situ responses to selected conditions of space.
Of all the organisms tested, only some lichens, Rhizocarpon geographicum and Xanthoria elegans, were fully viable after two weeks in outer space, with its radiation, vacuum, temperature extremes and low gravity. The most lethal factor, found was the high level of solar ultraviolet radiation found beyond the ozone layer. However, if spores of Bacillus subtilis, a common bacterium, were shielded against the radiation, they did survive in space for up to six years, especially if they were embedded in clay or in artificial meteorites made of meteorite powder. These findings support the possibility of interplanetary transfer of microorganisms within meteorites. The question of microbe survival has been of interest to scientists since the early days of space exploration, out of concern both that extraterrestrial microbes might be accidentally brought back to Earth and that Earthly ones might contaminate space.
For these organisms to survive and function, so must the enzymes that enable them to live and grow. The research has been focused on what allows particular enzymes to function under extreme environmental conditions. Enzymes are proteins that catalyze the critical biochemical reactions in an organism, and for it to work, its molecular structure has to be stable and flexible.
Higher temperatures would loosen the atomic interactions in an enzyme, making it less stable but more flexible. High pressures would compress the enzyme and force it to become more rigid, making it more stable but less flexible. So for an enzyme under extreme conditions to function, it must adapt to have the right level of stability and flexibility. An enzyme adapted to high pressures, for example, might be more flexible than if it were adapted to normal pressures.
Researchers used computers to simulate the behavior of an enzyme at the molecular level, under various pressures and temperatures. They focused on a well-studied enzyme called dihydrofolate reductase, which is found in the familiar E. coli, a bacterium that lives under normal conditions, called a mesophile. They also studied a high-pressure version of the enzyme found in M. profunda, a microbe found at the bottom of the Atlantic, making it both a piezophilic (pressure-loving) organism as well as a psychrophilic (cold-loving) organism. Understanding how these so-called extremophiles thrive helps scientists gauge under what conditions life can exist – whether it’s in the ocean, deep underground, or even outer space. These kinds of studies could even help researchers engineer proteins from mesophilic organisms to work in extreme conditions. Scientists can change the DNA sequence or the amino acids of a mesophilic protein and make it function under high pressure, low or high temperatures, just like those extremophiles. This could lead to industrial applications in making biofuels and other chemicals that require extreme conditions for optimal production. Knowing the limits of microbial life could also be useful for sterilizing and preserving food by high-pressure processing. The search for signatures of life forms on another planet or moon in our solar system is one of the most prominent goals of space expeditions. Our neighbor planet Mars and Jupiter’s moon Europa are considered key targets for the search for life beyond Earth. By analogy, with terrestrial extremophilic microbial communities, e.g., those thriving in arid, cold, salty environments and/or those exposed to intense UV radiation, additional potential extraterrestrial habitats may be identified. Also, sulfur-rich subsurface areas for studying chemo-autotrophic communities, rocks for endolithic communities, permafrost regions, hydrothermal vents, and soil or evaporite crusts are all of interest. Field studies with microbial communities in those extreme environments as well as microbiological studies under simulated planetary environments—in space as well as in the laboratory—will provide valuable information for preparing the correct “search-for life” experiments on missions to those solar system bodies. Another important role of microbiologists in space exploration concerns the planetary protection initiative. Spacecraft can unintentionally introduce terrestrial microorganisms to the planet or moon of concern. This may destroy the opportunity to examine these bodies in their pristine condition. To prevent the undesirable introduction and possible proliferation of terrestrial microorganisms on the target body, the concept of planetary protection has been introduced. The planetary protection guidelines require cleaning and, in specific cases, sterilization of the spacecraft or components to avoid contamination with terrestrial organisms.
Microbes are versatile and smart too. It’s microbiologists’ most important role to exploit them in a right way and of course to control them at the right time before it is too late.