The layman’s opinion about the continent of Antarctica can be summed up by the obvious description of ‘cold’. This is understandable since this mystical polar island doesn’t draw attention to itself with lush rainforests, rolling pastures, or ecliptic mountains. If one was to conjure thoughts of Antarctic wildlife, the images would probably be sparse. The birds swim instead of fly and the mammals have flippers instead of legs. Why all the swimming? The water is where most life is possible near the earth’s southern extreme. It is in the water that the microorganisms thrive. Even in the unforgiving conditions, bacteria have developed delicate yet impressive ecosystems that seem almost alien. And that’s exactly what the organism Nostoc sp. is helping to investigate, interplanetary ecosystems.
The organism Nostoc sp. was discovered in 1996 by a team of researchers led Peter Duran of the University of Illinois at Chicago. This cyanobacteria is of the genus Nostoc, while the exact species name has yet to be determined. This bacteria was found in a sample of icy brine extracted from 16 meters below the surface of Lake Vida. Vida is one in a series of Antarctic lakes found in the McMurdo Dry Valley area. The ice layer is in total 19 meters thick, floating on a hypersaline sea that is seven times saltier than that of the standard ocean variety. It precisely this super-salinity that permits the water to be liquid at -10 degrees Celsius: the numerous salt ions lower the water’s eutectic melting temperature and keep the water in its liquid phase.
Since no light can pass through 62 feet of sold ice and gravel, it is presently a mystery as to how a photosynthetic bacterium survives in the absence of light. It can only be assumed that it is capable of fixing other compounds in the environment to obtain energy or lives in symbiosis with indigenous organisms. Since the Nostoc genus is known to produce nitrogen fixing bodies, or heterocysts, inorganic nitrogen may provide the driving force for biosynthesis.
No bacteria were taken directly from aqueous portion of Lake Vida, rather the frozen brine layer directly above it. Since the equipment the research team was implementing was strictly for ice sampling, they did not want to contaminate the liquid portion with the improper instruments. At the McMurdo field lab, the ice samples were slowly thawed to reveal viable organisms. Since life prospers underneath the ice layer rather than above it, the fossil record of the lake is inverted. As one moves up a cross section of Antarctic lake ice, the frozen organisms are progressively more and more ancient. Some of the Lake Vida samples date back more than 2,800 years, which gives some insight about the reproductive viability about these extreme microbial ecosystems. It implies that the bacterial communities are well established, fully adapted to their harsh living conditions. The researchers plan to directly investigate the ecosystem of Nostoc Sp. (i.e. water samples) as soon as possible.
What makes Nostoc sp interesting is not so much a particular behavior but its ability to live in such an extreme environment. The fact that this species can viably reproduce and thrive in sub-freezing temperatures has numerous potential applications. First off, DNA from the nearly 3,000 year old bacteria will be compared to that of the current community. The results of such comparisons could provide great insight as to how DNA changes over time, both in terms of expression and composition. The Lake Vida ice layer could serve as a genealogical model for the DNA of many more organisms than just Antarctic bacteria. In addition to the large, sweeping genetic implications of the discovery of Nostoc sp, some finer benefits should surface. These bacteria may contain specific enzymes that prevent the formation of ice or that allow a living organism to undergo multiple freezing and thawing cycles without harm. On obvious application of this attribute is the creation of a non-toxic antifreeze, but more suitable uses will become apparent as study progresses.
Since the extreme living conditions of Nostoc sp are thought to closely resemble those of certain planetary bodies, the mere existence of this organism serves as enough evidence for some scientists to fervently support the idea of extraterrestrial life. The scientists do not necessarily assume sentient, bipedal organisms roam the surfaces of these potential sites, but rather pose convincing arguments towards the existence of microbial life. These cases are based upon the similarities in temperature, oxygen content, and water composition that both alien and Antarctic sites share. Mars in particular serves a prime site for such anaerobic bacteria. It accepted by most that Mars at one time had terrestrial, aqueous water. Assuming that some water remains, there could possibly be pockets of super-saline solution that sustain communities that mirror those found in Lake Vida. Even if no living organisms were collected, the finding of irrefutable evidence of interplanetary life would be ground breaking. While Nostoc sp is a far stretch from nostalgic science fiction, the grandeur and fascination with such a curiosity remain untainted. So the question is posed: Does the viability of an organism like Nostoc sp, which lives in a possibly Martian environment, justify a manned mission to the Red Planet? This finding could persuade any fence-walkers to recommit their affiliation (and their tax dollars). Do cousins of Nostoc sp float through a subterranean Martian sea? Humanity may find out soon.
Nostoc sp. is a true extremophile that sheds new insight on the adaptability of life. In a nutritionally stretched world devoid of light, Nostoc Sp. go about their lives oblivious to their harsh living conditions. The bacteria’s nutritional flexibility and specialized enzyme toolkit exemplify how life can adjust to compensate for most any set of environmental conditions imaginable.
Bibliography
“Researchers find 3,000-Year-Old Microbes in Mars-like Antarctic Environment”. Internet. www.scienceblog.com/community/article603.html. February 9, 2004.
Nylen, Thomas. “The Lost World of Lake Vida”. Internet. www.campbellsci.co.uk/Applications/lake_vida_background.PDF
February 9, 2004.Priscu, John C. Perennial Arctic Lake Ice: A refuge for Cyanobacteria in an Extreme Environment. http://www.homepage.montana.edu/~lkbonney/DOCS/Publications/Ancient%20Ice%20Paper.pdf
February 9, 2004.*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.
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