|
|
|
Cosmology: The invincible beings
They are tiny and tough, and true to their name, they exist in extreme surroundings. They have been around since time immemorial and are probably the oldest living creatures to inhabit our planet and also elsewhere where life may exist in the universe.
A subject for close study by scientists and astrobiologists around the world, extremophiles can live and even flourish in extreme conditions which humans simply cannot withstand. The first of extremophiles were found in the Yellowstone National Park in America in the late 1960s.
Known as “Thermophile”, it thrived in extremely hot water temperatures and was appropriately nicknamed “Thermus Aquaticus” or “warm bath dweller”. These tiny resilient creatures not only managed to bear but also survive in 160 degrees Fahrenheit. For better understanding, think of the hot bath water that scalds our hand if we let it run for long. However, the temperature of our scalding water will not be more than 140 degrees Fahrenheit.
Interestingly, Thermophiles still have it pretty easy when compared to another of its kind, the “Hyperthermophile”. This tiny critter can have a leisurely swim in water as hot as 235 degrees Fahrenheit. Not only is this above boiling point but the temperature is capable of damaging many a tough upholstery.
Psychrophiles, another type of extremophiles can live comfortably below freezing temperature, while acidophiles and alkaliphiles live in extreme acidic and basic solutions, Halophiles find lodging in heavy-duty brines suitable. Then there are some that have no problems living in crushing high pressures or dusty dryness. There are some who do not get hassled by nuclear radiation and some who can even find a good night’s sleep in aviation fuel.
The interesting question here is how do they do it? How do these microbial creatures which most of them are, put up barriers and defences against such odds? Experts feel there are two plans that might be put to work here: either they put up a strong barrier against these harsh elements or change their metabolism. For example, Halophiles increase the concentration of salts in their bodies to survive in a heavy saline environment. With the high amount of salt in and out of their bodies, the level of salts will remain intact and will not drain these organisms of water. Psychrophiles, the dwellers of the cold regions are equipped with special kinds of proteins to survive the cold. These proteins act as antifreeze and thus prevent the cells from congealing, expanding or breaking. In addition, other enzymes and proteins make sure that the chemistry goes on functioning even when the temperatures go down to single digits.
Furthermore, these radiation-busting beings have the most sophisticated tool-kit and first aid box. The DNA repair system inside these creatures sits within its tiny cell walls and easily recovers from extreme exposure to high-energy radiation by fixing the damage without much ado. Experts feel that these microbes would be much useful in protection against skin cancer and even in cleaning up radioactive spills.
Scientists assume that the extreme life forms that we find on Earth probably thrive elsewhere in the solar system as well. In other words, Extremophiles under Europa's frozen seas or under the cold sands of Mars, bombarded by ultraviolet rays, would find it a most comfortable habitat. It is also possible that extremophiles are our oldest ancestors and have the ability to survive in unthinkable conditions and are thus thriving in another solar system somewhere — a place where there is still chaos due to young star formation and where things are just about to settle down.
In the 1970s, studies were carried out that revealed that Thermophiles are probably the oldest life forms we know. This notion also agrees with the fact that in the beginning, when conditions on earth were violent and the surface was pock marked with steaming, sizzling fiery liquids, Thermophiles, were possibly hanging in there to pave the way for future species.
Though this scenario is very viable, it is not hundred percent true. Perhaps life did arise in more moderate and friendly conditions. But then, scientists say that a rock from outer space came and blew out the candle on all life forms on the planet. All of it except the ones surviving in the hydrothermal vents under the seas. It is now an intriguing study for astrobiologists to find out whether these ancient, tiny creatures represent biology in other planets as well.
In the unwelcome and harsh waters on Mono Lake in northern California, a new species of bacteria seems to be thriving without oxygen. The conditions around Mono Lake resemble many of the places on the Red Planet, where scientists presume there might be life. Moreover, what makes our prospective Martians green is the fact that the dye that was used in the laboratory to sort the live bacteria from the dead made the creatures appear green in the image. They looked like tiny, miniature corkscrews spinning in the highly alkaline water that they are used to.
Though the discussion of any life form on Mars is purely speculative at the moment, creatures on Earth seem to be rearing their heads all the time from conditions and environs absolutely unbearable to human understanding. They are supposed to be the ancient life forms that have endured such extreme conditions since when the planet was spewing all sorts of harsh elements at them.
California's little green men were discovered in the lab when the scientists were analyzing the water and mud that was collected from Mono Lake. Elena Pikuta, a microbiologist at the University of Alabama, Huntsville, states that these extremely thin and graceful bacteria move with an elegant motion. However, their cell walls are very delicate and it is difficult to keep them alive for long periods in the laboratory.
The extremophiles on Earth have been discovered around extremely hot volcanic vents, under Arctic ice, feeding on rocks beneath the sea floor, on hydrogen and in the Earth's crust and even swimming around in the waste from nuclear reactors. Most importantly, it is their ability to survive without oxygen that interests scientists."Since other bodies of the solar system (planets and moons) lack our oxygen rich atmosphere, micro-organisms that thrive without oxygen are good candidates for astrobiology research," says Richard Hoover, who is an astrobiologists at NASA's Marshall Space flight center. "If or when we find life on other planets, our first discoveries will probably be micro-organisms," he further adds.
Though it is hardly likely that Mono Lake will have a counterpart on Mars, researchers feel that it was a much larger body of water in the Pleistocene era and its level might have been 147 feet higher than it is today. According to Hoover, "by studying microorganisms found in Earth's extreme places, like Mono Lake, we can better understand how life might exist on Mars".
An organism discovered in an Arctic tunnel during an expedition came to life after 35,000 years. This calls for new studies in cryogenics. Scientists now presume that similar bacteria might exist on Mars and other bodies in the solar system. "The existence of micro-organisms in these harsh environments suggests — but does not promise — that we might one day discover similar life forms in the glaciers or permafrost of Mars or in the ice crust and oceans of Jupiter's moon Europa," says Richard Hoover.
In the 24th February 2005 issue of journal Nature, scientists reported that the bacteria that were taken 400 meters under the ocean floor came alive in the laboratory. Though researchers have suspected that there might be bacteria inside the sediments under the ocean floor but they do not know whether it would still be alive. The samples were taken from beneath the Pacific Ocean floor and 10 to 30 percent of the bacteria were alive.
"This study brings us closer to understanding the limits of life," says Lev Neretin of the Max Plank Institute of Marine Biology, in Germany. According to NASA, this is "first, fully described, validated species ever found alive in ancient ice". Hoover says that they immediately started swimming when the ice melted, adding that the bacteria frozen for thousands of years, were immediately ready to eat and multiply.
The recent discovery of blocks of ice found just under the Martian equator has made scientists optimistic of the idea that there might exist biological life in those blocks of ice, just as on Earth. The Martian ice was discovered by European researchers who estimate the age of the blocks to be between 2 to 5 million years. And Hoover is of the opinion that the microbes he found frozen on Earth could have survived millions of years. He says, "Life is far more diverse, and far more resistant to conditions we consider hostile, than was thought possible only a decade or two ago. Studying these organisms helps us understand that life may be far more widespread in the cosmos than we previously imagined".
It also proves that life though extremely fragile, is also extremely strong. And that we are just beginning to understand its role and nature in the universe. (Source: Extremophiles: Not so Extreme? by Dr Seth Shostak)
The writer fatimaS@cyber.nt.pk is a freelance contributor
|
|
|
|
