Extremophiles are organisms that exist in extreme conditions that the human race or most oxygen dependent as well as sunlight dependent organisms cannot survive in. They are classified under archaea, a genre that was resultantly split from Kingdom Monera after an analysis of their characteristics revealed that they were significantly different from bacteria or other eukaryotic organisms.
Historical Outline
The ideal living conditions for human beings center around 22 degrees Celsius, preferably with optimal weather and a light breeze. Temperatures far below or beyond this zone are termed as extreme. Extremophiles are organisms that thrive in salty, acidic and muddy conditions with little or no oxygen. The name was first coined in 1974 by R.D. MacElroy, a renowned scientist, and literally refers to the extreme environments in which these organisms live. Detailed observations were first made in hot springs and geysers in Yellowstone National Park. These were first named thermophiles due to the fact that they managed to survive in boiling water. With time, other classes of extremophiles have been identified. The main fact is that the extremity in which extremophiles survive is measured relative to the ‘normal’ or ‘moderate’ living conditions that are optimal for humans (Silverman 1).
Extremophiles cannot be classified as bacteria. In fact, they possess characteristics exhibited by three entire domains of the classification system: Eukaroyta, Archaea, and Eubacteria. This taxonomic overlaps are indicative of the harsh living conditions, characteristic of ancient times. Hence, these organisms have triggered an in-depth quest for knowledge into the origin and evolution of the Earth. Concrete studies and advancements were first concluded in the 1960s when numerous classes of bacteria were found to exist deep into the Earth’s interior in areas formerly classified as ‘dead zones’, due to the fact that sunlight was regarded as the key to life. All underground dwelling extremophiles are classified under the larger class of endoliths. It is speculated that they have the capacity to subsist on rocks that are primarily inorganic or absorb all nutrients through veins. They are thought to come into being approximately 3.8 billion years ago. Given that the Earth is regarded as having existed for 4.5 billion years, these unicellular organisms may hold the key to the Earths past.
Central Issue
This research paper shall focus on the importance of extremophiles in the quest for knowledge about the origin of life. In addition, an in-depth research shall be conducted on the matter of usefulness of these organisms to industrial science and the possibilities of finding life on planets other than the Earth.
Extremophiles: Classification
Each and every year, scientists identify thousands of previously unknown organisms and group these under respective species, genres, classes or kingdoms. Although over 2 million species have been identified, it is speculated that the Earth contains over 100 million species. Whereas it is vital to name and catalogue these organisms, it is far more important to classify them. It is a process that necessitates an in-depth research into their characteristics. Customarily, scientists use the five-kingdom classification system as well as the three-domain classification system. However, these systems served the needs of scientists accurately until the 1970s when Carl Woese chose to classify the organisms on the basis of their genetic differences, instead of relying on their visual characteristics. Resultantly, he split a kingdom Monera into eubacteria and archaea. Extremophiles are classified under this latter group due to the fact that they possess a unique rRNA that enables them to develop particular mechanisms on their cell membranes that enable them to adapt to extreme environments (Horikoshi et al. 6-25).
Extreme Environments and Respective Types
The following list provides details of extremophiles and their respective environment. The naming system relates to the environment these organisms best thrive in (Gargaud et al. 574).
- Alkaliphile: thrives in high pH (alkaline) environments;
- Acidophiles: thrives in low pH (acidic) environments;
- Hyperthermophile: thrives in temperatures at or above 80°C;
- Thermophile: thrives in temperatures at or above 40°C;
- Psychrophile: thrives in low temperature zones;
- Cryophile: thrive in very cold zones;
- Piezophile: thrives in high pressure zones;
- Anaerobic extremophiles: live in environments that have absolutely no oxygen;
- Xerophile: live in areas with very little water.
Current Understanding/Work/Exploration by Scientists or NASA
Extreme Environments as an Indicator of Life in Other Planets
Extreme environments are rated on the basis of the possibility of human survival without the aid of special equipment. Beyond Earth, there are very few known or suspected planets that humans could live on. Therefore, the fact that extremophiles can survive in extreme environments, which are the case for other planets, presents a real possibility of the existence of life on planets other than the Earth. Various factors can lead to an environment being classified as extreme such as acidity, alkalinity/salinity, temperature (extremely hot or cold), pressure, absolute absence of oxygen, insufficient water, and presence of toxins or pollutants. Numerous studies have revealed that nowadays life does exist in those areas where previously it was accepted that it could not exist, such as volcanoes, penguin guanos, and nuclear reactors. For instance, the Science Education Resource Center has managed to decipher that the Great Salt Lake, in Utah, contains life despite the extremely alkaline conditions. Another case proved that bacteria, which were previously dormant due to the fact that they had been entombed in ice in Alaska for thousands of years, resumed normal activity once the ice thawed off (Silverman 3).
An in-depth study has been conducted by NASA on Lake Untersee in Antarctica. The lake’s waters have a high level of pH (very alkaline) similar to the optimal pH for a laundry detergent. Thus, the lake’s waters have ample methane and extremely cold temperatures that presents a distinctly superb environment for extremophiles to thrive. These conditions may be similar to those, experienced in other planets. In particular, studies suggest that these conditions are similar to those in Europa, Jupiter’s moon (Gerday & Glansdorff 408-420).
A pH level that ranges from 6.5 to 7.5 is deemed as optimal for human beings. However, acidophiles best thrive in an environment where pH level is below 5. Such an environment is best simulated by the human stomach, which is acidic due to the presence of hydrochloric acid. Acidophiles have adapted perfectly to this environment due to rRNA that strengthens their cell membranes, thereby making them impervious to stomach acids. Other acidophiles either produce biofilms or easily regulate their intra-cellular pH level to that existent in their external environment. For instance, studies in Lake Mono in California in May 2003led to the discovery of Spirochaeta Americana. This extremophile thrives best in anaerobic environments (oxygen-less) and in pH in the range of 8.0 to 10.5. The lake’s pH centers around 10 and has a high content of sulfides due to the fact that it has no outlet (terminal lake). These conditions have been compared to those in other planets that are considered as harsh or classified as those that are not able to support life. However, the fact that extremophiles, as well as algae and brine shrimp can survive in the lake’s extreme conditions indicates that life may be existent on other planets.
There are several other notable environments that have been classified as extreme, yet supporting life. Firstly, geysers, vents and extremely hot pools in Siberia contain thermophiles. Secondly, Yellowstone National Park, which is located in the United States, contains one of the most documented prooves of the existence of extremophiles in springs, geysers and zones of the high temperature, sulfur (alkalinity) as well as acidity. Thirdly, Rio Tinto in Spain and California’s Iron Mountain are overloaded with heavy metals due to substantial mining activities in these respective zones. Despite the existence of these metals, microbes primarily classified under eubacteria and archaea thrive scrappily since they have adapted to these environments either via use of biofilms for absorbing nutrients or protection (Rothschild 1-24).
Extremophiles: Work and Explorations
The most elaborate work was documented by Dr. Thomas Brock in the 1960s in Yellowstone National Park. In his investigations of the way bacteria multiply and thrive, he stumbled upon life in the park’s hot springs, a discovery in utter contradiction to the earlier claims that no life could exist in such temperatures. In particular, a bacterium, known as Thermus aquaticus, was found to exist in temperatures around 100°C, particularly, in water that was practically boiling! Brock’s discovery led to a breakthrough in three major fronts. First, T.aquaticus was named to be the first species in the new sub-division archaea. This rattled the widely held concept that sought to classify all living organisms under a five-kingdom classification system. The advancement in technology has ensured that this class of organisms is not classified as simple offshoots of bacteria. It was apparent that they had evolved and consequently divulged from eukaryotic cells as well as bacteria significantly earlier on. Secondly, extremophiles were important in the formulation of TAQ polymerase, an all-important enzyme in polymerase chain reactors (PCRs). The massive industrial application of PCRs grants researchers in the medical as well as technological field a fast means of creating millions of replicas of deoxyribonucleic Acid (DNA) over an extremely short period. Therefore, research areas primarily reliant on DNA replication, such as genetic testing and forensic science, have experienced rapid growth in the past two decades. Finally, the discovery of the existence of extremophiles has been instrumental in the illustration and proposition of possibility of life on Earth and other planets. Despite the fact that humans, as well as other oxygen-dependent organisms cannot survive on other planets, extremophiles well illustrate that there is a possibility that life could exist in these extreme environments (Gargaud et al. 574).
In the recent past, scientists have identified other extremophiles that are useful in various fields. However, none has been as vital as T. aquaticus. Some extremophiles have been found to produce proteins, resembling vital human body proteins. These proteins are responsible for averting specific autoimmune diseases as well as enigmatic conditions, such as arthritis. In addition, alkaliphiles have been instrumental in the manufacture of effective dishwashing and laundry detergents. Moreover, they are applied by the leather companies in the process of the fur removal from an animal’s skin or hide. Alkaliphiles, found in Yellowstone National Park, have been applied in paper-manufacturing industries as well as sewerage and waste treatment companies, due to the fact that these extremophiles produce proteins that synthesize hydrogen peroxide.
Current studies by NASA have concentrated on Deinococcus radiodurans. This extremophile is highly resistant to any form of radiation. In fact, these microbes were found to withstand five hundred times more radiation than any other levels that would be otherwise toxic to human beings. Whereas radiation breaks D. radiodurans DNA’s into jumbled-up pieces, the microbe automatically reassembles all unaffected and healthy pieces by shedding and excreting all non-functional parts in order to function normally again. All reassembled DNA parts are glued together via a unique enzyme. In extensive cases, complementary DNA parts are created and bonded in order to form new, long and functional strands. Although there has been no breakthrough on how these organisms manage to re-create themselves yet, intensive studies are ongoing. For NASA, a breakthrough will signify a new era of spacecraft as well as spacesuits designs (Silverman 5).
Latest Discoveries: Possible Impacts of Panspermia on the Astrobiological Field
Panspermia represents a cognitive school of thought that suggests that primitive forms of life have the ability not only to travel across planets, but also survive the ordeal. This gives rise to a highly contentious proposition that panspermia presents a solution to the long-lasting inquiry on the origin of life on the Earth. It presents scientists with the possibility that microbes could have travelled from other planets and eventually reached the Earth where they successfully became the forebears of life. In the past, this concept has been regarded as far-fetched and has been the subject of ridicule. However, recent advancements and discoveries have lent the theory more credence. A particular study carried out on tardigrades has shown that these organisms have the capability to survive for a period, lasting approximately 10 days despite the exposure to solar radiation and adverse conditions in space. Other studies indicate that various classes of lichens, invertebrates and bacteria have successfully survived despite being exposed to space. Whereas some limited form of protection may aid these organisms or provide shelter during the journey, there is an absolute necessity for optimal conditions for survival once these reach their destination (Silverman 5).
Whereas panspermia provides a group of poorly structured and unsubstantiated theorems, its integration to astrobiology provides a more concrete and insightful theorem. Astrobiology is heavily reliant on life forms such as extremophiles due to the conviction that all life forms on other planets that do not support human life thrive in extreme environments. Nonetheless, astrobiology exceeds the customary boundaries of the quest for life in other planets; it seeks to establish the origin of all life forms, their optimal environments for survival and the limiting factors to their survival.
The key to the origin of life is deemed to be held by the Last Universal Common Ancestor (LUCA), more commonly referred to as Cenancestor. Scientists suggest that all living things have a common denominator: the source of life from which all other living things evolved. It is believed that LUCA was an organism that had the capability to survive over 3 billion years ago in extreme, anaerobic conditions, presumably, an extremophile. However, scientists have failed to come to a common stand on what pre-existed before the emergence of LUCA, which are DNA-based organisms. Were they RNA-based or is the issue more complex than can be deciphered? An actual trace to the first living organism (FLO) has been rendered almost impossible.
Conclusion
Evidently, little has been documented on extremophiles. This may be due to the fact that most studies are not entirely conclusive or leave too much space for speculation. However, extremophiles present an exciting prospect and a host of opportunities for the human race. Major discoveries in the biotechnology industry as well as in microbiology have already been made and have already been implemented in the various companies for the benefit of the mankind. In addition, extremophiles provide an interesting viewpoint and a possible solution to the query as to the origin of life and the possibility of life existence on other planets. When man first reached the moon over four decades ago, an important milestone was achieved. However, since then, despite the extensive advancement in technology the progress has slowed down. Extremophiles provide the scientists with a real possibility to discover the origin of life, means of travel and possible adaptations that the human race can inculcate into their equipment in order to harness the resources of other planets. With increased funding and more discoveries, who knows where the world could be in a decade’s time?