Microorganisms, or microbes, are organisms that are too small to be seen by the human eye. Microbes can be fungi, bacteria, archaea, or protists, but not viruses and prions, which are commonly categorized as non-living. They are usually single-celled, or unicellular. However, there are exceptions, as some multi-cellular varieties are microscopic and some unicellular protists are visible.
Microbes can live almost anywhere on Earth where there is water. Although incredibly small, they play an important role in keeping the planet running, carrying out 90% of the Earth’s biochemical reactions. Without them, life on Earth would be destroyed. The microbes are probably the first forms of life to develop on Earth.
Microbes that live and prosper underground in high temperatures are called “thermopiles.” Dr. Bang, a microbiology professor, said that since scientists are aware that microbes existed underground, they know that the introduction of outside people, materials, and animals would have interacted with those otherwise inaccessible microbes. This interaction may have caused an evolutionary metamorphosis that went unnoticed by the world.
Scientists are indentifying factors that establish why microbes survive deep underground in some places but not others. High temperatures make certain that nothing can live too far underground. However, the availability of water, pressure, the porosity of the adjacent rock, and the flow of chemical nutrients may limit where microbes that savor harsh conditions can exist. Temperature is the primary factor in controlling how deep they can live. A lack of water and nutrients excludes subsurface life in arid regions. On the contrary, they may be more abundant deep in mid ocean ridges and salt deposits where nutrients and water flow more generously.
Rock deep underground may have scorching temperatures and toxic chemicals, but life can still survive. For example, in the early 1990’s, researchers found microbes living in rock 500 meters below the surface. More recently they have delved much deeper, nearly 3 km below ground. Tests for microbial residents and a new species of bacteria were conducted by scientists. Unfortunately, these tests cause pollution from the lubricating fluids that drillers pump into the hole. Tests on these fluids revealed a great quantity of aerobic microbes which require oxygen to survive.
In another test, scientists added a range of tracers to the drilling fluids. By checking rock samples of these man-made chemicals, they could recognize which pieces had been polluted by the drilling fluids. Finally, they measured the rock samples. The polluted type had rather large pores that allowed drilling fluid to enter the rock. Those not polluted had barred any microbes from penetrating the rock. If bacteria could not get in the rock, they also could not leave. The tight-spaced mineral grains served as cages, trapping any original bacteria for millions of years.
The organisms survive on a diet of petroleum and other organic compounds. However, because these food sources are so diluted, the microorganisms do not receive enough nutrients to grow, reproduce, or even spread throughout the rock formation. The deepest hole will introduce really high temperatures, where a lot of different biophil bacteria and water seepage reside.
Scientists recently discovered microbes living within igneous formations. These microbes are unique, relying on hydrogen, water, and carbon dioxide. Until this discovery, it was thought that products of the Earth’s interior, and other organisms to some extent, depend on the sun’s energy. Scientists in Sweden have since found a similar community of microbes deep in granite formation. These findings are of great importance because granite is one of the most abundant rocks on the continent, suggesting that these organisms are quite prevalent. Rough calculations propose that bacteria and archaea may go as deep as 4 km below the continental crust and 7 km into the oceanic crust. It has been calculated that the weight of all subterranean microbes could equal that of life above the surface.
Questions and concerns are driving investigators to explore new environments like South African gold mines. Tests on the mines reveal that bacteria survives even as deep as 3.5 km. Microbes living in high temperatures might have the potential to produce antibiotics which can be temperature tolerant. Life underground may also help solve toxic waste problems and improve methods for cleaning wastewater. The most practical application is its effect on the ethanol industry, as it can make the production process more efficient.
21. According to paragraph 1, which of the following is true of microorganisms?
22. The word “exceptions” in the passage is closest in meaning to
23. Which of the following can be inferred from paragraph 2 about microbes on Earth?
24. According to Dr. Bang, underground microbes would have interacted with
25. The word “they” in the passage refers to
26. According to paragraph 4, what is the primary factor in determining where microbes can reside?
27. The word “revealed” in the passage is closest in meaning to
28. The word “tolerant” in the passage is closest in meaning to
29. According to paragraph 8, what has been calculated about the subterranean microbes?
30. In paragraph 9, the author used “South African gold mines” as an example of
