INTRODUCTION The environments of Earth include conditions in which physical and chemical extremes make it very difficult for organisms to survive. Conditions that can destroy living cells and biomolecules include high and low temperatures; low amounts of oxygen and water; and high levels of salinity, acidity, alkalinity, and radiation. Examples of extreme environments on Earth are hot geysers and oceanic thermal vents, Antarctic sea ice, and oxygen-depleted rivers and lakes. Organisms that have evolved special adaptations that permit them to live in extreme conditions are called “extremophiles. ”
Photo by: Dmitry Pichugin “Thermophiles” are microorganisms with optimal growth temperatures between 60 and 108 degrees Celsius, isolated from a number of marine and terrestrial geothermally-heated habitats including shallow terrestrial hot springs, hydrothermal vent systems, sediment from volcanic islands, and deep sea hydrothermal vents. -Encyclopedia of Environmental Microbiology, 2002. vol. 3. Temperature and bacteria The lowest temperature at which a particular species will grow is the minimum growth temperature, while the maximum growth temperature is the highest temperature at which they will grow.
The temperature at which their growth is optimal is called the optimum growth temperature. In general, the maximum and minimum growth temperatures of any particular type of bacteria are about 30°F (-1°C) apart. Most bacteria thrive at temperatures at or around that of the human body 98. 6°F (37°C), and some, such as Escherichia coli, are normal parts of the human intestinal flora. These organisms are mesophiles (moderate-temperature-loving), with an optimum growth temperature between 77°F (25°C) and 104°F (40°C).
Mesophiles have adapted to thrive in temperatures close to that of their host. Psychrophiles, which prefer cold temperatures, are divided into two groups. One group has an optimal growth temperature of about 59°F (15°C), but can grow at temperatures as low as 32°F (0°C). These organisms live in ocean depths or Arctic regions. Other psychrophiles that can also grow at 32°F (0°C) have an optimal growth temperature between 68°F (20°C) and 86°F (30°C). These organisms, sometimes called psychrotrophs, are often those associated with food spoilage under refrigeration.
Thermophiles thrive in very hot environments, many having an optimum growth temperature between 122°F (50°C) and 140°F (60°C), similar to that of hot springs in Yellowstone National Park. Such organisms thrive in compost piles, where temperatures can rise as high as 140°F (60°C). Extreme thermophiles grow at temperatures above 195°F (91°C). Along the sides of hydrothermal vents on the ocean bottom 217 mi (350 km) north of the Galapagos Islands, for example, bacteria grow in temperatures that can reach 662°F (350°C). pH and bacteria
Like temperature, pH also plays a role in determining the ability of bacteria to grow or thrive in particular environments. Most commonly, bacteria grow optimally within a narrow range of pH between 6. 7 and 7. 5. Acidophiles, however, prefer acidic conditions. For example, Thiobacillus ferrooxidans, which occurs in drainage water from coal mines, can survive at pH 1. Other bacteria, such as Vibrio cholera, the cause of cholera, can thrive at a pH as high as 9. 0. Osmotic pressure and bacteria Osmotic pressure is another limiting factor in the growth of bacteria.
Bacteria are about 80-90% water; they require moisture to grow because they obtain most of their nutrients from their aqueous environment. Examples of Extreme Communities Deep Sea. The deep sea environment has high pressure and cold temperatures (1 to 2 degrees Celsius [33. 8 to 35. 6 degrees Fahrenheit]), except in the vicinity of hydrothermal vents, which are a part of the sea floor that is spreading, creating cracks in the earth’s crust that release heat and chemicals into the deep sea environment and create underwater geysers.
In these vents, the temperature may be as high as 400 degrees Celsius (752 degrees Fahrenheit), but water remains liquid owing to the high pressure. Hydrothermal vents have a pH range from about 3 to 8 and unusual chemistry. In 1977, the submarine Alvin found life 2. 6 kilometers (1. 6 miles) deep near vents along the East Pacific Rise. Life forms ranged from microbes to invertebrates that were adapted to these extreme conditions. Deep sea environments are home to psychrophiles (organisms that like cold temperatures), hyperthermophiles (organisms that like very high temperatures), and piezophiles (organisms adapted to high pressures).
Hypersaline Environments. Hypersaline environments are high in salt concentration and include salt flats, evaporation ponds, natural lakes (for example, Great Salt Lake), and deep sea hypersaline basins. Communities living in these environments are often dominated by halophilic (salt-loving) organisms, including bacteria, algae, diatoms, and protozoa. There are also halophilic yeasts and other fungi, but these normally cannot tolerate environments as saline as other tax. Deserts. Deserts can be hot or cold, but they are always dry.
The Atacoma desert in Chile is one of the oldest, driest hot deserts, sometimes existing for decades without any precipitation at all. The coldest, driest places are the Antarctic Dry Valleys, where primary inhabitants are cyanobacteria, algae, and fungi that live a few millimeters beneath the sandstone rock surface. Although these endolithic (living in rocks) communities are based on photosynthesis, the organisms have had to adapt to long periods of darkness and extremely dry conditions.
Light dustings of snow that may melt in the Antarctic summer are often the only sources of water for these organisms. Ice. Permafrost, and Snow. From high-altitude glaciers, often colored pink from red-colored algae, to the polar permafrost, life has evolved to use frozen water as a habitat. In some instances, the organisms, such as bacteria, protozoa, and algae, are actually living in liquid brine (very salty water) that is contained in pockets of the ice. In other cases, microorganisms found living on or in ice are not so much ice lovers as much as ice survivors.
These organisms may have been trapped in the ice and simply possessed sufficient adaptations to enable them to persist. Atmosphere. The ability for an organism to survive in the atmosphere depends greatly on its ability to withstand desiccation and exposure to ultraviolet radiation. Although microorganisms can be found in the upper layers of the atmosphere, it is unclear whether these constitute a functional ecosystem or simply an aerial suspension of live but largely inactive organisms and their spores. Outer Space.
The study of extremeophiles and the ability of some to survive exposure to the conditions of outer space has raised the possibility that life might be found elsewhere in the universe and the possibility that simple life forms may be capable of traveling through space, for example from one planet to another. Research Findings Newfound gene may help bacteria survive in extreme environments Resulting microbial lipids may also signify oxygen dips in Earth’s history. Jennifer Chu, MIT News Office July 26, 2012 A newly discovered gene in bacteria may help microbes survive in low-oxygen environments.
A bacterial cell with the gene, left, exhibits protective membranes. A cell without the gene, right, produces no membranes. Image: Paula Welander In the days following the 2010 Deepwater Horizon oil spill, methane-eating bacteria bloomed in the Gulf of Mexico, feasting on the methane that gushed, along with oil, from the damaged well. The sudden influx of microbes was a scientific curiosity: Prior to the oil spill, scientists had observed relatively few signs of methane-eating microbes in the area. Now researchers at MIT have discovered a bacterial gene that may explain this sudden influx of methane-eating bacteria.
This gene enables bacteria to survive in extreme, oxygen-depleted environments, lying dormant until food such as methane from an oil spill, and the oxygen needed to metabolize it become available. The gene codes for a protein, named HpnR, that is responsible for producing bacterial lipids known as 3-methylhopanoids. The researchers say producing these lipids may better prepare nutrient-starved microbes to make a sudden appearance in nature when conditions are favorable, such as after the Deepwater Horizon accident.
The lipid produced by the HpnR protein may also be used as a biomarker, or a signature in rock layers, to identify dramatic changes in oxygen levels over the course of geologic history. “The thing that interests us is that this could be a window into the geologic past,” says MIT Department of Earth, Atmospheric and Planetary Sciences (EAPS) postdoc Paula Welander, who led the research. “In the geologic record, many millions of years ago, we see a number of mass extinction events where there is also evidence of oxygen depletion in the ocean.
It’s at these key events, and immediately afterward, where we also see increases in all these biomarkers as well as indicators of climate disturbance. It seems to be part of a syndrome of warming, ocean deoxygenation and biotic extinction. The ultimate causes are unknown. ” Welander and EAPS Professor Roger Summons have published their results this week in the Proceedings of the National Academy of Sciences. This image shows that 5 different extreme environments that the extremeophile live. Such as, Sea Vennts at sea floor, Yellowstone Hotsprings, Antartica Subglacial Lakes, at Atacama Desert, and lastly at Jupiter (Space).
Europa is one of Jupiter’s moons, and is covered in ice. Scientists have recently uncovered strong evidence of liquid water beneath Europa’s ice, which may be due to hydrothermal vents, which may in turn host bacteria. Credit: Nicolle Rager Fuller, NSF REFFERENCES 1. http://science. jrank. org/pages/714/Bacteria. html#ixzz28JlGDpue 2. Horikoshi, K. , and W. D. Grant. Extremophiles: Microbial Life in Extreme Environments. New York: Wiley-Liss, 1998. 3. Madigan, M. T. , and B. L. Marrs. “Extremophiles. ” Scientific American 276, no. 4 (1997): 82–87. 4.
Rothschild, L. J. , and R. L. Mancinelli. “Life in Extreme Environments. ” Nature 409 (2001): 1092–1101. 5. Seckbach, J. , ed. Journey to Diverse Microbial Worlds: Adaptation to Exotic Environments. Dordrecht, Netherlands: Kluwer Academic Publishers, 2000. 6. http://www. biologyreference. com/Ep-Fl/Extreme-Communities. html#b#ixzz28Jn5EptD 7. http://www. nsf. gov/news/special_reports/sfs/index. jsp? id=life;sid=ext ASSIGNMENT 1 BACTERIAS THAT LIVE IN EXTREAM ENVIRONMENT NAME : SARANKUMAR PERUMALU MATRIX NO : 4112033021 LECTURER : MR MOOHAMAD ROPANING SULONG
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