Have you ever wondered what kind of organisms live in volcanic sulfur springs like at Yellowstone Park or in deep-ocean hydrothermal vents? Or questioned why the world is not filled with twigs, leaves, and undecayed bodies? Microscopic life covers nearly every square centimeter of Earth. These small organisms play a significant role in our lives. They are found in the air, on our skin, and deep beneath the surface thriving; even under extremely harsh conditions.
The smallest and most common microorganisms are Prokaryotes -unicellular organisms that lack a nucleus. They typically range is size from 1 to 5 micrometers.
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Biologists have divided prokaryotes into two different groups: the Bacteria and the Archaea. Although prokaryotes are physically different than eukaryotes (organisms whose cells contain a nucleus and membrane bound compartments) prokaryotic cells perform many functions that enable them to survive, reproduce, thrive and dominate the living world. Some prokaryotes achieve these functions under extreme environmental conditions such as high temperatures, or low pH.
Extreme halophiles, which are salt-loving archaea can live at very high salt concentration such as in Great Salt Lake and even the Dead Sea. Although eukaryotes are far more complex than prokaryotes; these conditions are intolerable for eukaryotes. Another group of archaea is the Methanogens, prokaryotes that produce methane gas. These archaea live in oxygen-free environments such as anoxic mud and the digestive tract of some animals, especially in the rumen of cows and other grazing animals. The methanogens use hydrogen and carbon to produce methane (CH
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). In the atmosphere, the methane reacts with oxygen to produce CO
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. Without methanogens Earth would be a really different place and oxygen would make up a much greater percentage of the atmosphere.
A most fascinating group of bacteria, however, are the cyanobacteria. They were once classified as " blue green algae". These bacteria have an elaborate and highly organized system of internal membranes, which enables them to function in photosynthesis, a process by which cells convert energy of sunlight into chemical energy. Organisms that perform photosynthesis require sunlight. Therefore, they are only found in terrestrial and aquatic environments where sufficient light can penetrate. Cyanobacteria perform photosynthesis in a similar way to some eukaryotic algae and plants. Some types of cyanobacteria can transform molecular nitrogen into a form usable by plants.
This unit will reveal many interesting and amazing facts about the role of bacteria –organisms that came into existence billions of years before us, in our lives and in natural ecosystems. Through this unit, students will expand their horizons by learning more about the wonders of bacteria.
