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Microecology is a large field which includes many topics such as evolution, biodiversity, exobiology, ecology, bioremediation, recycling, and food microbiology. There is an estimated 10,000,000 different type of microbes that live on this planet of which fewer than 4500 have been described according to the General Biodiversity Assessment (1) http://www.isme-microbes.org/whatis/biodiversity.
Without a microscope, the human eye can only see objects larger than one-tenth of a millimeter long, but given the right conditions, you might be able to see a human egg. Looking down at these tiny objects, you are looking at the edge of an entire world of creatures invisible to the naked eye. In this land around us, tiny microbes live out their tiny lives. Like us, they eat, move and reproduce. They interact with their world, obtaining food and energy from the environment, but also changing it in some very large ways. With millions of different kinds of microbes existing today, these organisms cover every part of the Earth. They are versatile in that they live in just about every kind of habitat. Over the billions of years that they have existed on the planet, microbes have adapted to fit their environments, developing ways of gathering food and energy that are still used by most organisms today. (2) http://microbes.org/microscopic-worlds Microbes are incredibly diverse, they can survive in environments from very cold to the extremely hot. They are also tolerant of many other conditions, such as limited water availability, high salt content, and low oxygen levels. Not every microbe can survive in all habitats. Each type of microbe has evolved to live within a narrow range of conditions.
Microbes are part of every ecosystem. They form the foundation of many food webs. Microbes are eaten by animals, which then serve as food sources for other animals and plants. Microbes also play an important part in breaking down dead plant and animal material through decomposition. Microbes are involved in the cycling of nutrients and other compounds throughout the environment. For example, microbes in the soil decompose the plant and animal matter in the rainforest creating a rich and fertile growing environment.
Terrestrial microbial habitats
Only one percent of microbes that live in soil have been identified. These organisms take part in the formation of soil, and are essential components of their ecosystems. They are responsible for the transfer of nutrients to plants and animals through various cycles. Some microbes convert nitrogen from a gas to a form that plants can use, like natural fertilizer. Without the microbes, many plants would not be able to grow. Bacteria and fungi that live in soil feed mostly on organic matter. They promote the decomposition of dead material, which releases useful nutrients into the soil. Microbes the primary members of the soil food web. These microbes are very sensitive to their local environment. Factors such as the levels of carbon dioxide and oxygen, the pH, moisture and temperature all affect the growth of microbes in the soil.
Aquatic microbial habitats
Microbes live in both fresh and salt water. These organisms include microscopic plants and animals, as well as bacteria, fungi and viruses. As with other microbes, the ones that live in water are adapted to the specific conditions of their environment. Habitats range from ocean water with an extremely high salt content to freshwater lakes or rivers. The temperature of aquatic environments also varies, with microbes living in hot springs, as well as extremely cold Arctic waters. Aquatic microbes also live in the groundwater beneath the earth, and in tiny pockets of water that occur on land that are both natural and manmade. Like their terrestrial counterparts, aquatic microbes play an important role in the cycling of nutrients throughout water ecosystems. They promote decomposition by breaking down dead aquatic sea life. This leads to the release of nutrients into the water. In addition, microbes serve as food for animals, such as marine worms that eat bacteria and fungi living in the aquatic sediments. One of the most important roles of aquatic microbes is the production of oxygen by phytoplankton. These microbes release oxygen as they harness the energy of the sun during photosynthesis.
Microbial habitats in other organisms
Microbes can be found in just about every environment on the planet. This includes living on other plants and animals, even humans. The human body has about 10 trillion cells. Ten times as many microbes live on or inside the body, with thousands of different kinds. No two people have exactly the same mix of microbes, making our personal microbial ecosystem even more unique. Microbes also live on other organisms. As with the ones found on people, these microbes can be harmful or beneficial to the host. For example, bacteria grow in nodules on tubular plants. These microbes convert nitrogen from the air into a form that the plants can use. Cows have microbes living in their rumen — the special stomach where digestion of grass and feed occurs. In many ways, animals and plants have evolved as habitats for the millions of microbes that call them home.
Extreme microbial environments
Microbes survive in some amazing places, like in hot water springs, or around deep sea vents. Because the environments are so extreme the microbes are called extremophiles. This means that they love the extreme conditions of their habitat. The extremophiles are so well adapted to their own environment that many cannot grow when brought back to the laboratory, unless the special conditions are recreated exactly as the ecosystem that the microbe came from. Microbes each have their own idea of what perfect living conditions are, just like humans do. Some, like the ones in hot springs, need extreme temperatures to grow. Others thrive when the salt concentration of water is very high, as is found in parts of the ocean and land locked salt water lakes. There are even microbes that live inside rocks, or in the pores between grains of minerals. These microbes can live deep within the Earth. Extremophiles are more than just interesting creatures. Scientists have used their abilities for other purposes. Compounds made by extremophiles have contributed to laundry detergent designed for hot water, and are used in special techniques for copying DNA.
Extraterrestrial microbial habitats
It is possible microbes may have been carried to Earth from other planets or asteroids. So far, no microbes have been found outside this planet, but the field of extraterrestrial microbiology continues to flourish. The existence of microbes living in extreme environments on Earth has encouraged scientists to seek out these tiny life forms in harsh places on other planets like Mars. Space probes sent to Mars have searched for microbes living there. While it is extremely difficult to grow microbes remotely, scientists can look for signs of their activity. This includes the breakdown of nutrients, or the creation of gases.