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Microbes are the oldest life-forms and the foundation for all of life. They are prokaryotic in

nature, though extremely small; they have the most important impact on our world.

In the modern world, the microbes are found everywhere and fulfill numerous roles. Most are

harmful, but many are also beneficial in the environment. From the air we breathe to the soil we

rely on for farming to the water we drink, everything humans need to survive is intimately

coupled with the activities of microbes. In the oceans, algae, protozoa and bacteria are the most

numerous and important members of the plankton communities that are the basis of all marine

food chains.

The microbes can reproduce a generation through binary fission within 1-3 hrs. Reproduction is

limited due to nutrient exhaustion, metabolic waste poisoning, or being consumed by other

organisms. They also face competition from other microorganisms. Some microbes can survive

under harsh conditions and where there is no food like the Bacillus anthracis.

Microbes perform innumerable functions on earth;

On land, bacteria dominate in soils and are the most important decomposers, being responsible

for the recycling of almost all organic materials and without them eukaryotes would not exist.

The microbes help recycle chemicals and clean up the environment. They play a defining role in

the chemical cycle as they are nitrogen producers and decomposers.

Bioremediation; here organisms are used to remove pollutants from soil, air, or water. In sewage

systems: they decompose sludge that can later be used as fertilizer. Bacteria produce compoundsthat help certain Achaea consume methane, a greenhouse gas. Liquid wastes that are put into a

trickling filter system are mixed with microbes that absorb its organic material that is later

released into a body of water.

They have also been used to carry out chemical transformations of inorganic materials in order to

make those products less mobile or bioavailable in the environment. Fertilizers make oil eating

bacteria that can help clean up oil spills. Microbes aid in mining operations. Bacteria are used in

microbial enriched oil recovery and to extract precious materials from ore.

They can be used to manufacture biofuel and other energy products. Bacteria are used to digest

corn and sugarcane in the manufacture of ethanol, and researchers are exploring their use in

transforming chemical energy into electrical energy in microbial full cells.

Hundreds of species of microbes live in and on the surface of the human body. They supply

vitamins to the body and help it digest food.

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Microorganisms are the chief causes of transmittable diseases and affect the evolution of their

hosts as weaker organisms succumb to disease while stronger individuals survive to pass on their

genes.

Bacteria are used to digest grasses and other fodder to make silage, a feed material that can be

stored for use during winter months when pastures are not available. Also, legume seeds, such as

beans and peas, are often coated with nitrogen-fixing bacteria prior to planting to ensure the

plants develop the proper nitrogen-fixing community

Microbes are used in food manufacture in many different capacities, including fermentation

processes and flavor enhancement. Microbes are also significant in terms of food spoilage and

food safety. There have been enormous food recalls due to microbial contamination.

Heat stable enzymes isolated from thermophilic bacteria, like Taq, lipase, esterases and others,

have proven extremely useful in biotechnology.

These roles are all important but it is four billion years ago that microorganisms changed the

earth forever.

Life evolved from large organic molecules about four billion years ago with the earth still hot

with a toxic atmosphere. The boundary from non-life to life was crossed when RNA and DNA

molecules started self replicating thus using proteins and lipids to encase and protect themselves

in the first cells. The cells lacked nuclei and all the other organelles. Though the cells were

primitive they were capable of growing, movement and reproduction. This lead to the shaping of

the earth's atmosphere and future evolution over a period of one to three billion years ago

Heterotrophs were the fist microbes and fed on loose organic molecules, nutrients and each

other. At the time when there was shortage of available nutrients, the cyanobacteria used the

pigment chlorophyll to trap sun energy which was used to make sugars from water and carbon

dioxide. That brought about the first autotrophs which are the ancestors of modern blue green

algae that totally alter the earth's atmosphere through production of oxygen which is a by-

product of photosynthesis.

In the next three billion years, evolution of microbes continued that led to development of the

ability to manufacture a huge number of chemicals, becoming sophisticated biochemical

factories. Organelles were also developed organelles to become more efficient like the nuclei

evolved where the chromosomes are stored and also control functions of the cells.

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Ribosomes also developed and other cell organelles which were vital for cells to join together

forming multicellular organisms. Without those biochemical abilities of individual cells,

multicellular life would not have been possible. Our structures and abilities all come from the

information stored at the cellular level and the chemicals that they can make; all this was made

possible by the microorganism ancestors.

Another evolutionary progress made was the ability of microbes to undergo sexual reproduction.

This advance led to the explosion of life forms in the Cambrian Period. Until that point,

evolution could only occur due to mutations which process is slowly. As a result of the sexual

reproduction and subsequent genetic recombination, new forms of life have evolved quickly.

In the Cambrian Period there was enough oxygen in the ocean and the atmosphere for numerous

new aerobic life forms to evolve. All the major phyla of animals appeared in this period and life

was experimenting on a grand scale with all the potential shapes, forms and types. Some

succeeded while others became extinct, but in all that period and up to the present, the microbes

continued to survive, compete, thrive and adapt. Some took on parasitic traits so as to take

advantage of larger multicellular hosts to protect themselves.

Parasites and disease-causing microorganisms are important in driving natural selection, taking

out weak individuals and thus promoting the evolution of fitter species. The microbes are

responsible for disease and can cause death. Disease is harmful to the population but when this is

looked at from the perspective of the ecosystem can result in an overall benefit. Disease is more

likely to eliminate those organisms that are weak and in so doing they make room for the

stronger to survive and become healthier which in the long run can lead to a stronger

environment.

Many higher organisms also took advantage of microorganisms and formed symbiotic

relationships with them. Without microorganisms, termites could not digest wood and cows

could not digest grass. We too are dependent on our gut flora to help digest our food. Virtually

every plant and animal has symbiotic bacteria that they are dependent upon for their survival.

As the primary roles played by microorganisms is decay, without the elimination of dead

biological material there is no way for the various cycles of life to continue. Microscopic

bacteria, fungi and animals consume dead plant and animal material. In so doing they release the

carbon and nutrients that are tied up in the structures of these dead organisms releasing them

back to the soil and the atmosphere.

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In the oceans, microscopic plants and animals, phytoplankton and zooplankton, gather nutrients

in the waters and make up the base of the oceanic food chain. Consumed by the smallest and the

largest of ocean life these microbes are the key to life on the planet.

Phytoplanktons, microscopic plants, absorb nutrients and carbon dioxide dissolved in the oceans

water. Through photosynthesis they combine the carbon dioxide with water to make sugars. This

process is the same as that used by trees and grasses and all other plants.

Zooplanktons, microscopic animals, consume phytoplankton as well as bits of dead life whether

floating in the oceanic currents or fallen to the sea beds. As the next step in the food chain of the

oceans, zooplanktons are also essential to life. Macroscopic free floating shrimp, jellyfish and

other animals are considered zooplankton since they are invisible to the naked eye.

Another form of plankton is the bacterioplankton which act in a manner similar to both

phytoplankton and zooplankton, but because of their cellular structure, bacterioplankton can't be

considered as any of the above. However, some bacteroplankton have chloroplasts and can

perform photosynthesis, like phytoplankton. Others can't do that and serve in the same ecological

niche as zooplankton.

Zooplanktons consume phytoplankton and bacteroplankton, as well as one another. Also living

on these microorganisms are the small filter feeders such as clams and coral. But, even the

largest animals on the planet survive on plankton. Large baleen whales are filter feeders. Using

structures in their mouth to bring in enormous quantities of ocean water, these giant animals

separate the plankton from the water for sustenance. Even the largest fish in the oceans, whale

sharks, oceanic sunfish and giant manta rays, survive by filtering plankton from the seas.

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