South Carolina Aquarium Online Curriculum, 3rd

Key Points
This section will give you the main information you should know to teach the activity.

Decomposers are organisms that feed on organic material that is no longer living such as leaves, animal wastes and dead plant and animal carcasses.
Most decomposers, particularly the ones that would be on the surface of the food in this activity, are bacteria and fungi. Bacteria are microscopic single cell organisms. Fungi are organisms such as mushrooms, mold and yeast.
Both bacteria and the spores that produce fungi are easily dispersed and can be found almost anywhere. Both are microscopic and can be carried by wind and water. When landing on a moist organic surface, the bacteria begin feeding and reproducing and the fungal spores develop into their adult fungal form. Both break down the organic matter for food.
Decomposers feed on organic compounds. Inorganic compounds cannot be broken down easily by decomposers and, in some cases, can take hundreds of years to decompose. Plastics and foods with preservatives are both examples of items that decomposers have difficulty breaking down.
Decomposers are very important to a wildlife community. They remove organic wastes and the remains of plants and animals. By breaking down these remains, they return nutrients to the soil that are used by plants. Without decomposers, the soil would become so nutrient poor that it could not sustain plant life and soon the whole wildlife community would collapse.

Detailed Information
This section gives more in-depth background to increase your own knowledge, in case you want to expand upon the activity or you are asked detailed questions by students.

Decomposers play a crucial role in communities; they cause plant and animal matter that is no longer living (i.e. leaves, carcasses, and feces) to decay or rot and thus return nutrients to the soil. This process helps to recycle the nutrients that are available within communities. Fungi and bacteria are the principal decomposers that keep communities filled with nutrients that are essential for plant growth. Fungi and bacteria decompose complex molecules like sugars and proteins (that are trapped in falling leaves or in the bodies of dead organism) to nitrate, carbon dioxide, and other simple inorganic compounds that plants can use and need. Without decomposers, nitrogen, carbon and other elements would remain in wastes and corpses and would not be available for other organisms. Without decomposers, the land and the ocean would be filled with animal waste and corpses!

Bacteria are the most effective and numerous decomposers and are the first to start the process of decay. Fungi soon join the bacteria, followed later in the cycle by organisms like centipedes, beetles, millipedes, and earthworms.

Many items in your refrigerator or growing in your yard are potential food for decomposers. Organic materials contain carbon and nitrogen- nutrients that provide energy and growth to microorganisms, like bacteria.

All organic materials have a ratio of carbon to nitrogen (C:N) in their tissues. Leaves are high in carbon while vegetable scraps are higher in nitrogen. The C:N ratios are significant because tiny decomposers need about 30 parts of carbon for every 1 part of nitrogen in the organic material. If the ratio is greater than 30:1, nitrogen will be lacking, and materials will decompose more slowly. Anything organic will decay, however it may take longer when the C:N ratio is too high. Note that foods with synthetic preservatives or foods containing natural preservatives (like vinegar or salt) will decay more slowly than foods that do not contain any type of preservative. Inorganic materials, like plastics and other human made synthetic materials, can take months to hundreds of years to decompose.

Average Carbon to Nitrogen Ratios for Organic Materials

Vegetable scraps	12-20:1
Coffee grounds	20:1
Grass	12-25:1
Leaves	30-80:1
Bark	100-130:1
Paper	150-200:1

From Clemson Extension’s Recycling Yard Trimming: Home Composting. Information Leaflet 48. Revised April 1996.

The fuzzy stuff that grows on foods that have been left in the refrigerator or out on the shelf for too long is mold. Mold, mushrooms, truffles, yeast, and the blue streaks in blue cheese are all types of fungus. The pharmaceutical industry grows fungi to make antibiotics, chemicals that are produced by one organism that inhibits the growth of or kills another organism. In 1928, Alexander Fleming was studying bacteria and accidentally contaminated one of his bacterial cultures with a strain of the Penicillum fungus. He observed that the fungus killed his bacteria. We now know that many fungi secrete antibiotics as weapons against bacteria that may be competing with the fungus for food or attacking the fungus. Ten years later, Howard Florey purified penicillin and began marketing it as an antibiotic to treat bacterial infections in people.

Unlike green plants, fungi do not grow from seeds they grow from spores. Also unlike plants, fungi have no chlorophyll and cannot make their own food by harvesting energy from the sun. Fungi feed by producing chemicals that make things, like food, rot. As the food rots, the fungus grows. Remember that mold is a type of fungus and there are many different types of mold. The mold that grows on bread initially looks like white, fuzzy cotton, but after a week will turn black. The black color is due to the presence of hundreds of tiny spores.

Believe it or not, the air is so loaded with spores from fungi that as soon as an animal dies or a leaf falls, it is covered with spores from fungi. Spores can be carried by wind or water, but need to land in a moist place to germinate (to begin to grow). Therefore, the best way to protect materials from mold is to keep them as dry as possible. Some fungi can be detrimental to humans. The British, during the Revolutionary War, lost more ships to wood rot caused by fungus than they did to enemy attack. In the humid environment of South Carolina, wooden homes are attacked by mold. Ringworm and Athlete’s foot are examples of diseases that fungi cause in humans.

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South Carolina Aquarium Spotlight Organisms

Bacteria & Fungi
Decomposers can be found not only in each and every exhibit within the Aquarium, but just about everywhere, though you would need a microscope to be able to see most of them. One type of decomposer, bacteria, is living all around us. Anton van Leeuwenhook, the inventor of the microscope, said, "There are more [things] living in the scum in a man's mouth than there are men in a whole kingdom." Though too small to be seen, bacteria are abundant across the earth. Though some bacteria are photosynthetic or cause diseases, many are decomposers helping to break down dead plant and animal matter.

Fungi are not as hard to see. Anyone who has seen a mushroom or seen mold on bread has seen a fungus. Like bacteria, most fungi are decomposers. Fungi have the potential to be just about anywhere, because they reproduce by spores. Spores are microscopic and easily dispersed by wind or water. When a spore lands on a moist organic surface, it will begin to germinate and then will develop into an adult mushroom or mold, feeding as it grows. In the South Carolina Aquarium, fungi will likely grow in exhibits that contain soil, that are moist, and that contain dead material, like leaves. Look for fungi in the mountain forest aviary and the blackwater swamp exhibit.

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