Bacteria are microscopic, single-celled organisms that exist all around you and inside you. Although they can cause sickness and disease, they are very important to life on Earth. We depend on bacteria to help in the digestion of food, for plant growth, and to help us make foods and medicines. Bacteria are an important part of the soil. They are able to capture some nutrients that plants cannot. When living things die, bacteria play a very important role as decomposers, bacteria and fungi feeding on and breaking down plant and animal matter. Without these decomposers, the bodies of all organisms that have ever lived would still remain. This would be messy. When bacteria break down the dead organisms, they release substances that can be used by other organisms in the ecosystem. Bacteria can affect our bodies in several ways. Harmful bacteria can make us sick, but fortunately, our bodies will fight back. When streptococcus bacteria give us strep throat we can take medicine to help us get well faster. Some bacteria always live in our bodies. They are found in digestive systems and help digest food. Other bacteria are in our food. When you eat yogurt or cheese, you eat bacteria. Bacteria are the smallest microorganisms. We can see them when there are thousands of them growing together in a colony. To see baceria as a single organism, requires a microscope with very high magnification. Bacteria live in almost every place on Earth. Scientists can culture, grow microorganisms in a specially prepared nutrient medium. The drawing shows how colonies of bacteria look when cultured on a plate. The colonies vary in size and color depending on the type of bacteria.
Harmful Effects of Bacteria to Human Affairs
Harmful Effects of Bacteria to Human Affairs are as follows: 1. Pathogenic bacteria: These bacteria cause great losses to animal and plant life by causing various diseases in them. Cholera, typhoid, pneumonia, dysentery, tuberculosis, tetanus, etc., are more common human diseases. ‘Ring disease of potato’, ‘yellowing rot of wheat,’ ‘Citrus canker,’ ‘wilt of cucumber’ and ‘crown gall’ are the common bacterial diseases of plants. 2. Food spoilage: Some saprophytic bacteria grow on unprotected foodstuffs like fruits, pickles, jams, jellies, bread, etc., and spoil them by causing decay. The use of salt, sugar and oil, etc., in preservation of pickles and jams, checks the growth of such bacteria. Clostridium botulinum produces a very virulent poison in canned food and many deaths occur due to it. 3. Loss of fertility: Anaerobic bacteria such as Bacillus denitrificans reduce the nitrates of the poorly aerated soil to nitrites and then to ammonium compounds, and free nitrogen is liberated. Thus the amount of readily available nitrogen goes to the atmosphere. They are known as denitrifying bacteria.