Microorganisms - Beneficial Activities (1958)

[music] [music] [music] [music] [music] Most of us think of microorganisms and especially bacteria as responsible for disease. But we often fail to realize that these same bacteria are used to make preparations which combat disease. Some microorganisms cause the destruction of useful materials. But in compost, the same organisms are essential in the decomposition of dead plants and animals. Thus, returning to the soil the same elements taken from it. The growth of microorganisms on shoes and clothing is considered undesirable. But similar organisms are necessary in the processing and flavoring of cheese as well as in the production of valuable antibiotics like penicellin. In reality, only a small number of all microorganisms are harmful. A much greater number are beneficial or essential in our lives. How can these minute forms of life cause a large animal to become sick or make substances that are useful in destroying other microorganisms? How can they produce valuable chemicals or contribute to the production of foods or aid in the growth of healthy crops? Most microorganisms exist as single cells carrying on the same life processes as do other living things. As shown by this diagram, microorganisms secrete enzymes to obtain food and energy. These enzymes cause the breakdown of complex chemical substances in the environment. The resulting substances can now enter the cell as usable foods. As metabolism of the cell continues, waste products are given off into the environment. A large variety of chemical compounds results from such activities of microorganisms. Many of these waste products are useful and have a significant effect on man and other living things. The soil is the environment for many important activities of microorganisms. All plants require chemical elements. One of the most essential is nitrogen. Where nitrogen is plentiful in the soil, plants grow vigorously. While a deficiency of nitrogen results in poor growth in nature, nitrogen is continually undergoing a cycle of changes. Legumes such as clover and soybeans play an important role in maintaining this cycle. Close examination of the roots of these legumes reveals swellings called nodules. Within these nodules are found bacteria which convert atmospheric nitrogen to usable nitrogen compounds while living in symbiosis with the plant. Other bacteria which live freely in the soil are also capable of fixing free nitrogen. When animals consume plants for food, the plant protein is converted into animal protein. When living things die, their remains containing protein nitrogen return to the soil. Here they serve as food sources for the small animals always present in soil. And for such plants as the fungi and other microorganisms, eventually this decomposition of protein releases nitrogen in the form of ammonia. Nitrifying bacteria in the soil convert ammonia to nitrates. These nitrates can now be used by all plants to build their proteins. In water log soils, certain bacteria change nitrates to atmospheric nitrogen, thus completing the cycle. To review the nitrogen cycle, atmospheric nitrogen is made available to plants by the action of nitrogen fixing bacteria, some of which grow in the nodules of legumes. The nitrogen is now changed to plant protein. In turn, when animals utilize plants as food, animal protein is built from the nitrogen in plant protein. The breakdown of wastes or of dead plants and animals by various microorganisms returns nitrogen to the soil in the form of ammonia. The ammonia is converted by nitrifying bacteria to usable nitrates in which form nitrogen is available for all plants. The dnitrifying bacteria return nitrogen to the atmosphere. and the cycle of nitrogen continues. Man's knowledge of the actions of bacteria in decomposition permits him to use these organisms in the disposal of his own waste products. In one sewage treatment process, the wastes flow to large holding tanks. When a sufficient quantity of solids has accumulated at the bottom of the tank, it is pumped to large airtight digestion tanks where bacteria normally present bring about decomposition of the complex materials. The liquid portion of the sewage flows to filter beds where it is sprayed and permitted to trickle through layers of gravel and sand. This aeration aids the bacteria that are active in the final decomposition of sewage. As we have seen, certain soil bacteria are necessary in the natural cycles of elements. Other soil bacteria have important properties that are also useful to man. Frequently, when a variety of soil microorganisms is grown on nutrient materials, some colonies can be seen to inhibit the growth of others. Clear zones around such colonies indicate the production of an antibiotic that prevents the growth of other microorganisms. Pure cultures of the organisms producing the antibiotics may be grown in tubes and then in flasks. Agitation mixes in air to encourage growth of the microorganisms. For industrial production, the antibiotic producing organisms are grown in airrated tanks of enormous capacity. The period of active growth in the large tanks may require several days for maximum yield. Then the antibiotic is separated, purified and carefully packaged. These invaluable products of microorganisms have been responsible for saving millions of human lives. Moreover, some antibiotics added to the feed of young animals promote more rapid growth. The larger pig was raised on feed containing an antibiotic. The other from the same litter was not. Many important organic chemicals are also produced by microorganisms. In the laboratory, various organisms are transferred to suitable food materials and tested to determine the chemical byproducts released during their growth. These chemicals are separated by small-scale laboratory extraction using the same microorganisms and similar methods. Large industrial concerns produce huge quantities of these valuable chemicals. The chemicals resulting from the actions of many different microorganisms find wide use in industry, the science laboratory, the hospital, and the home. Other beneficial actions of microorganisms are necessary in the dairy industry. When fresh milk is compared with sour curdled milk and examined microscopically, only a few bacteria are seen in the fresh milk. The large number of bacteria in the other sample has caused the souring of the milk by the production of acid. These acid producing bacteria can be controlled and their activities utilized. When milk in which a large quantity of these bacteria has been grown is added to a vat of fresh milk, the bacteria are allowed to grow until a kurd forms. This kurd is cut and separated from the liquid called whey. The kurd is then used for cottage and other cheese. Buttermilk also results from the action of these bacteria. The flavor and aroma of butter depend upon other bacteria. The characteristic flavor and texture of Swiss and other types of cheese likewise are due to the specific microorganisms used in their manufacturer. Still other microorganisms bring about the fermentation of sugar containing materials. Fruit juices normally contain many yeast and bacteria. The yeast may ferment the sugar in the juice to produce alcohol and the gas carbon dioxide. The bacteria present then convert the alcohol into an acid, acetic acid. The juice is now called vinegar. Certain food products, pickles, olives, sauerkraut, result from the action of other acid producing bacteria. In farm silos, these same bacteria act on freshly cut grass and other plant materials to produce the silage used to feed livestock during the winter. The carbon dioxide produced by yeast has many uses. If yeast are added to a nutrient sugar solution in a fermentation tube, then through time-lapse photography, the production of carbon dioxide by the yeast can be observed. The formation of this gas in bread making is very important when yeast are used. During setting of the dough, the yeast produce gas expanding the warm dough causing it to rise. After baking, the light texture of the bread due to the gas is revealed. We have seen that microorganisms are beneficial or even indispensable in our daily lives. But their contributions do not end here. In research laboratories, the study of these minute forms of life continues to provide man with clues to the very nature of life itself. >> [music]