Some bacteria are helpful

The most important role of bacteria is ecological. Bacteria help us by breaking down the tissues of dead organisms. The breakdown process – decomposition – happens as bacteria use the nutrients in dead tissues for food. Without bacteria, piles of dead organisms would cover the earth.

When decomposition takes place, bacteria release certain chemicals as waste products. Some of these chemicals serve as important raw materials for growing plants. Without bacteria, the continuous cycle of life could not continue.

Some bacteria and some species of blue-green bacteria live on the roots of certain plants. These bacteria change nitrogen from the air into chemicals that the plants can use. Thus, ‘‘factory made” fertilizer is not needed to help these plants grow.

Some bacteria decompose sewage and other wastes in water. In this way, bacteria can help keep lakes and streams free from small amounts of pollution. Many types of bacteria are used in food production. The genus Lactobacillus, for instance, is noted for its effect on milk products, producing buttermilk, yogurt, sour cream, cheese, kraut and other foods. Lactobacilli are also used in the commercial production of sauerkraut and pickles.

Life scientists often use bacteria in their laboratories for research because they are simpler than other cells and they reproduce very quickly. Experiments using bacteria help scientists study DNA, RNA, cancer, viruses and the life processes.

Some bacteria are harmful

Even through most bacteria are helpful to us, some are harmful.

Bacteria help us make certain foods. But they can also cause large losses of food through decay, spoilage, and poisoning. We try to slow down the growth of harmful bacteria by drying, freezing, refrigerating, preserving, pasteurizing, or boiling our food. Bacteria play an enormous role in spoiling food and other stored organic products, and some organisms of this type are pathogenic. Botulism is a deadly kind of food poisoning caused by a species of bacteria. Food poisoning is caused by Clostridium botulinum, an obligate anaerobe. It is rare, but very dangerous. Spores of this pathogen may survive heating to temperatures as high as 100⁰C, that’s why they may not be killed if process is faulty. Then bacteria will grow and produce toxin in oxygen less environment.

Bacteria that cause disease are called pathogens. They can damage the living tissues in your body and make materials that are poisonous to you. Pathogenic bacteria cause hundreds of diseases, such as strep throat, pneumonia, tuberculosis, cholera, diphtheria and tetanus in humans and in the other organisms (Chart 1). Yersinia pestics, for example, is the bacterium responsible for a disease called plague or Black Death, which killed one out of every four people in Europe in 1348-50. Airborne bacteria of the genus Streptococcus cause other serious diseases, including scarlet and rheumatic fever. Tuberculosis and whooping cough are also airborne bacterial diseases.

A lot of bacterial diseases are spread in food or water. Undulant fever, brucellosis, is usually contracted through drinking milk or eating milk products from an infected cow. Pasteurization of milk destroys the causative agent, Brucella, and the disease can be controlled in animals by immunization.

Syphilis and gonorrhea, caused by a spirochete and a diplococcus, respectively, are transmitted by sexual intercourse. Syphilis may also be transmitted by an infected mother to her unborn child and gonorrhea, if present in the genital tract of the mother, can infect the eyes of an infant as it passes through the vagina to birth.

The most dangerous wound-infecting bacteria are members of the genus Clostridium. They are soil dwellers, form spores, so any wound exposed to soil is probably exposed to Clostridia. Clostridium produces a toxin that affects the nervous system and causes muscle spasms. Clostridium perfinge creates destruction of tissue and gas gangrene (accumulation of gases as the result of bacterial activity).