What is bacteriology?

Science and Profession

Bacteriology is the study of
bacteria, unique life-forms that maintain the basic physiological and genetic processes of all other types of cellular life but that have the unusual characteristic of chemicophysiological diversity. Many bacteria live in totally anaerobic environments, converting carbohydrates to acids and alcohol by fermentation, nitrate to nitrogen gas, sulfate to hydrogen sulfide, and hydrogen and carbon dioxide to methane gas. Some bacteria live by photosynthetic processes similar to those of plants, while others survive by using energy obtained through the oxidation of sulfur, hydrogen, ammonia, or ferric minerals.

The history of life on Earth is closely linked to the presence of bacteria. Geologic evidence suggests the early increase in Earth’s atmospheric oxygen more than two billion years ago was the direct result of bacteriological activity. Throughout time, bacteria have continued to play a crucial role in recycling materials necessary for the survival of plants and animals. In the biosphere, bacteria are responsible for degrading and converting complex substances into useful products. Bacteria break down carbohydrates, proteins, and lipids to form carbon dioxide, and they convert ammonia to nitrate and nitrogen gas to amino acids, all of which are essential to the life cycle of plants. Bacteria are the basis of many industrial processes. Bacteria colonies are involved in producing cheeses and fermented foods such as pickles, sausage, and sauerkraut. Bacteria thriving in sewage and landfills produce methane gas, which is used as an alternative energy source by humans. The exploitation of bacteria as a detoxifying agent of environmental pollutants is becoming widespread. Almost all medically important antibiotics are produced by bacteria cultures.

Many types of bacteria live in association with animals. Most bacteria associated with humans live on the surface of the skin, in the mouth, or in the intestinal tract; the majority are harmless, and many are quite beneficial. Some bacteria, known as pathogens, are opportunistic and able to establish themselves in the body of a host, multiply, and produce local or systemic infections. Many pathogens are the causes of severe diseases in humans; most notable are anthrax, tuberculosis, bubonic plague, typhoid fever, pneumonia, gonorrhea, syphilis, gangrene, meningitis, botulism, diphtheria, scarlet fever, tetanus, streptococcal infections, and pertussis (whooping cough).

Medical bacteriology involves the study of infectious diseases produced by bacteria. Medical bacteriologists isolate bacteria suspected of being infectious, relate their role to the disease in question, study the life cycle of the bacteria colony, and seek means to provide therapy to infected victims and prevent further spread of the infectious pathogen.

Bacteriologists are highly skilled scientists who have undergone advanced studies in the fields of biology, microbiology, and chemistry; many have additional training in medical specialties such as pathology, epidemiology, and serology.

Diagnostic and Treatment Techniques

The way in which bacterial infections develop usually follows a consistent pattern. Transmission may occur by one of four pathways: direct contact, such as sneezing or sexual intimacy; inhalation; common source contacts, such as food, water, or blood; and vector-borne spreading by insects or parasites. Bacteria first invade the body through some opening, such as a wound or the skin, nose, throat, lung, intestine, urethra, or bloodstream. The bacteria then target specific cells and begin to reproduce, establishing a primary infection. If the infection remains unchecked, it may spread to the lymphatic system or bloodstream, and multiple sites of infection may develop. The resulting infection destroys local tissue by producing toxins that damage cells or by producing compounds that interfere with body metabolism.

The control of bacterial infections is accomplished by breaking the links in the chain of transmission. This can be done by altering the behavior of potential hosts through education programs, quarantine, health inspections of common source contacts, and pest eradication programs. Other efforts to control infections involve altering the defensive capability of the host. The most effective means has been through vaccination. Vaccination immunizes individuals so that they are no longer susceptible to the targeted infection. Additionally, many bacterial infections can be treated with injections or topical and oral applications of antibiotics.

Perspective and Prospects

During the mid-nineteenth century, studies by Louis Pasteur
into undesirable fermentation of beers and wines led him to the conclusion that infections in animals might be the result of some type of fermentation process. Pasteur experimented with the microbiological cause of infections by studying the characteristics of anthrax and cholera bacilli. Pasteur noted that the introduction of dead bacterial pathogens into a healthy host did not result in disease. Furthermore, if the host was injected with a virulent supply of the subject bacteria, the host did not contract the disease. The result of this work was the discovery of a method for acquired immunity to disease.

Working during the same period, German physician
Robert Koch
provided proof that anthrax and tuberculosis are caused by bacteria. Earlier in his career, Koch developed methods for isolating pure cultures of bacteria and then identifying, staining, and cataloging bacilli. This enabled Koch and other investigators to view infected blood samples and then quickly isolate and cross-reference noted bacilli with previously identified pathogens.

The groundwork that Pasteur and Koch provided helped to establish the role that microorganisms play in the development of infectious disease and ushered in a golden age of discovery into the cause of infectious diseases and their control by immunization.

Bibliography

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