MICROBIOLOGY

scientific study of microorganisms, a diverse group of simple life forms including protozoans, algae, molds, bacteria, and viruses. Research in microbiology is concerned with the structure, function, and classification of such organisms and with ways of controlling and exploiting their activities. The foundations of microbiology were established during the last half of the 19th century. The French biologist and chemist Louis Pasteur determined the role of bacteria in fermentation and disease, and the German physician Robert Koch discovered a procedure for proving that a specific organism causes a specific disease. Other investigators soon developed elaborate methods and laboratory equipment with which they revealed the ubiquity, diversity, and powerful effects of microorganisms. Many major advances have occurred in microbiology since the mid-20th century. A multitude of disease-causing microorganisms have been identified and the means of controlling their harmful effects developed. Research has, moreover, uncovered effective means of channeling the activities of various microorganisms so as to benefit medicine, industry, and agriculture. Molds, for example, are employed to produce enzymes and antibiotics, most notably penicillin. Certain bacteria also are cultivated on a large scale because they are useful in the commercial production of lactic acid, the derivatives of which are used as solvents and as a means of treating anemia and calcium deficiency. The field of genetic engineering (q.v.) led to entirely new industrial applications of bacteria, since some of those organisms that had been genetically altered were capable of synthesizing insulin and other biochemicals of great medical value. study of microorganisms, a diverse group of simple life forms that include protozoans, algae, molds, bacteria, and viruses. The field is concerned with the structure, function, and classification of such organisms and with ways of both exploiting and controlling their activities. The 17th-century discovery that living forms exist that are invisible to the naked eye was a dramatic one in man's history, for, from the 13th century onward, it had been postulated that invisible organisms were responsible for decay and disease. The word microbe was coined in the latter quarter of the 19th century to describe these organisms, all of which were thought to be related. As microbiology eventually developed into a separate science, it was found that microbes comprise a very large group of extremely diverse organisms; thus, microbiology became subdivided into various disciplinese.g., bacteriology, protozoology, and virology. The diversity of microbes, or microorganisms as they are now commonly called, has meant that it is almost impossible for one person to be knowledgeable in all of the disciplines grouped under microbiology. Microbiology involves the identification of microorganisms and the study of their structure and function. It encompasses the study of bacteria, rickettsiae, small fungi (e.g., yeasts and molds), algae, and protozoans, as well as problematical forms of life such as viruses. Because of the difficulty of assigning plant or animal status to microorganismssome are plantlike, others animal-likethey are sometimes considered a separate group called protists. Microbes can also be divided into procaryotes, which have a primitive and dispersed kind of nuclear materiali.e., the blue-green algae, bacteria, and rickettsiaeand eucaryotes, which display a distinct nucleus bounded by a membrane. Such are small algae other than the blue-greens, yeasts and molds, and protozoans. (All higher organisms are eucaryotes.) Man's daily life is interwoven inextricably with microorganisms. They abound in the soil, in the seas, and in the air. Everywhere abundant, although usually unnoticed, microorganisms provide ample evidence of their presence, sometimes unfavourably, as when they cause decay of objects valued by man or generate disease, and sometimes favourably, as when they ferment alcohol to wine and beer, raise bread, flavour cheeses, and create other dairy products from milk. Microorganisms are of incalculable value in nature, causing the disintegration of animal and plant remains and converting them to gases and minerals that can be recycled in other organisms. Additional reading Two historical works are William Bulloch, The History of Bacteriology (1938, reprinted 1979), the classic volume on the subject; and Hubert A. Lechevalier and Morris Solotorovsky, Three Centuries of Microbiology (1965, reprinted 1974), a definitive history covering the important discoveries beginning with the invention of the microscope. References include John Postgate, Microbes and Man, 3rd ed. (1992), an interesting survey of microorganisms and their role in our environment; Albert Delaunay and Romolo Deotto (eds.), The World of Microbes (1965; originally published in French, 1961), a beautifully illustrated and well-summarized account of microbes in relation to human beings; John G. Holt et al. (eds.), Bergey's Manual of Determinative Bacteriology, 9th ed. (1994), with descriptions of all genera of bacteria; Michael J. Pelczar, E.C.S. Chan, and Noel R. Krieg, Microbiology: Concepts and Applications (1993), an excellent introduction to the science of microbiology; Constantine J. Alexopoulos and Charles W. Mims, Introductory Mycology, 3rd ed. (1979), an introductory text on fungi approached from the standpoint of taxonomy and morphology; Harold C. Bold and Michael J. Wynne, Introduction to the Algae: Structure and Reproduction, 2nd ed. (1985), a general characterization of algae; O. Roger Anderson, Comparative Protozoology (1988), a comprehensive discussion of the flagellates, ciliates, and amoebas; Michael A. Sleigh, Protozoa and Other Protists, 2nd ed. (1991), a discussion of protozoa as members of the Protista; Renato Dulbecco and Harold S. Ginsberg, Virology, 2nd ed. (1988), a characterization of the biological and pathogenic properties of viruses; Jack Maniloff (ed.), Mycoplasmas: Molecular Biology and Pathogeneses (1992), a comprehensive examination of the biology and pathogenicity of mycoplasmas by more than 60 scientists; Philipp Gerhardt (ed.), Methods for General and Molecular Bacteriology (1994), a compact, comprehensive handbook of reliable, basic techniques for performing experiments in general bacteriology at the organismal and molecular level; Seymour S. Block (ed.), Disinfection, Sterilization, and Preservation, 4th ed. (1991), an extensive coverage of agents and processes for controlling microorganisms; Albert Balows et al. (eds.), The Prokaryotes, 2nd ed., 4 vol. (1992), a comprehensive reference on the biology of bacteria, including ecophysiology, isolation, identification, and applications; Albert G. Moat and John W. Foster, Microbial Physiology, 2nd ed. (1988), a description of the conditions affecting the growth of microorganisms and the biochemical changes produced by them; James Kuby, Immunology, 2nd ed. (1994), a comprehensive and richly illustrated introduction to immunology at the molecular and cellular levels; Henry D. Isenberg (ed.), Clinical Microbiology Procedures Handbook, 2 vol. (1992), a comprehensive compendium describing microbiological procedures used in the clinical microbiological laboratory; Wolfgang K. Joklik et al. (eds.), Zinsser Microbiology, 20th ed. (1992), excellent coverage of the important bacterial, viral, and fungal agents of human disease; Ronald M. Atlas and Richard Bartha, Microbial Ecology: Fundamentals and Applications, 3rd ed. (1993), general coverage of the role of microorganisms in nature; R. Campbell, Plant Microbiology (1985), an account of the relationship between microorganisms and higher plants; Ralph Mitchell (ed.), Environmental Microbiology (1992), a description of the role of microorganisms in water, soil, and the atmosphere and of methods for the control of pollution; G. Rheinheimer, Aquatic Microbiology, 4th ed. (1992; originally published in German, 5th rev. ed., 1991), a survey of aquatic bacteria and fungi and their role in the life of lakes, rivers, and seas; William C. Frazier and Dennis C. Westhoff, Food Microbiology, 4th ed. (1988), one of the standard food microbiology textbooks; and Richard H. Baltz, George D. Hegeman, and Paul L. Skatrud (eds.), Industrial Microorganisms (1993), an up-to-date account of the uses of microorganisms in industry. Michael J. Pelczar, Jr. Rita M. Pelczar The Editors of the Encyclopdia Britannica