Microbiology

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MICROBIOLOGY

MICROBIOLOGY is the study of organisms beyond the scope of human vision, particularly bacteria, viruses, algae, fungi, and protozoa. Since its founding in the nineteenth century, the science has largely focused on the isolation, identification, and elimination of pathogens from humans, animals, plants, food, and drinking water. Microbiologists have also examined nonpathogenic forms, seeking to understand their structure, function, and classification in order to control or exploit their activities.

Microbiology Arrives in America, 1878–1899

Microbiology gained a foothold in the United States after the discoveries of European researchers Ferdinand Cohn (1828–1898), Louis Pasteur (1822–1895), and Robert Koch(1843–1910) during the 1870s and early 1880s. While American physicians and biologists followed developments in the germ theory of disease (and the germ theory of fermentations) with great interest, few conducting original studies of their own. One exception was Thomas J. Burrill (1839–1916), a botanist and plant pathologist at the University of Illinois, who identified the etiological agent of pear blight in 1878. Burrill's discovery spawned little interest in bacteria as plant pathogens. Instead, microbiology first appeared in departments of pathology and veterinary medicine. William H. Welch (1850–1934), T. Mitchell Prudden (1894–1924), and Harold C. Ernst (1856–1922) each studied in Europe during the late 1870s, returning to the United States to begin instruction at Bellevue Medical College, Columbia University College of Physicians and Surgeons, Harvard, and Johns Hopkins University. By close of the nineteenth century, more than fifty American medical colleges required formal instruction in bacteriology, mostly intended to impart the techniques for isolating the pathogens responsible for tuberculosis, cholera, diphtheria, anthrax, plague, typhoid fever, and gonorrhea. While American medical colleges actively promoted bacteriological instruction, only William Welch's discovery of the gas-gangrene bacillus (1892) drew attention from European bacteriologists. Instead, American bacteriologists distinguished themselves in their contributions to public health practice and sanitary science.

In response to the global cholera epidemic of 1892, the New York City Health Department founded the first extensive laboratory for public health bacteriology. Under the direction of Hermann M. Biggs (1859–1923), William H. Park (1863–1939), and Anna W. Williams (1863– 1954), the department, in 1894, designed and distributed throat culture kits for diagnosing cases of diphtheria. The next year, Park and Williams refined methods of mass-producing diphtheria antitoxin, supplying it without charge to city physicians, and selling to outside public health departments. By 1899, more than twenty state and city departments of health established similar laboratories, aiding in the diagnoses of tuberculosis, typhoid fever, malaria, and gonorrhea.

Microbiologists also supported the field of sanitary science, helping to eliminate harmful microbes from drinking water, milk, and food. At Massachusetts Institute of Technology and the Lawrence Experiment Station, William T. Sedgwick (1855–1921) and his students designed methods of improving water filtration systems, reducing rates of typhoid fever in American cities by more than 70 percent. Sedgwick's colleagues, Samuel C. Prescott (1872– 1962) and William L. Underwood (1864–1929), studied means of reducing food poisoning in commercially manufactured foods.

American microbiologists achieved their greatest successes in the fields of veterinary medicine, dairying, soil science, and plant pathology, under the aegis of the bureaus of the U.S. Department of Agriculture and the several state agricultural experiment stations. At the Bureau of Animal Industry, Daniel E. Salmon (1850–1914) and Theobald Smith (1859–1934) isolated the bacterial agent of swine plague, and developed the first heat-killed (as opposed to Pasteur's live-attenuated) vaccine. In the early 1890s, Salmon and Smith identified the protozoan responsible for Texas cattle fever, and established that a tick carried the parasite from host to host, the first demonstration of an insect vector in the spread of disease. In the field of dairying, Herbert W. Conn (1859–1917) at the Storrs Agricultural Experiment Station and Harry L. Russell (1866–1954) at the Wisconsin station detailed the function of bacteria in the formation and flavoring of hard cheeses and butter. In the late 1890s, researchers at the New Jersey and Delaware stations advanced the scientific understanding of soil fertility, defining the role of bacteria and fungi in the decomposition of manures, their action upon fertilizers, and their importance in the fixation of atomospheric nitrogen. American plant pathologists, in the 1880s and 1890s, contributed greatly to the understanding and prevention of various wilts, rusts, and blights of agricultural crops. While most plant diseases are fungal in origin, Erwin F. Smith(1854–1927), of the Bureau of Plant Industry, and Harry Russell were the first to identify bacterial diseases of plants.

The Flourishing of American Microbiology, 1900–1924

Microbiology flourished in the first quarter of the twentieth century. The Society of American Bacteriologists and the Laboratory Section of the American Public Health Association formed in 1899. In the first years of the new century, the Rockefeller Institute for Medical Research in New York, the John McCormick Institute in Chicago, and the U.S. Public Health Service Hygienic Laboratory began sponsoring original investigations in medical microbiology. By 1925, American researchers could point to notable advances in the comprehension and control of many infectious diseases, including: Walter Reed (1851– 1902) and James Carroll (1854–1907) for demonstrating that mosquitoes transmitted yellow fever; Simon Flexner (1863–1946) for his discovery of a new variant of dysentery and devising a serum for treating meningitis; Howard T. Ricketts (1871–1910) for his research on Rocky Mountain spotted fever; George W. McCoy (1876–1952) and William B. Wherry (1875–1936) for identifying the bacteria of tularemia; and, F. Peyton Rous (1879–1970) for proposing a viral etiology of some cancers.

In the field of public health, bacteriology occupied an authoritative position. Increasingly, public health leaders shifted their focus from cleanup campaigns and municipal reforms to the bacteriological methods of identifying sick or susceptible individuals, including the control of "health carriers." In 1907, the New York City Health Department detained the immigrant cook Mary Mallon ("Typhoid Mary") for transmitting typhoid fever, even though she showed no signs of the illness herself. Health officials also lobbied for compulsory school vaccinations and mandatory tests for susceptibility to diphtheria and scarlet fever. By 1925, most municipalities distributed filtered or chlorinated water, mandated pasteurized milk, and inspected commercial canneries.

Veterinary microbiologists devised diagnostic tests, vaccines, and treatments for several economically devastating livestock diseases (e.g., hog cholera, blackleg in sheep, pullorum in chickens, and blackhead in turkeys). Regarding bovine tuberculosis and contagious abortion in cattle, these efforts carried implications for human health. In the first years of the new century, Theobald Smith, Harry Russell, and Mazyck P. Ravenel (1861–1946) documented that the dairy products made from tubercular cows could transmit the disease to infants. Similarly, Alice C. Evans (1881–1975) argued, in 1916, that cows suffering from contagious abortion could transmit undulant fever to humans. While Evans's claim drew initial skepticism, her work led to the recognition of a new class of infections, brucellosis. As a result, the Bureau of Animal Industry sponsored a national eradication movement, dramatically decreasing the incidence of both diseases.

The Triumph of Microbiology, 1925–1979

Throughout much of the twentieth century, American microbiologists led an age of scientific triumph. In the battle against infectious disease, researchers and pharmaceutical firms improved vaccines and therapeutic sera to control measles, diphtheria, mumps, rubella, and whooping cough. At Vanderbilt University and the Rockefeller Institute, Ernest W. Goodpasture (1886–1960), Thomas M. Rivers (1888–1962), and Richard E. Shope (1901– 1966) transformed the study of influenza, herpes, and encephalitis, developing methods of culturing these viruses in chick embryos. John F. Enders (1897–1985) and his colleagues at Harvard University devised a technique in 1949 for growing polio virus in cultures of tissue cells. With in a decade, Jonas E. Salk (1914–1995) and Albert B. Sabin (1906–1993) introduced two separate polio vaccines, largely eliminating the scourge of infantile paralysis. While penicillin was introduced as a therapeutic agent in the early 1940s by the British researchers Alexander Fleming, Howard Florey, and Ernst Chain, American scientists also studied the antagonisms between different microbes. In 1939, Rockefeller Institute researcher René Dubos (1901–1981) isolated a crystalline antibiotic, gramicidin, from a soil organism. Unfortunately, gramicidin proved too toxic for internal use. Dubos's former teacher, Selman Waksman (1888–1973), found another group of soil organisms showing anti-germicidal properties. Waksman and his students at Rutgers University identified streptomycin, the first effective antibiotic in the treatment of tuberculosis.

Microbiologists equally contributed to the development of molecular biology. In the 1930s and 1940s, Oswald T. Avery (1877–1955) and his colleagues at the Rockefeller Institute showed that DNA played a role in transforming non-virulent pneumococci into virulent forms, intimating that this substance might be generally involved in heredity. Employing a bacteriophage of E. coli, Max Delbruck (1906–1981) and Salvador Luria (1912– 1991) revealed that bacteria and viruses followed normal principles of replication and mutation, there by establishing phage as a model organism for genetic research. Joshua Lederberg (1925–) and Edward L. Tatum (1909– 1975) showed that bacteria can exchange genes when cultured in direct contact. In 1952, Lederberg and Norton D. Zinder (1928–) elucidated the phenomenon of bacterial transduction, where a phage carries DNA from one bacterium to another. Their research suggested a mechanism for introducing genes into new cells, a technique now common in genetic engineering. In the 1960s and early 1970s, Matthew S. Meselson (1930–), David Baltimore (1938–), and Howard M. Temin (1934–1994) employed bacteriophages and other viruses to delineate the relationship among DNA, RNA, and protein synthesis.

Emerging Challenges, 1980–2002

In 1979, the World Health Organization declared that one of the most ancient and devastating diseases, smallpox, had been officially eliminated. Scientific optimism proved, however, to be short-lived, as medical researchers soon grappled with the emergence of AIDS. While Robert C. Gallo (1937–), of the National Institutes of Health, co-discovered the human immunodeficiency virus in 1983, and developed an accurate test for HIV infection, no vaccine or cure has been found. Microbiologists have also struggled against new microbial threats, from Rift Valley fever, dengue fever, ebola, and hanta virus abroad, to lyme disease and multiple-drug resistant tuberculosis domestically. Even the class of infectious agents has expanded. In 1982, Stanley Prusiner (1942–) found evidence of infectious protein particles or "prions," and concluded that they were responsible for scrapie, a transmissible spongiform encephalopathy fatal to sheep. In the 1990s, Prusiner and others demonstrated that both mad cow disease in livestock and Creutzfeldt-Jakob disease in humans were likely caused by prions.