Bawden, Frederick Charles
BAWDEN, FREDERICK CHARLES
(b. North Tawton, Devon, England, 18 August 1908; d. Rothamsted, England, 8 February 1972)
plant pathology, biochemical virology.
Bawden was the son of George Bawden and Ellen Balment, both of whom supervised a Poor Law institution (a workhouse) in Okehampton during much of his youth. It has been suggested that his early experiences helped to develop a continuing concern for the human condition. The large garden of the institution is presumed to have evoked an interest in agriculture in general, and in the growth of potatoes in particular. Bawden studied botany at the Okehampton Grammar School and some chemistry at the Crediton Grammar School, after which he entered Cambridge as a scholarship student. He has been described as sports loving, cheerful, and active in the social life of his college. As a senior scholar at Emmanuel College, he worked with Frederick T. Brooks on cereal rusts, the subject of his M.A. thesis (1930) for the diploma in agricultural science. Fungus infections were the subject of many of his later writings.
In 1927, Redcliffe N. Salaman established the Potato Virus Research Station at Cambridge with Kenneth M. Smith as senior research assistant. In the summer of 1930, Bawden was appointed an assistant in the poorly equipped station and began work on the potato and its viruses. In this period he was concerned with the detection of virus infection and developed a long term interest in serology.
The year 1934 was important for Bawden. On 6 September he married Marjorie Elizabeth Cudmore, who had been a fellow student at both Okehampton and Cambridge; they had two sons. He also began a long collaboration with the biochemist Norman W. Pirie, who had been woiking in the department of pathology, where Bawden was learning serological technique with E. T. C. Spooner. Pirie and Bawden attempted to isolate the potato virus— a virus difficult to purify—and in 1936 reported the association of its infectivity with material sensitive to various proteinases. Their enthusiasm was heightened by the 1935 report of Wendell M. Stanley at the Rockefeller Institute, who had described the isolation and crystallization of the virus of the tobacco mosaic disease.
In 1936 Bawden moved to the Rothamsted Experimental Station in Hertfordshire as virus physiologist in the department of plant pathology, a position that permitted him to work with viruses other than those of potatoes. He continued his collaboration with Pirie at Cambridge. By the end of 1936, they were able to confirm, correct, and extend Stanley’s report, In the next five years, the two men made many exciting discoveries of the properties of numerous plant viruses, and Pirie moved to Rothamsted in 1940. Bawden became head of his department in 1940 and director of the station from 1958 until his death.
The station, which celebrated its centenary in 1943, was for its first fifty years a site of closely monitored field experiments on the effects of fertilizers on plant growth, Supported from 1911 by a governmental development fund for the rehabilitation of British farming, the station thenceforth became a leading agency for agricultural research in England and for the development of world agriculture. This role was bolstered by the work of Bawden and his associates in plant virology and pathology. The growth of the station under his directorship was facilitated by his visible and lasting concern for the improvement of British agriculture and food production during World War II and afterward. He wrote numerous articles on problems of agriculture, attempting to communicate with the general public. His major scientific and administrative contributions established his national and international prestige. He was elected to the Royal Society in 1949 and was given many awards and responsibilities.
The distinction between nonfilteruble bacteria and the filterable tobacco mosaic virus had been established by Dmitrii I. Ivanovskii and Martinus W. Beijerinck in 1892 and 1898, respectively, and these results pointed to the possible existence of very small noncellular pathogens, a conclusion affirmed by the development of more sophisticated filtration techniques. By the mid 1930’s an extensive body of work had appeared on the properties of tobacco mosaic virus and on efforts to purify it from the sap of infected plants. The startling work of Stanley, based on the advances of the previous decade in protein isolation, required rapid confirmation. This was soon provided by Bawden and Pirie.
Their first paper on this subject, published in 1936 with the X-ray crystallographers John D. Bernal and Isidor Fankuchen, also described the isolation of crystallizable infectious nucleoproteins from tobacco and tomato plants infected with several distinctive strains of tobacco mosaic virus. Each virus preparation reproduced the characteristic disease in suitable plants. The authors emphasized that the small needles obtained should be described as “liquid crystalline,” possessing only two-dimensional regularity. Bernal and Fankuchen later described these needles as “tactoids,” When they were sufficiently purified, concentrated preparations spontaneously separated into a liquid crystalline birefringent lower layer and an upper layer showing anisotropy of flow as a result of the alignment of soluble viral particles.
The soluble rods were readily sedimented, and I he dried pellets, crystals, or oriented liquid layers were easily examined by X-ray crystallography. The preparations were shown to contain rods of constant diameter aligned in close-packed hexagonal array. Therods were comprised of small, identical protein subunits along their length, but it was not clear that the rods were of identical length. The crystallographic data were similar to those Ralph W. G. Wyckoff and Robert B. Corey obtained earlier on Stanley’s material establishing the virtual identity of the virus preparation obtained by the two laboratories.
The English preparations possessed nitrogen contents more characteristic to proteins than did the nitrogen content reported initially by Stanley; but more important, for the first time the virus was found to contain phosphorus and carbohydrate within a nucleate of the ribose type (RNA), isolable alter disruption of the virus. Bawden and Pirie soon demonstrated the presence of RNA in numerous other plant viruses. At about this time Max Schlesinger, working in London, found that preparations of bacteriophages contained a nucleate of the deoxyribose type (DNA). In the next decades many other viruses infecting plants, animals, and microbes were also found to carry a nucleate of either RNA or DNA. which was proved by the early and mid 1950’s to determine the genetic continuity and capacity for duplicability of the particular virus. In the 1970’s some infectious diseases were found to be caused by a “viroid,” a small, stable infectious nucleate of the ribose type, devoid of protective protein. In the mid 1980’s it was reported that the etiologic agents of a few difficult-to-study animal and human diseases are free of nucleic acid and consist largely of protein. The unequivocal proof of the existence of such agents, termed “prions,” has been difficult to establish.
In their early papers and for decades thereafter, Bawden and Pirie were concerned with the rigor of the evidence that the infectious tobacco mosaic virus could be described as a nucleoprotein rod of a single length, and that the particles isolated were present as such in infected sap. They had shown that the conditions of purification facilitated aggregation. In subsequent years it was shown, mainly in Stanley’s laboratory, that the infectivity and distinctive monomelic rods possessed essentially identical sedimentation constants in an analytical ultracentrifuge, that older infected plants contained an increased percentage of end-to end dimers, and that the preparation of viruses for visualization in the electron microscope led to breakage of the rods. It is now generally believed, consistent with the known internal position of the single genetic element (RNA, lengthwise within the viral rod), that the tobacco mosaic virus must be of a distinctive length, within very narrow limits.
In 1938 the tomato bushy stunt virus was found by Bawden and Pirie to give rise to true three-dimensional isotropic crystals comprised of essentially spherical nucleoprotein particles. These properties and the sedimentation pattern of the virus very early suggested an identity of the infectious virus and the crystallizable spherical particle. Indeed, in 1942 Max Lauffr determined the size distribution function of a virus preparation by studying the diffusion of sedimenting particles and demonstrated that the diameters of the particles could not deviate from the mean by more than I percent.
The enlarging study of viruses isolated from various diseased plants revealed many new biological phenomena. Some of these new phenomena were facilitated by Bawden’s skills in serology. For example, although the tobacco mosaic virus and cucumber viruses 3 and 4 do not have any common hosts, the virus preparations were similarly liquid crystalline. Antisera prepared against each gave significant serological cross sections that were evidence of the previously unsuspected relatedness of the proteins of the respective infectious entities.
In another group of investigations, various tobacco necrosis viruses were proved to be serologically unrelated. One isolate, derived from a single necrotic lesion and massive infection of leaves purified by Pirie and his collaborators, was found to consist of two fractions of noninterconvertible viruses of different sizes. Bawden showed these to be serologically unrelated In 1960 one of these complex viral systems was shown, by Basil Kassanis and H. L. Nixon at Rothamsted, to lead to the production of two nucleoproteins of different sizes. These consisted to an infectious viral nucleoprotein of fairly large size and a smaller noninfectious nucleoprotein; the latter multiplied only in the presence of the former. These observations led to the recognition of dependent satellite viruses. The discovery of this phenomenon facilitated the dissection of numerous mullicomponent virus systems in which virus particles containing different RNA components were unable to multiply unless all of the RNA components were present.
Although Bawden and Pirie had discovered RNA in the plant viruses by 1936, they did not undertake characterization of its physical properties or testing the biological activity of this material before 1956, focusing instead on the possibly crucial roles of the viral proteins. After the initial reports of the infectivity of the RNA of tobacco mosaic virus in 1956, they showed that their early methods of disrupting the virus permitted the isolation of infectious material. Despite the roles of ribonucleases in destroying the infectivity, the very low efficiency of infection by viral RNA prevented Bawden and Pirie’s unequivocal acceptance of the RNA alone as the agent of infectious heredity. Bawden’s last experimental papers, written with Pirie in 1972, were on the problems of isolating infectious viral nucleic acid directly from infected leaves.
Bawden wrote numerous reviews on virus disease as well as the text Plant Viruses and Virus Diseases (1939), He participated in many symposia, including some on virus multiplication, a subject that made important advances in the postwar period. His papers and discussions demonstrate a clear understanding of the centrality of the infected cell and the crucial use of such stripped-down biological materials in the study of the multiplication of bacterial and animal viruses. Nevertheless, work on similar systems of infected plant cells did not develop at Rothamsted during his tenure. His former collaborator Kassanis began such work there in 1972.
Despite Bawden’s interest in the development of academic virology and his continuing research activities, his major concerns and achievements after World War II were related to improvements in agricultural science and technique, He supported measures and studies for the control of infectious disease in England, Bawden was very pleased with the results achieved at Rothamsted in the late 1950’s and 1960’s in the development of the virus-free, high-yielding potato stocks now used widely in that country.
Bawden received the Research Medal of the Royal Agricultural Society in 1955 and was president of the Society for General Microbiology in the year 1959–1960. He visited many developing countries to advise on agricultural problems and served as chairman of the Agricultural Research Council of Central Africa from 1964 to 1967. He was knighted in 1967 and in the following year served as president of the First International Congress of Plant Pathology.
Bawden believed it is not possible to distinguish sharply between basic and applied research in agriculture. In a 1972 article in Nature, writing as director of the station and as senior member of the Agricultural Research Council, he objected bitterly to proposals that long-term agricultural research be supported by contractual arrangements with a government ministry. Unfortunately, he died of heart disease before he could bring his ideas and personality to bear decisively on this important problem of scientific policy.
BIBLIOGRAPHY
I. Original Works. All of Bawden’s publications are listed chronologically in an article by N. W. Pine in Biographical Memoirs of Fellows of the Royal Society, 19 (1973), Key publications include “Experiments on the Chemical Behaviour of Potato Virus’ X,” in British Journal of Experimental Pathology, 17 (1936), 19–63, with N. W. Pirie; “Liquid Crystalline Substances from Virus-Infected Plants,” in Nature, 138 (1936), 1051–1052, with N. W. Pirie, J. D. Bernal, and I. Fankuchen; “The Isolation and Some Properties of Liquid Crystalline Substances from Solanaceous Plants Infected with Three Strains of Tobacco Mosaic Virus,” in Proceedings of the Royal Soviety of London, B 123 (1937), 274–320, with N. W. Pirie; “The Relationships Between Liquid Crystalline Preparations of Cucumber Viruses 3 and 4 and Strains of Tobacco Mosaic Virus,” in British Journal of Experimental Pathology, 18 (1937), 275–291, with N. W. Pirie; “Crystalline Preparations of Tomato Bushy Stunt Virus,” ibid., 19 (1938), 251–263, with N. W. Pirie; “The Serological Reactions of Viruses Causing Tobacco Necrosis,” ibid., 22 (1941), 59–70; Plant Viruses and Virus Diseases (Leiden, 1939; 4th ed., New York, 1964); “The Separation and Properties of Tobacco Mosaic Virus in Different States of Aggregation,” in British Journal of Experimental Pathology, 26 (1945), 294–312, with N. W. Pirie; “Studies on the Importance and Control of Potato Virus X,” in Annals of Applied Biology, 35 (1948), 250–265, with B. Kassanis and F. M. Roberts; “Virus Multiplication Considered as a Form of Protein Synthesis,” in The Nature of Virus Multiplication: Symposium of the Society for General Microbiology, II (Cambridge, 1953), 21–45, with N. W. Pirie; “Physiology of Virus Diseases,” in Annual Review of Plant Physiology, 10 (1959), 239–256; “The Infectivity and Inactivation of Nucleic Acid Preparations from Tobacco Mosaic Virus,” in Journal of General Microbiology, 21 (1959), 438–456, with N. W. Pirie; “Bringing Rothschild Down to Earth,” in Nature, 235 (1972), 7; and “The Inhibition, Inactivation and Precipitation of Tobacco Mosaic Virus Nucleic Acid by Components of Leaf Extracts,” in Proceedings of the Royal Society of London, B 182 (1972), 319–329, with N. W. Pirie.
II. Secondaty Literature. Geoffrey C. Ainsworth, Introduction to the History of Plant Pathology (Cambridge, 1981); Theodore O. Diener, Viroids and Viroid Diseases (New York, 1979); Joseph S. Fruton, Molecules and Life (New York, 1972); Max A. Lauffer, “Contributions of Early Research on Tobacco Mosaic Virus,” in Trends in Biochemical Science, 9 (1984), 369–371; and A. P. Waterson and Lise Wilkinson, An Introduction to the History of Virology (New York and Cambridge, 1978).
Seymour S. Cohen