Karen-Beth G. Scholthof
Texas A&M University
One
hundred years ago, Martinus W. Beijerinck, a Professor of Microbiology
at the Technical University at Delft, the Netherlands, put forth his concepts
that viruses were small and infectious. He defined the infectious agent
as a "contagium vivum fluidum", after he discovered that the virus readily
passed through a porcelain filter, suggesting that it was smaller than
bacteria. He also observed that the 'agent' could diffuse through agar
that retained bacteria, and furthermore, that the virus could not be cultured
except in living, growing plants. The virus was tobacco mosaic virus
(TMV). This report, suggesting that 'microbes' need not be cellular, was
to forever change the definition of pathogens. In 1898, two Germans,
Loeffler and Frosch, former students of Koch, also used a porcelain filter
for the isolation of the causal agent of foot and mouth disease of cattle,
but they suggested that it was a very small microbe. Beijerinck was almost
alone in his forward thinking conclusions that he had a filterable, invisible
infectious agent that differed from small microbes. In fact, it took
50 years to prove that TMV 
was
an infectious nucleoprotein. In that time, TMV was the first virus
to be purified in pure crystal form, the first pathogen to be passed through
filter candles, and the first virus to be identified as composed of an
infectious nucleic acid. Since then many viruses have been discovered in
plants, animal, fungi, and bacteria. TMV would continue to play a leading
role in the development of fundamental concepts in virology. In the 1960s
and 1970s, TMV was a key component in the shift to molecular work in viruses,
particularly with regard to the understanding of genetic information and
the biological role of virus encoded proteins.
The history of TMV roughly parallels the early history of the American Phytopathological Society (APS) that was founded in 1908 and celebrates its 90th anniversary this year. At the 50th anniversary meeting of APS, W. M. Stanley (APS member, Nobel prize 1946 for crystallization of TMV) commented that the papers on TMV "demonstrate in no uncertain terms the great debt that the field of general virology owes to plant virus research" (1). At this same meeting, J. G. Horsfall stated: "The tobacco mosaic virus is leading us and will surely lead us further into a knowledge of what life itself really is."
As part of the celebration of a century of virology, a TMV Symposium will precede the 7th International Congress on Plant Pathology. To round out this celebration of the 100th anniversary of virology, links are provided to M. Beijerinck's report on tobacco mosaic virus and a historical view of the discovery of tobacco mosaic virus by Mayer, Ivanowski, and Beijerinck is provided by Dr. Milton Zaitlin.
(1). Plant Pathology: Problems and Progress, 1908-1958. (1959). Eds: C. S. Holton, G. W. Fischer, R. W. Fulton, H. Hart, and S. E. A. McCallan. University of Wisconsin Press.