June 29, 1935 (a Saturday)

On this date, Wendell Meredith Stanley announced the isolation of tobacco mosaic virus (TMV) as a crystalline molecule in the journal Science. For this feat, he later was a co-recipient of the Nobel Prize in Chemistry for 1946.

Stanley’s work had great significance for the ongoing debate about the scientific distinction between life and non-life. In 1937 Barclay Moon Newman noted that, “It has astonished the scientific world that a single molecule can be the causative organism of a disease. How can a crystal be made up of living molecules?” Stanley said in his Nobel Prize Lecture on 12 December 1946:

Reproduction, mutation and metabolic activity have long been regarded as unique and special properties of living organisms. When viruses were found to possess the ability to reproduce and to mutate, there was a definite tendency to regard them as very small living organisms, despite the fact that the question of metabolic activity remained unanswered. Because of their small size they could not be seen by means of the ordinary light microscope. Although. this fact puzzled some investigators, it was pushed aside and for over thirty years interest in virus research was centered about the discovery of new viruses and on studies of the pathological manifestations of viruses.

Then, around 1930, Elford… demonstrated that different viruses possessed different and characteristic sizes, and that some viruses
were as large as about 300 mμ, whereas others were as small as 10 mμ… The fact that, with respect to size, the viruses overlapped with the organisms of the biologist at one extreme and with the molecules of the chemist at the other extreme only served to heighten the mystery regarding the nature of viruses. Then too, it became obvious that a sharp line dividing living from non-living things could not be drawn and this fact served to add fuel for discussion of the age-old question of “What is life?”.

(…)

Needless to say, for a time there was great skepticism that the crystalline material could be tobacco mosaic, due chiefly to the old idea that viruses were living organisms… As a whole, the results indicated that the crystalline material was, in fact, tobacco mosaic virus.

Stanley did not realize the importance of the nucleic acid component of TMV. Viruses today are recognized to be literally “parasitic” chemicals, segments of DNA or RNA wrapped in a protein coat. They can reproduce within cells, often with disastrous results to the host organism, but they cannot reproduce on their own, which is why they are not considered alive by biologists. Earlier ideas that viruses represent a kind of halfway point between life and non-life have largely been abandoned. Instead, viruses are now viewed as detached fragments of the genomes of organisms due to the high degree of similarity found among some viral and eukaryotic genes.

Stanley co-authored the book Viruses and the Nature of Life (1961).

References:

• Angela N. H. Creager. The Life of a Virus: Tobacco Mosaic Virus as an Experimental Model, 1930-1965 (Chicago, IL: University of Chicago Press, 2002) p. 47.
• Wendell Stanley, “Isolation of a crystalline protein possessing the properties of tobacco-mosaic virus” Science, vol. 81, issue 2113: 644-645 (1935).
• Wendell Stanley and Evans G. Valens. Viruses and the Nature of Life (New York: Dutton, 1961).