The Physical and Chemical Properties of a Distinctive Strain of Tobacco Mosaic Virus

It has been apparent for some time in both plant and animal virus diseases that the extent and type of the disease produced in a particular host may vary widely according to the strain of virus involved, and that members of the same virus family may range in pathogenicity from a strain which is quite innocuous to one which is definitely lethal. These facts make it of unusual interest to elucidate the nature of the chemical differences in the structure of a virus which are responsible for such variations in the biological properties. The nucleoproteins of the tobacco mosaic virus family are particularly suitable for such a study, for in many cases they can be obtained in comparatively large amounts and in a degree of purity superior to that of most other plant and animal viruses. At this stage in the investigation of chemical differences between strains, the variants which differ most widely from the type strain with respect to biological properties seem to offer the best opportunity for demonstrating structural differences. Recently, Dr. Holmes isolated from rib-grass (Plantago lanceolata L.) a strain of tobacco mosaic virus which possesses unique properties and which can be easily distinguished from previously known strains by its ability to form necrotic ring lesions in Turkish tobacco, by its adaptation to rib-grass, and by its failure to produce local lesions in bean plants (Phaseolus vulgaris L.) (1). This unusual variant was shown beyond reasonable doubt to be a strain of tobacco mosaic virus by its ability to withstand heat and desiccation, by its inability to infect tobacco plants diseased with typical tobacco mosaic virus, by its precipitation with tobacco mosaic virus antiserum, and by the nature of its response to the genie constitution of tobacco plants. The present communication deals with the isolation and purification of the new virus and with the examination of some of its physical, chemical, and serological properties. Preparation of the Virus-Young Turkish tobacco plants were inoculated with the rib-grass virus by rubbing one or two leaves on each plant with a gauze pad saturated with infective juice. This juice was obtained from a tobacco plant showing the typical symptoms of disease described by Holmes (1). About a month after inoculation, the plants were harvested and frozen. The virus was subsequently extracted from the macerated plant