Abstract
In the present paper some experiments are described on the effect of ultraviolet radiation upon the pathogenicity and antigenicity of tobacco mosaic virus (TMV).
The virus preparation used in this work was the aqueous suspension of TMV which had been purified by Bawden's procedure. The antiserum used was prepared by injecting rabbits with the purified TMV. The infectivity of the irradiated TMV was tested by the so-called half-leaf method on the leaves of Nicotiana glutinosa plants. In serological tests of TMV, the precipitin reaction was used. The virus preparation 2-3mm thick in a Petri dish of 9cm in diameter on a shaking apparatus was irradiated by means of the Matsuda's 15-W germicidal lamp. The wave-length of the ultraviolet light employed was 2537 Å. The pH of the virus preparations were 6.0-6.2 and their temperatures were 15°-20°C at the time of irradiation, and no rising of temperature of the prepations due to the irradiation was recognized.
The experimental results are summarized as followes:
(1) When the logarithm of the surviving fraction has been plotted against the dose of irradiation according to the numder of lesions obtained by the half-leaf method of inoculation, the survival curves were shown by straight lines with the small difference due to the experimental error (Fig. 1 and 2). Consequently, these results seem to agree with the view that the inactivation of virus by ultraviolet light is caused by the absorption of asingle ultraviolet quantum in the same way as that the inactivation of virus by ionizing radiations is attributable to a single ioization of the virus.
(2) The inactivation doses (the 37% doses) were estimated from the survival curves to be 2.5×103μW and 1.5×103μW in the case of the virus preparations of 0.2% and 0.02%, respectively.
(3) The preparations of TMV completely inactivated by ultraviolet irradiations always showed as strong serological activity as the control (Table 1, 2, 3 and 4). However, the serological activity was completely lost when the doses of ultraviolet radiations were increased to more than 13×105μW, while the precipitin reaction of TMV irradiated with the doses of 2.6-6.5×105μW became intensifid as compared with the control (Table 5).
