Irradiation of Plant Viruses and of Microörganisms with Monochromatic Light

Abstract

I. The physical installation included, for most of the work, a fused quartz monochromator and an intense source of radiation provided by a capillary mercury vapor lamp. Special attention was given to the development of a suspension technique giving reproducible results and to a method whereby the virus and the bacteria might be satisfactorily irradiated simultaneously and in the same suspension. Exposures were made in a fused quartz cell (with stirring) in a water-ice bath (1-2[degree] C). The exposure suspension consisted of (a) semipurified virus, and (b) bacteria taken during the logarithmic growth phase from a bouillon culture. Poured plates (agar) were made in dilution series for the bacterial counts, and inactivation of the virus was determined by the incidence of disease when inoculated into tobacco plants, comparing irradiated material with otherwise similarly treated controls. Between the limits investigated, [lambda]2537 and 6120A, the greatest influence was at [lambda]2652A and, in general, the energy values representing 100% killing of the bacteria were far below the values having any measurable effect on the virus.[long dash]II. A crystalline quartz monochromator and a new form of exposure-cell, with stirrer, designed for suspension technique, were employed. In resistance toward ultra-violet radiation the virus of typical tobacco mosaic was compared with vegetative forms of Serratia marcescens and Bacillus subtilis and with spore forms of B. subtilis and B. megatherium. Survivor curves are given for 7 different wave lengths from 2537 to 3652A. While the curves for vegetative and spore stages of the bacteria are conformable, the level of energies required to give a particular survivor value is somewhat greater for the spores, and at any lethal wave length the resistance of spores of B. megatherium is greater than that of B. subtilis. The resistance of the virus irradiated coincidently and in the same suspension with the bacteria is so much greater than spore stages as to be of a different order of magnitude. In general, the maximum lethal effect was at [lambda]2652A, although, according to these data, B. megatherium (spores) exhibits greater sensitivity at [lambda]2804A. There is little relation between heat resistance and resistance toward ultra-violet radiation.