Studies on the effects of radiation on microorganisms. (2)

On the relative sensitivity to ultraviolet light of several microorganisms, as determined by fluorescent photometer

Abstract

In the present paper, the writer reported the result of investigations of the effect of ultraviolet light on several microorganisms. The sensitivity of the microorganisms to ultraviolet light decreased in the following descending order: Staphylococcus aureus>Serratia marcescens>Escherichia coli>Xanthomonas pruni>Sarcina sp.>Botrytis cinerea.
The pigment formation in cells of Serratia marcescens has some influence to the sensitivity, a pigmentless strain being more sensitive to ultraviolet light than a pigment-producing strain (carmine strain). Judging from the survival curves of the two strains, the cells of the pigment-producing strain appear to contain larger amount of ultraviolet-absorbing substances than the cells of the pigmentless strain.
Comparisons of the irradiation dose were made on the basis of irradiation energy expressed by (light intensity irradiation time), but there was a tendency that a short irradiation with high intensity of light was more effective than a long irradiation with low intensity, even if the total irradiation energy calculated with the above formula was kept constant.