Experimental Correspondence between Spore Dosimetry and Spectral Photometry of Solar Ultraviolet Radiation

Abstract

The biologically effective dose of solar UV radiation was estimated from the inactivation of UV-sensitive Bacillus subtilis spores. Two types of independent measurements were carried out concurrently at the Aerological Observatory in Tsukuba: one was the direct measurement of colony-forming survival that provided the inactivation dose per minute (ID/min) and the other was the measurement of the spectral irradiance by a Brewer spectrophotometer. To obtain the effective spectrum, the irradiance for each 1 nm wavelenght interval from 290 to 400 nm was multiplied with the efficiency for inactivation derived from the inactivation action spectrum of identically prepared spore samples. Integration of the effective spectrum provided the estimate for ID/min. The observed values of ID/min were closely concordant with the calculated values for the data obtained in four afternoons in 1993. The average ratio (+/- SD) between them was 1.24 (+/- 0.16) for 14 data points showing high inactivation rates (> 0.05 ID/min). Considering difficulties in the absolute dosimetry of UV radiation, the concordance was satisfactory and improved credibility of the two types of monitoring systems of biologically effective dose of solar UV radiation.

Resistance ofBacillusEndospores to Extreme Terrestrial and Extraterrestrial Environments

“…Using a series of cutoff filters, two independent studies have concluded that the most effective portion of the solar spectrum for inactivation of spore dosimeters consisted of UV-B radiation in the 305-to 325-nm range (117,217). A recent experiment simultaneously compared the response of the spore dosimeter with that of a Brewer sunlight spectrophotometer at the same location and over the same time periods and found good correlation between the two methods, indicating that the spore dosimetric system was indeed a relevant method for monitoring biologically active solar UV (123).…”

“…An increased UV-B level of solar radiation will have many harmful effects on the biosphere and on human health (229). A quantitative assessment of the implications of progressive ozone depletion for life on Earth has been attempted theoretically, by applying radiative transfer models for different total ozone columns, where the resulting solar spectrum is weighted with biological action spectra (96), or attempting to correlate the inactivation rate of biological dosimeters exposed to sunlight with simultaneous measurements of ozone column thickness and spectral irradiance (120,123,159), or experimentally by applying UV radiation suitable for the simulation of a certain degree of ozone depletion (14). Solar UV dosimetry based on spore inactivation is probably the most sensitive measure of the change in the ozone concentration because of the high relative sensitivity to the shorter-wavelength portion of solar spectrum.…”

Bacillus subtilis spore film dosimeters in personal dosimetry for occupational solar ultraviolet exposure

“…A Japanese group found a good correlation between spectral irradiance of solar irradiation and the inactivation of UV-sensitive Bacillus subtilis spores (TKJ6321) [34,35]. The spores had been ®xed on a membrane and attached to a slide mount or cardboard to measure ambient UV radiation and personal UV exposure [36].…”

Dosimetria esporular: Bacillus subtilis TKJ6312 como biossensor de radiação solar biologicamente ativa

“…O dosímetro de esporos tem sido preparado no Laboratório de Ciência da Vida da Faculdade de Ciências da Universidade Rikkyo, Tóquio, Japão, onde os esporos da cepa mutante de Bacillus subtilis TKJ6312 são misturados com 0,6% (m/v) de agarose. 15 Quatro alíquotas de 5 µL dessa suspensão, cada uma contendo aproximadamente 10 6 esporos são adicionadas sobre um filtro de membrana e dispostos em slides. Em seguida, uma amostra é coberta com cartão (controle).…”