A Biofilm Used as Ultraviolet‐dosimeter

Abstract

Abstract— A UV‐dosimeter has been developed for routine measurements which mainly weights the various components of the spectrum in relation to their damaging effects on a microorganism. For this purpose a biofilm was constructed, comprising dried spores of Bacillus subtilis (wild‐type or DNA repair defective strain), immobilized on transparent polyester plastic sheets. After irradiation, the biofilm was incubated in a growth medium. The proteins, synthesized by the immobilized microorganisms after spore germination and several cell divisions, were stained and determined by photometry, giving a measure of the biological activity. The ”biologically effective dose“ was determined from a calibration curve. It reflects the dose equivalent to that of the calibration source producing the same effect. The UV‐response of the biofilm is additive and follows the reciprocity law in the range of fluence rates investigated. The response is nearly independent of temperature within the range of ‐20°C to +70°C as well as of humidity between about 37 and 80% relative humidity. Storage for up to 9 months at <70% relative humidity and room temperature does not significantly influence the viability of the spores.

Oxidative stress and enzymatic scavenging of superoxide radicals induced by solar UV-B radiation in <i>Ulva</i> canopies from southern Spain

“…Additionally, mats were exposed to unfiltered solar radiation and also placed under UG-5 filters (Schott, Mainz, Germany), which almost completely absorb PAR but exhibit a high transmission below 400 nm, allowing both UV-A and UV-B to pass. Canopies exposed to unfiltered solar radiation were equipped with biological UVdosimeters (Viospor, Biosense, Germany; see Quintern et al (1992) and Furusawa et al (1998) for reference) under Ulva layer one, two and three (see Fig. 1).…”

Resistance ofBacillusEndospores to Extreme Terrestrial and Extraterrestrial Environments

“…Further attempts to extend this spore dosimetry include the comparisons of dose-rate profiles at several sites in the northern hemisphere (120) and continuous monthly biomonitoring at several sites, including the tropics (121). More recently, a dosimetric system based on measuring protein synthesis during germination of UV-irradiated B. subtilis spores immobilized in a biofilm and subsequent growth has been developed (158) and was used to measure the biologically harmful effects of the increase in UV flux accompanying the seasonal appearance of the "ozone hole" over Antarctica. This study demonstrated that spore dosimetry can indeed detect changes in the depth of the ozone layer, but again a simple response of the dosimeter to changes in ozone column thickness was insufficient to explain all of the phenomena observed (159).…”

“…Biologically effective irradiances as a function of the simulated ozone column thickness were measured with B. subtilis spores immobilized in a biofilm (158) and compared to expected irradiances, using radiative transfer calculations and the biofilm action spectrum. After the mission, the biofilms were incubated and stained, and optical densities indicative of the biological activity were determined for each exposure condition by image analysis.…”

Space Microbiology

“…To gain a quantitative assessment of the implications of progressive ozone depletion for life on Earth, extraterrestrial solar radiation was used in a space experiment as a natural on May 9, 2018 by guest http://mmbr.asm.org/ UV source to irradiate spores of Bacillus subtilis 168 in a biological dosimeter "biofilm" (109). This biofilm technique directly weights the incident spectral components of the environmental UV radiation according to their biological effectiveness (179,210,211). During the German Spacelab mission D2 (Tables 1 and 3), precalibrated "biofilms" consisting of dry monolayers of immobilized spores of B. subtilis 168 were exposed for defined intervals to extraterrestrial solar radiation that was filtered through an optical filtering system to simulate different ozone column thicknesses down to very low values.…”