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The objective of this study was to measure rigorously the ultraviolet (UV) inactivationspectrum of Bacillus subtilis spores between 220 to 300 nm and to compare it topreviously published B. subtilis spore spectra and the standard DNA absorbance spectrum.Spore suspensions were exposed to quasi-parallel UV light generated from a mediumpressure mercury lamp. Ten selected wavelength ranges were isolated using a set ofnarrow band-pass filters. A low pressure mercury arc lamp was also employed togenerate germicidal monochromatic radiation at 254 nm. A non-linear multiple-targetmodel was used to fit the UV fluence - inactivation response curve that was generated foreach wavelength band, and the inactivation rate constant (k) and the number of criticaltargets (nc) were estimated using a non-linear regression fit. The action spectrumobtained for the B. subtilis spores in this study was found to be significantly differentfrom action spectra reported previously for the same spore strain, particularly at lowerwavelengths ( 240 nm). Proposed explanations for the difference include differences inmethods for generating monochromatic UV light and measuring UV irradiancemeasurements; however, the difference may also lie with the methods used to model thefluence-inactivation response. The B. subtilis spore action spectrum determined in thisstudy was also significantly different from the standard absorbance spectrum of DNAisolated from other organisms, especially at lower wavelengths. This finding suggeststhat use of absorbance spectrum data of DNA isolated from other species may result ininaccurate estimation of the germicidal fluence (UV dose) produced from mediumpressure UV lamps for surrogate microorganism or target pathogens. Includes 22 references, table, figures.

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Edition: Vol. - No. Published: 11/01/2006 Number of Pages: 10File Size: 1 file , 400 KB