Spectral radiation involved in protoreactivation of ultraviolet-irradiated cultures of micro-organisms

Abstract

Cultures of E. coli irradiated by ultraviolet energy of λ2537 can be partially reactivated by visible blue light from λ4500 to λ3800. Reactivation becomes most evident in the long-wave ultraviolet in the region of λ3650 or the so-called “black light” band of the mercury spectrum. These results are primarily qualitative. The use of color filters to isolate various bands of tungsten spectra in addition to obtaining monochromatic energy by means of a quartz spectrograph tend to place the region of maximal photoreactivity between λ3500 and λ4500. Simultaneous irradiation of air-borne respiratory micro-organisms with λ2537 ultraviolet and with visible light and near-ultraviolet energy from 4500° K fluorescent tubes showed no significant or measurable reactivation by the latter, even though the illumination was much higher than that generally prevailing indoors.