Abstract
Summary
The results secured in these investigations show that the initial number of cells influences survival of microörganisms exposed to ultraviolet light. Dilute suspensions are destroyed more quickly than heavy ones. The order of decreasing resistance for the species used was: Staphylococcus aureus, Escherichia coli (Frank strain), Escherichia coli (American Type Collection No. 4348), and Serratia marcescens. For the mold-spores studied the order of decreasing resistance was: Aspergillus glaucus, Aspergillus niger, Penicillium, and Mucor.
Cardboard strips, which had been inoculated by immersion in a suspension of mold-spores, were not as thoroughly sterilized as were the suspensions themselves, when exposed to ultraviolet light in Petri dishes. On many of the strips it was possible to determine that the colonies originated from the under side of the strip more frequently than from the upper side. This was interpreted as indicating that indirect irradiation is much less effective than direct irradiation.
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