Abstract
The early theory of the destructive action of ultra-violet rays on bacteria was that hydrogen peroxide was produced in the medium. Oker-Blom 1 proved that the death of the bacteria was not caused by hydrogen peroxide, but by the direct action of the rays on the protoplasm of the organism. Burge and Neill 2 found fluorescent organisms to be more resistant to ultra-violet than colon organisms. They attributed the superior resistance of the members of the fluorescent group to their power of converting the short waves into long ones, and thereby escaping the coagulative action of the short waves on the protoplasm.
The investigation reported in this paper was undertaken to determine whether the pigment produced by organisms of the genus Pseudomonas protects these organisms from radiant energy furnished by a quartz mercury-vapor lamp.
A suitable medium for irradiation was first considered. Both plain broth and lactose broth were found unsuitable because they protected the organism from the effects of the ultra-violet. The synthetic asparagine medium proposed by Georgia and Poe 3 was found to be satisfactory.
In the asparagine medium, 12-, 24-, 36-, and 48-hour cultures of several members of the Pseudomonas group were prepared; 10 cc. of each culture were diluted to 100 cc. with sterile water, and 4 cc. of the diluted culture were exposed to the vertical rays of a Gallois mercury-vapor lamp from one to 40 minutes.
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