The Effect of X-Ray Upon Bacteriophage and Upon the Bacterial Organism

Abstract

A number of workers recently have demonstrated that it is possible to produce variants among both plants and animals by exposure to the effect of X-rays We, in turn, have endeavored to demonstrate change by a similar procedure applied to the Bacteriophage and to the organism susceptible to the Bacteriophage, following suggestions made by Dr. Olson.

Seven strains of B. coli bacteriophage were selected and for each of these we cultured the particular strain of B. coli acted upon by its respective strain of bacteriophage. There were selected 7 coli bacteriophages and 6 strains of B. coli for this series of experiments. These bacteriophages were effective as follows upon the bacterial strains: one for all the strains, one for 5, one for 2 and 3 could lyse only one strain each of the organisms. There were thus 42 combinations possible in such a set up of tubes in case any variation were to appear.

The following methods for exposure were followed. The organisms were young cultures in the phase of positive logarithmic growth in beef infusion broth and the phages were recent filtrates in the same medium. These were contained within lead free glass test tubes. Exposure to X-ray was carried out at a distance of approximately fourteen inches from the target of a Roentgen tube actuated by approximately 75,000 volts of electricity. The exposure period was 30 minutes. Following this treatment each baeteriophage was placed in contact with untreated organisms of each culture and the exposed bacterial culture was set up with each of the unexposed bacteriophages. For control purposes a similar series of unexposed bacteriophages and bacterial cultures were used.

The following results were obtained. By this method of treatment 3 of the bacteriophages developed reduced effectiveness when brought into contact with organisms shown previously to be susceptible to them in the control series.