EFFECTS OF X-RAYS PRODUCED AT 50 KILOVOLTS ON DIFFERENT SPECIES OF BACTERIA

Abstract

The effects of soft X-ray irradiation of 6 spp. of bacteria were studied. Cultures were grown on nutrient agar slants for one day at 37[degree] or 30[degree]C. Suspensions of each culture in different concns. were made, and 1 ml. samples were irradiated with dosages ranging from 572 to 25,320 r. The rate of destruction corresponded to a lst-order reaction. The percentage of bacteria of a given species killed by a specific dosage of X-rays was the same, irrespective of the initial concn. of the bacteria in the suspension. This indicates that the bacteria were destroyed by soft X-rays according to the "direct hit" theory of radiation. Calculation of the total dosages that resulted in 37% survival of the organisms studied showed that Staphylococcus aureus was the most radio-resistant of the spp. of bacteria studied. The other spp. in the order of decreasing resistance, were Escherichia coli, Aerobacter aerogenes, Serratia marcescens, Pseudomonas aeruginosa, and P. fluorescens.