Ultraviolet Induction Properties of SALMONELLA POTSDAM Bacteriophages
Three lysogenic strains of Salmonella potsdam were studied to determine whether or not they were inducible by ultraviolet light under certain conditions. The strains examined were SP3, SP4, and SP9. SP3 and SP4 contained a single prophage each and SP9 contained two prophages P9a and P9c. The ultraviolet light sensitivities of each of these lysogenic strains and the indicator strain SP2 were also examined. All three lysogenic strains were found to be inducible. SP3 was induced an average of 3.59% and SP4 an average of 2.21%. The difference between the induction percentages of SP3 and SP4 was not statistically significant. Doubly lysogenic SP9 was also inducible with P9a/2 being induced an average of 14.6% and P9c/2 an average of 16.6%. The difference between the average induction percent of P9a/2 and P9c/2 was not statistically significant. The burst size and range for each of the phages for each bacterial strain was examined. The mean burst size of P3/2 was 11.1 (stnd. dev. 17.8), and of SP4 it was 13.4 (stnd. dev. 12.7). The difference between the mean burst sizes of these two strains was not found to be statistically significant. The mean burst sizes of the SP9 phages were 55.2 (stnd. dev. 52,6) for P9a/2 and 42.4 (stnd. dev. 54,5) for P9c/2. Again the difference between the mean burst sizes was found not to be statistically significant. The ultraviolet inactivation experiments showed that SP9 was the most sensitive; SP3 was intermediate; while SP2 and SP4 were the least sensitive and, except for the first 20 seconds of irradiation, equally sensitive. During the first 20 seconds SP4 was less sensitive than SP2. The velocity of inactivation constants averaged 0.20 for SP2, 0.27 for SP3, and 0.22 for SP4 over the main portion of their curves. SP9 showed an ever increasing resistance to the irradiation and its velocity "constant" decreased steadily from 0.73 between zero and 5 seconds to 0.048 between 30 and 40 seconds. Visual observation of the UV-treated cultures showed that the rise in turbidity of the cultures during the first 1.5 hours of incubation was caused by the increase in length of a high proportion of the cells in the culture.
Bacteriology, Biology, Salmonella; Ultraviolet Rays
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