Some Physical and Chemical Properties of SALMONELLA POTSDAM Bacteriophages

The phages isolated from different lysogenic strains of Salmonella may be divided into different groups on the basis of their heat resistance. In Group A are phages resistant to a temperature of 80°C and in Group B phages that are killed at this temperature. Three temperate bacteriophages P3/2, P4/2 and P9a/2 isolated from lysogenic strains of S. potsdam were investigated. Phage P4/2 is in Group A and phages P3/2 and P9a/2 in Group B. The kinetics of heat inactivation and of ultraviolet light inactivation of each of these phages were compared. Base ratio analysis of the nucleic acid by the method of paper chromatography of each of the bacterial strains and phage P4/2 was also done. Phage P4/2 was examined by electron microscopy. Heat inactivation of phages in buffer solution revealed that P4/2 was most heat resistant, P3/2 was intermediate and P9a/2 was most sensitive. The Arrhenius constant of each phage were determined; for P3/2 it was 73, 280; for P4/2, 84, 630; and for P9a/2, 56, 334. The ultraviolet light inactivation experiments showed that P4/2 was most sensitive; P3/2 was intermediate while P9a/2 was most resistant. The inactivation constants were 0.025 for P3/2; 0.028 for P4/2; 0.020 for P9a/2. Results of a number of tests indicated that phage P4/2 possessed an unusual structure with reference to its nucleic acid. The diphenyalamine test showed that the nucleic acid was DNA; no RNA was detected. The acridine orange test suggested a single stranded configuration of DNA. The molar contents of thymine and adenine were not equivalent, nor were the molar contents of guanine and cytosine. The phage DNA did not resemble in molar ratio of bases either the DNA of the lysogenic culture from which it was isolated, or the culture upon which it was propagated. Thus the evidence strongly suggested that phage P4/2 contains single stranded DNA. The base ratios of the lysogenic and non-lysogenic bacteria were identical. By electron microscopy, P4/2 was revealed as a small phage with a diameter of approximately 59 mμ, probably a dodecahedron and with a short but definite tail about 25 mμ long and 10 mμ wide