Characterization of bacteriophage CP1, an organic solvent sensitive phage associated with Pseudomonas cepacia

Abstract

Pseudomonas cepacia strain 249 has been found to harbor an organic solvent sensitive phage, CP1, which is active on other P. cepacia strains. The efficiency of plating of CP1 was dependent upon the strain on which it was propagated and the strain used as indicator, implying the operation of host restriction and modification systems in certain of the strains. Strain 383 which was used routinely for propagation of CP1 appears to lack such systems. To obtain high-titer lysates it was important to add EDTA to the infected cultures at the onset of lysis to block attachment of phage particles to cell debris. CP1 possesses a distinct head (55 nm in diameter) and a broad contractile tail (15 x 145 nm). Fluorescent staining of phage preparations with acridine orange indicated that CP1 contains double-stranded DNA. CP1 particles contained about 5 X 10(-17) g each of protein and DNA for a total particle weight of 10(-16) g. The apparent molecular weight of CP1 DNA estimated from its sedimentation behavior and the particle content of DNA was about 3 X 10(7). Thermal-denaturation studies indicated that the G + C content of CP1 DNA (65%) was lower than that of DNA of its P. cepacia host (71% G + C). The mechanism of inactivation of CP1 by chloroform appears to be related to tail contraction caused by this agent. An atypical reverse contraction of the tail sheath was noted in about 45% of the inactivated particles. No phospholipid was detected in purified preparations of CP1 (less than 4 X 10(19) g/PFU). The results suggest that inactivation of CP1 by organic solvents involves alteration of a component (presumably a protein) of the phage tail.