The morphology and nucleotide composition of DNA of Citrobacter phages.

Citrobacter phages 38/37, 31/37, 40/1 and 8/5, isolated from lysogenic cultures, were concentrated and purified by 2 cycles of differential centrifugation. Electron microscopy of the phages has shown that their particles have similar morphology and that they relate to the morphological group A1. The heads of the phages are hexagonal, 50 +/- 2 nm in diameter. The tail of the phage is straight, 112-152 nm in length, with a contracting sheath 11.5-12.5 nm wide. The tails of the phages 38/37 and 40/1 were found to be slightly longer in comparison with the phages 31/37 and 8/5. Chromatographic investigation of DNA preparations of the phages revealed the presence of 4 nitrous bases. Identification of the latter permitted us to relate them to common nitrous bases. DNA of the phages is double-stranded and belongs to a weakly expressed guanine-cytosine type. The content of guanine and cytosine in DNA of the phage 38/37 amounts to 56.68%, that of the phage 31/37 to 56.75, of the phage 40/1 to 57.36% and of the phage 8/5 to 55.58%. No substantial variations were observed in the DNA composition of the phages.

[Isolation and properties of Citrobacter bacteriophages]. / Vydelenie i svoistva bakteriofagov Citrobacter.

Four phages differing in their antigenic properties, thermosensitivity and spectrum of action have been obtained from Citrobacter lysogenic cultures. To prepare the suspension of Citrobacter phages, phagolysates may be treated with chloroform 1:10 for 30 minutes. The isolated phages have proved to be highly specific. The possibility of distinguishing Citrobacter cultures by means of the phages under study has been shown.