Multiplication of Phage λ in Bacteria Unable to Repair Ultraviolet Lesions

Multiplication of phage Λ and/or induced prophage λ was studied in u. v. -irradiated Escherichia coli strains unable to repair u.v. damage. Experiments were carried out to determine the various parameters which control the ''capacity'' of the bacterial cell to support phage λ and/or prophage λ growth. Experimental results demonstrate that, in tire case of phage λ infection, u. v. Irradiation of the host cell has very little effect on the processes of transcription and translation of phage DNA. Our data provide further evidence indicating that after u.v. irradiation de novo synthesis of ribosomes is not required for phage λ growth. Furthermore, all kinds of RNA appear to be very u. v. resistant as compared with host cell DNA. In wild-type strains, the effect of cell exposure to u. v. light on phage λ multiplication is mainly a consequence of indirect damage to the phage genome due to cellular repair processes. In host cells unable to repair u.v. lesions produced in the bacterial DNA, phage λ multiplication is comparatively facilitated. On the other hand, development of prophage λ after u.v. irradiation is not only dependent upon direct u.v. inactivation but is also influenced by host cell repair and mutation processes. Repair of induced prophage λ appears to account mainly for the shape of the induction curve observed in a lysogenic wild type strain. In a repair-deficient strain lysogenic for a non-inducible prophage, u.v. mutations affecting phage λ property to insert in the bacterial chromosome have been detected. Our results point to the fact that In u. v. irradiated cells the extent of phage or prophage λ multiplication is much more affected by indirect damage to the phage genome resulting from repair processes than by inactivation of the host cell synthetic machinery. (author)