Interplay between the Temperate Phages PY54 and N15, Linear Plasmid Prophages with Covalently Closed Ends

Abstract

The objective of this study was to determine whether the temperate Yersinia enterocolitica phage PY54 may interact with the related Escherichia coli phage N15 during both the lysogenic and the lytic cycle in the same cell. The PY54 and N15 prophages are linear plasmids which have been shown to be compatible and stably replicating in E. coli and Yersinia. In E. coli, the PY54 prophage does not restrict N15 propagation. In contrast, N15 reduces by use of its cor gene the susceptibility of Yersinia strains to PY54. Doubly lysogenic E. coli strains release PY54 virions, some of which apparently contain the N15 genome. Further experiments with replicative miniplasmid derivatives of PY54, N15, and the related Klebsiella oxytoca phage KO2 demonstrated that the KO2 and N15 plasmid prophages belong to the same incompatibility group.Escherichia coli phage N15 (16), PY54 isolated from Yersinia enterocolitica (10), and the Klebsiella oxytoca phage KO2 (5) are the only known temperate phages whose prophages are linear plasmids with terminal hairpins (telomeres). Virions of the three phages contain a linear genome with cohesive ends. Each phage and its respective plasmid prophage are circularly permuted molecules with sizes of 46.3 kb (N15 and PY54) or 51.6 kb (KO2). Sequence analyses revealed similar genome organizations of the three phages (5). The left arm of the genomes carries mainly genes for virion assembly and plasmid partitioning (sop and spy). The right arm contains the protelomerase gene (tel) essential for the generation of the telomeres, a large gene encoding a multifunctional replication protein (RepA), immunity and anti-immunity genes (e.g., cB, cro, and antA), and genes contributing to host cell lysis. Overall the left arm of PY54 is more closely related to KO2 than to N15, whereas N15 and KO2 show the strongest similarities in the right arm. As the genomes of all three phages are mosaically related to and due to homologies to lambda-like phages, it has been suggested to include the telomere phages as a subgroup of the lambdoid phage family (5). Members of this family can interact with each other or with unrelated phages. Phage P22, for example, encodes an antirepressor (Ant) which is capable of inducing resident lambdoid phages by neutralizing the repressor already present in the cell (3). On the other hand, lambda rex genes prevent the growth of rII mutants of phage T4 (2), whereas the HK022 transcription termination factor Nun prematurely terminates early transcripts (13). Besides these interactions, some lambdoid phages can easily recombine with each other, producing functional hybrids (7). Campbell and Botstein (4) defined lambdoid phages as being capable of productive genetic recombination with . Horizontal gene exchange is therefore suggested to be a major component of evolution for these viruses (8).In this work, we studied possible interactions between the telomere phages during their life cycles. The experiments were carried out to answer the question whether the detected DNA similarities between the...

The diverse genetic switch of enterobacterial and marine telomere phages

“…The plasmid prophages of N15 and fKO2 belong to the same incompatibility group while the PY54 prophage belongs to a separate group and thus is compatible with the 2 other plasmids. 6 Telomere phages have also been found in marine bacteria. While the phages VP58.5, VP882 and vB_VpaM_MAR were isolated from V. parahaemolyticus strains, [7][8][9] phage fHAP-1 was recovered from Halomonas aquamarina.…”

“…1 However, experimental data on this issue are still missing even though the function of the N15 and PY54 prophage repressors has already been demonstrated. 3,6 Lytic repressor activity of the telomere phages has been demonstrated only for Cro of PY54. 3 This protein revealed a high binding specificity for a single operator site (O R 3) on the PY54 genome and did not bind to closely related N15 and fKO2 operator sites.…”

The Linear Plasmid Prophage Vp58.5 of Vibrio parahaemolyticus Is Closely Related to the Integrating Phage VHML and Constitutes a New Incompatibility Group of Telomere Phages

“…Transformation experiments revealed that the plasmid is able to replicate in V. parahaemolyticus and also in E. coli and Y. enterocolitica. To study the compatibility between pJH1201 and other telomere phage replicons, E. coli and Yersinia transformants harboring pJH1201 were lysogenized with the phage mutants N15-C02 (Cm r ) and PY54-A (Km r ), respectively, described in a previous study (19). Doubly resistant lysogens which appeared on selective agar were analyzed with respect to their plasmid content.…”

“…repA of N15 and PY54 was shown to harbor the prophage replication origin and to function as a circular minimal replicon (35,42). Compatibility studies demonstrated that the N15 and ⌽KO2 plasmids belong to the same incompatibility group, whereas the PY54 plasmid is able to coexist with these two prophages in doubly lysogenic E. coli and Y. enterocolitica hosts (19).…”

“…The Vp58.5 miniplasmid pJH1201 (Tc r ) was introduced into E. coli C-1a and Y. enterocolitica 83/88/2. Thereafter, transformants were lysogenized with the N15 mutant C02 (Cm r ) and PY54 mutant A (Km r ), respectively (19). Selection of lysogens containing the respective prophage and the miniplasmid pJH1201 was achieved by plating infected bacteria on agar containing tetracycline and kanamycin (pJH1201 and PY54-A) or tetracycline and chloramphenicol (pJH1201 and N15-C02).…”