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Journal of Bacteriology, June 2006, p. 3923-3935, Vol. 188, No. 11
0021-9193/06/$08.00+0     doi:10.1128/JB.01953-05
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Evolution of Immunity and Host Chromosome Integration Site of P2-Like Coliphages

Joakim L. Karlsson, Carlos Cardoso-Palacios, Anders S. Nilsson,* and Elisabeth Haggård-Ljungquist

Department of Genetics, Microbiology and Toxicology, Stockholm University, S-106 91 Stockholm, Sweden

Received 21 December 2005/ Accepted 14 March 2006

The amount and distribution of variation in the genomic region containing the genes in the lytic-lysogenic genetic switch and the sequence that determines the integration site into the host chromosome were analyzed for 38 P2-like phages from Escherichia coli. The genetic switch consists of two convergent mutually exclusive promoters, Pe and Pc, and two repressors, C and Cox. The immunity repressor C blocks the early Pe promoter, leading to the establishment of lysogeny. The Cox repressor blocks expression of Pc, allowing lytic growth. Phylogenetic analyses showed that the C and Cox proteins were distributed into seven distinct classes. The phylogenetic relationship differed between the two proteins, and we showed that homologous recombination plays a major role in creating alterations in the genetic switch, leading to new immunity classes. Analyses of the host integration site for these phages resulted in the discovery of a previously unknown site, and there were at least four regular integration sites. Interestingly, we found no case where phages of the same immunity class had different host attachment sites. The evolution of immunity and integration sites is complex, since it involves interactions both between the phages themselves and between phages and hosts, and often, both regulatory proteins and target DNA must change.

* Corresponding author. Mailing address: Department of Genetics, Microbiology and Toxicology, Stockholm University, S-106 91 Stockholm, Sweden. Phone: 46-8-164549. Fax: 46-8-164315. E-mail: Anders.Nilsson{at}gmt.su.se.

Journal of Bacteriology, June 2006, p. 3923-3935, Vol. 188, No. 11
0021-9193/06/$08.00+0     doi:10.1128/JB.01953-05
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Serra-Moreno, R., Jofre, J., Muniesa, M. (2007). Insertion Site Occupancy by stx2 Bacteriophages Depends on the Locus Availability of the Host Strain Chromosome. J. Bacteriol. 189: 6645-6654 [Abstract] [Full Text]  
  • Ahlgren-Berg, A., Henriksson-Peltola, P., Sehlen, W., Haggard-Ljungquist, E. (2007). A comparison of the DNA binding and bending capacities and the oligomeric states of the immunity repressors of heteroimmune coliphages P2 and W{Phi}. Nucleic Acids Res 35: 3167-3180 [Abstract] [Full Text]  


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