It has been shown (Devoret and George, 1967; Monk, 1969) that introduction of an ultraviolet-irradiated plasmid into a host bacterium can result in induction of prophage A in a lysogen, or suppression of cell division in a non-lysogen. In this thesis, the effect on cell division has been further studied. Irradiated P1 bacteriophages were used to infect calls of Escherichia coli X12 carrying the uvrA mutation. such cells are unable to excise pyrimidine dimers from DNA. The dimers induced in the phage genome by ultraviolet irradiation (Setlow, 1964) were measured by paper chromatography (Gunther and Prusoff, 1967). Inhibition of cell division was studied with respect to the effects of nutrients and host cell cycle on expression. Attempts were made to demonstrate replication of the damaged phage particle by differential radioactive labelling and density shift experiments. Autoradiography was used to determine the position of the damaged plasmid in the filament which it induced, and also the position of the cell chromosome strands which were present at the time of infection by the phage. The damaged phage was found to be located in the contra of the filament; this was not found when the phage was undamaged or subjected to phage repressor immediately on infection. The segregation pattern of host chromosomes differed from that found in penicillin-induced filaments. Cell membranes of P1-induced filaments, and control, uninfected, cells were examined by polyacrylamide gel electrophoresis (Laemmli, 1970; Lutkenhaus, 1977). The outer membrane of the filaments showed a changed profile, including a novel protein of molecular weight (Weber and Osborn, 1969) 53,000 daltons. The results are discussed in terms of two models, the SOS hypothesis (Radman, 1974) and the blocked replicon hypothesis (Donachie, 1974). The predictions of the blocked replicon hypothesis are fulfilled.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:657159 |
| Date | January 1977 |
| Creators | MacQueen, Hilary A. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/12531 |
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