Tales of Seduction and Betrayal: Host Genes Required for Assault of Salmonella by Bacteriophage P22
Lawes, Matthew Charles
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https://hdl.handle.net/2142/86718
Description
Title
Tales of Seduction and Betrayal: Host Genes Required for Assault of Salmonella by Bacteriophage P22
Author(s)
Lawes, Matthew Charles
Issue Date
1997
Doctoral Committee Chair(s)
Maloy, Stanley R.
Department of Study
Microbiology
Discipline
Microbiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Molecular
Language
eng
Abstract
The goal of this thesis was to learn if there are host factors encoded by Salmonella typhimurium that phage P22 requires for completion of its life cycle, especially at the step where phage DNA is translocated across the cytoplasmic membrane into the cell. Bacteria with mutations in any of these host factors required by the phage would gain resistance to infection by P22. Consequently, chemically mutagenized bacteria were exposed to a high multiplicity of a virulent P22 derivative and temperature conditional P22$\rm\sp{r}$ mutants were selected. These P22$\rm\sp{r}$ mutants were sorted into four classes according to which step(s) of the P22 life cycle were affected by the host mutation. (1) Reversible adsorption. Lipopolysaccharide mutants were the predominant class and affected reversible adsorption of the phage, these mutants were not characterized further because they have already been well studied. (2) Irreversible adsorption and ejection. A Ts mutation in the infC (translation initiation factor 3) gene affected the irreversible adsorption of P22, preventing the ejection of DNA into the periplasmic space of the recipient bacterium. The mutant also showed pleiotropic defects in outer membrane integrity and growth at 42$\sp\circ$C. (3) DNA uptake. A Ts mutation, tdx, reduced P22-mediated transduction of the recipient by a factor of 1000-fold. This mutant still adsorbed virus particles normally, suggesting that this gene may encode a host factor directly and specifically involved in the translocation of P22 DNA across the cytoplasmic membrane. (4) Phage maturation. Five independent host mutants were recovered which affected the development or morphogenesis of progeny virus particles, even though the mutants still adsorbed P22 and were transduced by P22 transducing particles. Three of these genes (matA, matB, and matD) mapped to the immediate vicinity of another P22-required maturation gene, opdA, at 80 minutes on the genetic map, but were genetically distinct.
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