P1 bacteriophage and Tol system mutants

by Smerk, Cari L.

Dr. Ray A. Larsen, Advisor The integrity of the outer membrane of Gram negative bacteria is dependent upon proteins of the Tol system, which transduce cytoplasmic-membrane derived energy to as yet unidentified outer membrane targets (Vianney et al., 1996). Mutations affecting the Tol system of Escherichia coli render the cells resistant to a bacteriophage called P1 by blocking the phage maturation process in some way. This does not involve outer membrane interactions, as a mutant in the energy transucer (TolA) retained wild type levels of phage sensitivity. Conversely, mutations affecting the energy harvesting complex component, TolQ, were resistant to lysis by bacteriophage P1. Further characterization of specific Tol system mutants suggested that phage maturation was not coupled to energy transduction, nor to infection of the cells by the phage. Quantification of the number of phage produced by strains lacking this protein also suggests that the maturation of P1 phage requires conditions influenced by TolQ. This study aims to identify the role that the TolQ protein plays in the phage maturation process. Strains of cells were inoculated with bacteriophage P1 and the resulting production by the phage of viable progeny were determined using one step growth curves (Ellis and Delbruck, 1938). Strains that were lacking the TolQ protein rendered P1 unable to produce the characteristic burst of progeny phage after a single generation of phage. E. coli strains containing the paralogous ExbB were also unable to produce viable phage progeny in the absence of TolQ, suggesting that this role in phage maturation is unique to the TolQ protein. This role is also independent of the energy harvesting function of TolQ, as a strain containing an energetically inactive TolQ protein with a iii point mutation are able to produce enough viable progeny in one generation of phage to constitute a burst. This data suggests that there is some unique, undetermined function of TolQ that is parasitized by the P1 bacteriophage in order to mature and produce viable, infectious progeny. iv