Thesis (Ph. D.)--University of Wisconsin, 1964. / Typescript. Vita. Bibliography: leaves 67-69.

The restriction endonuclease Hpa I cleaves wild type T7 DNA into nineteen fragments. These Hpa I fragments were inserted into the ampicillin resistance gene of the plasmid pBR322. The poly A - poly T method of construction was chosen in order to insure single T7 DNA inserts. Two hundred fifty clones were identified as carrying T7 DNA segments by colony hybridization with ³²P T7⁺ DNA. From these, clones carrying specific areas of the T7 genome were identified by various methods described in this thesis. Clones carrying Hpa I fragments E and G were identified by hybridization with Southern filters of electrophoressed Hpa I digested T7 DNA. Clones carrying most of gene 5 and parts of gene 4 were identified by hybridization with a purified restriction fragment carrying those genes (Hpa I fragment D). Clones containing parts of genes 10 and 11 were identified by marker rescue tests. Marker rescue "spot tests" were developed as a fast screening procedure for T7 genes and rely on generalized recombination between the T7 segment carried by the plasmid and the infecting phage DNA. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate

ABSTRACT Bacteriophages have sparked interest as novel ways to control foodborne pathogens. The application of Salmonella-specific phages as antimicrobial agents was tested against relevant Salmonella isolates of poultry origin. Two different Salmonella-specific phages, A and C, were isolated from enriched sewage. They displayed differences in their host-range but exhibited virulent behaviour towards Salmonella enterica serovar Typhimurium ATCC 13311. Toxicity studies were conducted with individual and combined applications of phages A and C, at an MOI of 1, on Salmonella ATCC 13311. Following 3 hour exposure, both applications were equally effective at reducing Salmonella by approximately 1 x 105 CFU/ml. Similar toxicity profiles were observed with both applications, however, a delay occurred with phage A. We propose that phages A and C have similar infective specificities and that during combination competition for the receptor is overcome by phage C. Neither application eliminated Salmonella to undetectable levels. The presence of phage-resistant mutants is a fundamental issue that will hamper the use of phages as alternate antimicrobial agents.

No description available.

Thesis (Ph. D.)--University of Missouri--Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 161-166). Also available on the Internet.

Photocopy of typescript. / Digitized by Kansas Correctional Industries

Call number: LD2668 .T4 1961 L55

LD2668 .T4 1962 R43

A spontaneous deletion mutant of Bacillus phage φ29 (φ29Δ1) is characterized in the first part of this study. This mutant has a 1,112 base pair deletion, which covers the entire coding sequence of genes 14 and 15 including the early promoter, B2. While lysis is very delayed, the phage DNA synthesis and internal phage development appears to be normal in the cells infected with this deletion mutant. These results indicate that the early functions are intact in φ29Δ1. Results also suggest that genes 14 and 15 are dispensable for bacteriophage φ29 growth, and that the B2 promoter may also be despensable for the early functions of φ29. To further explore the function of gene 15, a DNA fragment of φ29 chromosome, encoding the entire sequence of this gene, has been cloned into the Escherichia coli expression vector pPLc245, under the control of the phage lambda major early leftward promoter, PL. Upon heat induction, a protein with an apparent size of 26 kdal was over-produced. This protein has been purified to near homogeneity and confirmed to be the product of gene 15 by amino acid sequence analysis of its N terminus. The purified product of gene 15 has a lysozyme activity similar to the other phage-type lysozymes: products of phage T4 gene e and of phage P22 gene 19. This is the first lysozyme to be cloned and purified from a gram positive system. Bacteriophage φ29 lysozyme has been characterized in the last part of this study. Results show that this enzyme seems to more active than hen egg-white lysozyme against B. subtilis, E. coli, and M. lysodeikticus cells. Most of the characteristics of φ29 lysozyme appears to be similar to the P22 and T4 lysozymes, however, φ29 lysozyme seems to be about 2 times more thermostable than the other two lysozymes.

In batch experiments at pH's 5 and 7, the partitioning of MS-2 between water and silica (unbonded) was compared with the partitioning between water and silica with 6.5 percent of the surface covered by hydrophobic C18 chains (bonded). The roles of double-layer and van der Waals forces in partitioning were explored by modeling the potential energies of interaction. MS-2 adsorption to unbonded silica was negligible at pH 7, but did occur at pH 5. Adsorption was independent of pH with the bonded silica and approximately 2.6 orders of magnitude greater than the unbonded at pH 5, suggesting the importance of hydrophobic partitioning. The total potential energies of interaction, which closely approach the pH-independent van der Waals potentials, are similar in magnitude for all pH's or silica types, and have no positive (repulsive) values. The insignificant contribution of the double-layer potentials suggests that these pH-dependent forces may not account for the pH-dependent adsorption observed with the unbonded silica.