Abstract

Five new bacteriophages were isolated from lysogenic S. potsdam in this laboratory. Group B phages (P3 and P9a) were found to have unique properties, including their capability to infect strains of E. coli K-12 and E. coli C+/L. Passage of the phages through these hosts modified them (host-controlled modification) so that their ability to infect their original host, S. potsdam, was reduced and only 1-4 per million were able to form plaques.

To help elucidate the biochemical basis of host-controlled modification in the Salmonella potsdam group of bacteriophages, the clear plaque mutant of one of them, P3-c1 •S, was selected for study. Three strains of E. coli K-12, in which the phage grew and were modified, were tested as sensitive hosts. Since the phage yield was higher in strain MSC64 (designated in our department as E. coli K-5) , it was utilized throughout the project. The phage, passed through this host, was identified as P3-c1•S•K5.

The phage, P3-c1•S•K5, was found to be stable without EDTA, unlike P3-c1•S. For optimum growth in E. coli K5 in L-broth, it was necessary to add 6.25 x 10-3M calcium ion. After four passages in E. coli K5, the efficiency of plating of the phage was 4.2 x 10-6 on S. potsdam when plating on E. coli was used as a standard. Finally, P3-c1•S•K5 plated with equal efficiency on Shigella felxneri and the resulting phage, P3-c1•S•K5 SF was completely restricted by SP2-R indicating a broad host range for the E. coli-grown Salmonella phage and the probability that strain specific antigens were not required receptor sites as in group A Salmonella phages.

Indications of the general similarity of the basic phage structures was based on the susceptibility of both the E. coli-grown and Salmonella-grown P3 to 30% cesium chloride and their resistance to inactivation by 50% potassium tartrate.

A thin layer chromatography method was used to separate the mononucleotides from phenol-extracted P3-c1•S•K5 DNA after digestion with DNase and venom phosphodiesterase. Although the technique worked well for calf-thymus DNA and base-ratio results compared favorably with those in the literature, dGMP and dCMP from the phage DNA did not have equimolar values. This may have been due to adsorbed guanine-containing materials since the phage DNA was not precipitated and washed prior to digestion.

Experiments with adenine-2-H3, to determine the mole percent of MAP in the respective phage DNA's, revealed that the restricted P3-c1•S•K5 phage DNA contained an average of 0.66% MAP and the unrestricted P3-C1•S•DNA contained an average of 1.15% MAP, the difference of which would represent approximately 95 methyl groups per phage DNA molecule. Restriction, however, is probably due not merely to a non-specific decrease in the MAP level on the phage DNA, after passage through E. coli, but rather to the lack of methylation of particular specific adenines in the E. coli-passed phage DNA molecules.

LLU Discipline

Microbiology

Department

Microbiology

School

Graduate School

First Advisor

Robert L. Nutter

Second Advisor

Leonard R. Bullas

Third Advisor

R. Bruce Wilcox

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

1971

Date (Title Page)

5-1971

Language

English

Library of Congress/MESH Subject Headings

Salmonella Phages; Escherichia coli

Type

Thesis

Page Count

vii; 48

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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