Abstract

Metabolic alterations in bacterial hosts caused by virus infections have been studied for the last thirty years. The virulent T-even bacteriophages have been studied the most and have been shown to be responsible for the induction of a number of new, virus-specific enzymes that are necessary for successful phage growth. In addition, the activity of other host enzymes present prior to infection has been found to be increased by T-even infection. Temperate bacteriophages, being more difficult to work with than the virulent viruses, have not been studied as extensively. This is especially true for metabolic studies, since most temperate phage infections lead to lysogeny. Recently though, it has been found that the temperate phage lambda is capable of inducing a virus-specific enzyme in its host.

The bacteriophage P3 normally grows in Salmonella potsdam. It is also capable of infecting Escherichia coli K12, but undergoes a host-controlled modification of its nucleic acid in the E. coli. The resultant P3 is found to be restricted in its growth in the Salmonella host as a result of this restriction.

The deoxythymidine kinase and deoxythymidylate kinase enzyme systems in Salmonella potsdam and Escherichia coli K12, uninfected and infected with bacteriophage P3, were examined. Efforts were made to detect differences in the host enzyme systems themselves and after infection by the bacteriophage.

It was found that virus infection produces a drastic change in the DNA production of the hosts. Infection by P3 produced an initial decrease in DNA synthesis, that was followed by an increase which was greater than DNA synthesis in uninfected bacteria. The increase was greatest in the Salmonella host, but was still evident in the E. coli. Inhibition of phage protein synthesis failed to interfere with this alteration in DNA synthesis in either host. P3, therefore, is able to utilize host enzymes present prior to infection for its nucleic acid production.

When the deoxythymidine kinase systems were studied, it was found that P3 infection has a different effect in the two hosts. E. coli K12 evidently had sufficient amounts of the enzyme present to supply the needs of P3 DNA production. Infection in Salmonella produced an increase of the deoxythymidine kinase of approximately 30 percent. This increase could be prevented if phage-directed protein synthesis was inhibited. There were no noticeable differences between the enzymes in uninfected and phage-infected bacteria when such features as substrate saturation levels, pH optima, metal ion requirements, and optimum enzyme reaction temperatures were examined. Differences were found to exist between the two host enzymes alone with regard to these same properties.

The deoxythymidylate kinase enzyme systems from the two hosts were examined in the same manner as described for deoxythymidine kinase. The results were similar. Differences in enzyme characteristics were found between the host enzymes, but no alteration in characteristics were brought about as a result of phage infection of either host. In a similar manner, P3-infection of Salmonella caused approximately a 50 percent increase in enzymatic activity. No such increase was detected in the E. coli K12 host. This increase could be blocked by inhibiting phage-specific protein synthesis.

While it was not possible in this study to detect the mechanism responsible for the observed increases in enzyme levels in the Salmonella host after infection with P3, we were able to show that a temperate bacteriophage may have a definite effect upon the metabolic activities of this host.

LLU Discipline

Microbiology

Department

Microbiology

School

Graduate School

First Advisor

Robert L. Nutter

Second Advisor

Raymond E. Ryckman

Third Advisor

Benjamin H. S. Lau

Fourth Advisor

Richard E. Beltz

Fifth Advisor

Robert L. Schultz

Degree Name

Doctor of Philosophy (Medical Science)

Degree Level

Ph.D.

Year Degree Awarded

1974

Date (Title Page)

6-1974

Language

English

Library of Congress/MESH Subject Headings

Bacteriophages Salmonella; Escherichia coli; Thymidine Kinase

Type

Dissertation

Page Count

vii; 122

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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