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Thesis (M.S.)—University of Nebraska—Lincoln, 1966. Department of Microbiology.


Copyright 1966, the author. Used by permission.


Detailed investigations of lethal agents produced by several strains of Bacillus stearothermophilus originated with a survey by Thompson and Shively in 1963 (unpublished). All of the available thermophilic strains were examined for production of agents which demonstrated lethality toward other members of the same species. Many of the lethal agents proved to be bacteriophage, but in a few instances a non-sedimentable agent was found. One strain, NU-2, produced an agent which was highly active against most of the other strains and was also non-sedimentable.

With this discovery an active program was initiated to investigate the properties of the antibacterial agent produced by NU-2. It was suspected that the agent was bacteriocin-like, for several similarities existed between bacteriocins and the agent from NU-2. Bacteriocins are protein-like substances the biosynthesis of which is associated with a lethal consequence for the producing organisms (Jacob, et al., 1953). The action of a bacteriocin is restricted to only a limited number of related species and some act only on certain strains of the same species which produce them. The agent produced by NU-2 appeared to also possess activity which was strain specific and was produced by a species of Bacillus, a genus which is known to produce bacteriocin. These similarities formed a basis for further study to isolate and characterize the agent from NU-2.

Advisors: Thomas L. Thompson and Jessup M. Shively