Frampton, Elon W.
M.S. (Master of Science)
Department of Biological Sciences
Escherichia coli; Bacteriophages
Inducibility of coliphage 15 phage particles, particle distributions, and radiation sensitivities were investigated in four thymine requiring strains derived from Esaherichia ooli strain 15. Strain 15 T“ (requires thymine) was induced after exposure to radiation only while the multiple auxotrophs, strains 555-7 (requires thymine, arginine, methionine, and tryptophan) and TAU-bar (requires thymine, arginine, methionine, tryptophan, proline, and uracil) were induced only when a period of halogenated pyrimidine incorporation preceded exposure to either ultraviolet light or gamma rays. The halogenated analogs tested were 5-bromouracil, 5-bromo- deoxyuridine, 5-fluorouracil, and 5-fluorodeoxyuridine. Cell lysis measurements were used to determine the optimum conditions for induction since coliphage 15 is a non- infectious particle. The optimum conditions for lysis in strains 15 T“, 555-7, and TAU-bar were produced by incorporation of 5-bromodeoxyuridine for forty minutes before exposure to ultraviolet radiation (300 ergs/mm ). Exposure to gamma radiation (20,000 roentgens) also resulted in lysis after 5-bromodeoxyuridine incorporation but not as efficiently. Strain TAU-bar was more refractive to lysis than either 15 T~ or 555-7 and strain JG-151 remained uninducible under any of the conditions. Particles present in lysates were resolved on cesium chloride gradients and also observed by electron microscopy. Strains 555-7 and TAU-bar produced both head and tail particles in their lysates but only tailless heads were recovered on cesium chloride density gradients. Particle distribution in strain 15 T“ was unaffected when 5-bromodeoxyuridine incorporation preceded exposure to ultraviolet radiation (two peaks containing apparently complete phage particles and one peak containing heads without long tails). Free tail particles, however, were observed in lysates of strains 555-7 and TAU-bar suggesting a defective assembly mechanism in these two derivatives. Strain TAU-bar was slightly more resistant than the other inducible strains to inactivation by ultraviolet light and gamma rays. The observation that strain JG-151 was extremely sensitive to inactivation by ultraviolet light suggests that a defective repair system may be related to a failure in prophage excision in this strain.
Dale, Barbara, "Induction of coliphage 15 : influence of halogenated pyrimidines and radiation exposure on derivatives of Escherichia coli strain 15" (1974). Graduate Research Theses & Dissertations. 3556.
vi, 63 pages
Northern Illinois University
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