Vary, Patricia S.
M.S. (Master of Science)
Department of Biological Sciences
Bacillus megaterium; Bacteria; Mutation (Biology)
Mutants of Bacillus megaterium QMB1551 sensitive to mitomycin C or MMS were isolated and characterized phenotypically. Cellular survival to UV light and gamma rays was determined, as well as transductional recombination. Of the mutants tested, three were found to be sensitive to UV irradiation, but remained recombination proficient. These strains, which were more sensitive from 2 to 5 percent of the parent strain, were designated as uvr mutants. Three strains were found to have transduction frequencies less than 1.35 percent to less than 0.32 percent of the parental strains, even though they supported plaque formation with MP13. These mutants seem to have a defect in recombination and were designated recombination-deficient (recˉ) mutants. Efficiency of plating and cell viabilities of the rec mutants showed little reduction in either of these properties, thereby eliminating the possibility for these being the cause of the recombination deficiencies. Sensitivities of the rec and uvr strains to UV and gamma radiation were compared to the recE4, recAl, uvrA19 and uvrB109 strains of Bacillus subtilis. In each case, the strains of B. megaterium, including the parental strains, showed a higher percentage of cell survival than B. subtilis. This may be a reflection of the larger amount of DNA present in B. megaterium. The abilities of the rec and uvr strains for host cell reactivation of UV-damaged phage DNA, were also determined. The results show that the rec mutants were proficient in reactivating MP13 at wild-type levels, while the abilities of the three uvr mutants were reduced from 35 to 54 percent of wild type. Revertants of the rec strains were isolated to determine if the pleiotrophic effects of MitC, MMS and UV and gamma ray sensitivity and recombination deficiency were the result of a single mutation in a recombination locus. Partial reversion of all the effects were observed. Preliminary attempts to map the rec mutants revealed no linkages in crosses with pyrB, cysC and pheA. The rec mutants specifically should prove useful in current investigation in this laboratory of recombinant plasmid stability in B. megaterium.
English, Jami D., "Isolation of recombination-deficient and ultraviolet-sensitive mutants of Bacillus megaterium QMB1551" (1985). Graduate Research Theses & Dissertations. 3682.
v, 72 pages
Northern Illinois University
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