Extracellular culture concentrates were prepared from Streptomyces viridosporus T7A, Streptomyces badius 252, and Streptomyces setonii 75Vi2 shake flask cultures. Ten-day-heat-treated (70°C) starch-polyethylene degradable plastic films were incubated with shaking with active or inactive enzyme for 3 weeks (37C). Active enzyme illustrated changes in the films' Fourier transform infrared spectra, mechanical properties, and polyethylene molecular weight distributions.
The effect of R plasmids on spontaneous and radiation (ultraviolet and gamma)induced mutability in Pseudomonas aeruginosa was studied in strains containing the radiation-sensitive markers polA3 or rec-2 and the revertable auxotrophic markers hisO27 and trpBl. In the absence of an R plasmid, the radiation-induced mutability was dependent on the recA+ genotype and independent of the polAt genotype, whereas spontaneous mutability was similar in all genetic backgrounds. R plasmids pPL1, R2, and pMG15 increased the ultraviolet radiation survival and ultraviolet-induced mutability of wild-type and polA host cells but did not alter either effect in a recA mutant. These R plasmids also increased the gamma radiation survival and gamma-induced mutability of wild-type host cells but did not alter either effect in a polA or recA mutant. R plasmids pPL1, R2, and pMG15 also enhanced the level of spontaneous mutagenesis in wild-type host cells but not in a polA or recA mutant. These data suggested that a common plasmid gene product(s) may participate in various recA-dependent, error-prone deoxyribonucleic acid repair pathways of P. aeruginosa. The properties of a mutant R plasmid, pPL2, originally selected because it lacked enhanced ultraviolet-induced mutability, supported this conclusion.
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