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Gas and Indole Variants of Escherichia Coli at Elevated Incubation Temperature [microform]

出版	Thesis (M.Sc.)--University of Alberta, 1982
ISBN	03151243859780315124387
URL	http://books.google.com.hk/books?id=SiS-0AEACAAJ&hl=&source=gbs_api

註釋The effect of various treatments on the ability of Enterobacteriaceae to produce indole from tryptophan, and acid and gas from lactose was studied. No variants were obtained for these characteristics at 35.0°C, while at 44.5°C variants were obtained for two strains of E. coli. All of the E. coli variants failed to produce gas in EC or lactose broth at 44.5°C, using the conventional Durham tube method, but only 3 variants failed to produce indole from tryptophan at 44.5°C. The E. col / stock cultures from which these variants were obtained normally lost these functions at 47.0 and 48.0°C. The maximum growth temperature for both E. coli stock and variant cultures in TSB, EC, and lactose broths was 48.0°C. Loss of the characteristics by the variants could not be attributed to a change in growth range. No variants were obtained for the E . col I cultures with repeated transfer or prolonged storage of the stock cultures on nutrient agar slants at 4°C, nor as a result of daily sublethal heat treatment at 52°C for 15 min. in Tryptic Soy Broth (TSB). A few variants were found as a result of repeated UV treatment (5 min. daily germicidal UV irradiation in TSB), extended storage at 4, 35, and 45°C in TSB, and cold storage at -16°C. In contrast, variants were found repeatedly when stored on nutrient deficient broth and semisolid agar media at 4°C and -16°C. The variants were shown to be stable upon subculture, suggesting that the treatments generated permanent DNA alterations. E. coli variants which did not produce gas in lactose or EC broth at 44.5°C (Durham tube method) were attributed to a more temperature-sensitive formic hydrogen lyase enzyme. This enzyme produced traces of H 2 and C0 2 gas from lactose at 44.5°C (detected by gas chromatography), about 1/10th to 1/30th of the amount produced at 44.0°C. The generation of temporary E. col i ATCC 11775 variants for gas production in lactose and EC broth at 44.5°C by acridine orange treatment, used to rid the E. col i of non-integrated F plasmids, suggested that the 1ac + genes of these variants may have been associated with their F plasmid and lost during treatment. E. coli variants which failed to produce indole at 44.5°C had a more temperature-sensitive synthesis and activity of tryptophanase. The exact location of the genetic alteration responsible for this variation was not determined.