A series of oligomycin resistant mutants has been isolated following u.v. irradiation. The phenotypic and genotypic properties of these mutants, which show high levels of resistance to oligomycin and rutamycin, have been investigated and, on the basis of these results, it has been possible to divide the mutants into two main classes, class I and class II. Class I Mutants of this class show low levels of cross resistance (increases of two-to-four-fold) to various uncouplers such as TTFB, 1799 and chloro CCP, to inhibitors of oxidative phosphorylation like aurovertin and triethyltin, to the inhibitor of electron transport, antimycin A, and protein synthesis inhibitors such as cycloheximide, mikamycin, chloramphenicol and erythromycin. The mutants are apparently, however, resistant to neither DNP nor octylDNP. In a high percentage of the mutants, exposure to low temperatures (20ºC) resulted in the loss of the primary resistance to oligomycin and rutamycin, though the secondary cross resistances were apparently unaffected. No effect of either high or low temperatures on either the fermentable or non-fermentable growth of these mutants were apparent. No alteration in the growth rate of the majority of the strains or in their appearance on electron microscopic examination was detected, though their growth yield is 15 – 20% lower than the wild type strain. Genetic analysis has revealed that this class of mutant clearly differs genotypically as well as phenotypically from the class II mutants and moreover, had indicated that the determinant controlling oligomycin resistance is a nuclear gene. The genetics of the mutants exhibited many anomalous features, which remain to be explained, many of the experiments in this thesis describing, rather than explaining the phenomena observed. Class II The mutants in this class show resistance only to oligomycin and rutamycin. No cold or heat sensitivity of growth was observed and only one mutant in this class shoed any temperature sensitivity with regard to its oligomycin resistance. No alteration in the growth rate, growth yield or mitochondrial morphology of any of the mutants in this class was found. Genetic analysis of these mutants revealed that all the mutants tested showed cytoplasmic inheritance, the genetic determinant being located on the mitochondrial DNA. Allelism tests have demonstrated that genotypically the class is not homogeneous and the mutants were sub-divided into two non-allelic recombination groups. The genetic determinants concerned in each sub-group were confirmed to lie on mDNA.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:594980 |
| Date | January 1972 |
| Creators | Avner, Philip R. |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/73642/ |
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