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Title: Molecular structure and relationships of Pseudomonas plasmids
Author: Bayley, Susan Ann
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1978
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Plasmid deoxyribonucleic acid was isolated from thirteen Pseudomonas strains judged on genetic criteria to carry plasmids coding for the degradation of toluene and m- and p-xylenes (TOL plasmids). Most strains harboured a single plasmid species, but two strains carried two size classes, and a third strain (MT 14) carried plasmids that fell into a range of size classes. Five of the thirteen strains harboured plasmids that were indistinguishable on the basis of size and electrophoresis pattern of endonuclease-generated fragments. Two other strains carried plasmids that were indistinguishable from each other but different from those of the first group. The remaining strains carried unique plasmids. Some plasmids could be transformed into a P. putida strain to give Tol+ progeny. A set of independently-arising Tol derivatives of strain P. putida (arvilla) mt-2 were studied. Some had lost the unique plasmid carried by the parent strain. In others this plasmid had suffered a deletion of a specific region of about 27 MA. Plasmid DNA from m-toluate grown cells of strain MT 14 ranged in size from 25 to 202 M_d. However, after serial subculture of such cells on L-broth, plasmid DNA from a Tol+ clone fell into a single size class of 4+8 Md. After serial subculture of this clone on m-toluate the original distribution was again observed. Endonuclease digestion patterns suggest that the larger plasmid species may be multimers of the 48 Md species. The relationships between plasmids of the same, and of different, incompatibility groups were examined by hybridisation of radioactively labelled plasmid DNA probes to nitrocellulose bound fragmentation patterns of endonuclease digests of plasmid DNA. Plasmids of the same group showed a considerable amount of homology even when the group contained both drug resistance plasmids and degradative plasmids. However, plasmids of different groups had few common sequences.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available