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Title: Mandelate dehydrogenases of Acinetobacter calcoaceticus
Author: Hills, Celia A.
ISNI:       0000 0001 3578 638X
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1979
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1. This thesis begins with a description of the main attributes of the genus Acinetobacter, drawing attention to its increasing scientific, economic and medical importance. The microbial metabolism of D- and L-mandelate is then reviewed and present knowledge concerning the control of the pathways summarized. The use of metabolic pathways as a means of deducing evolutionary events in microorganisms is then illustrated by a brief discussion of the ketoadipate pathway and some comparisons are drawn with the pathways of mandelate metabolism. The mechanisms whereby metabolic capabilities might evolve are then exemplified by a number of experimental models of acquisitive evolution in bacteria. The Introduction concludes with a brief description of a number of mutants used in this work which had been isolated from A. calcoaceticus strain NCIB825O (LiDoPi) by previous workers. This wild-type strain can utilize L-mandelate, but is unable to metabolize D-mandelate. Another wild-type strain EBF65/65 (LiDoPi) shows the opposite pattern, utilizing D-mandelate but not L-mandelate. 2. The aims of the experimental work were four-fold: (a) To define the novel pathway by which D-mandelate is utilized in mutants derived from wild-type strain NCIB825O. Preliminary work by Fewson et al. (1976) had suggested that the initial step involved a specific dehydrogenase, giving phenylglyoxylate which is the first intermediate in the pathway for L-mandelate metabolism. It was hoped either to confirm this or to obtain evidence establishing the existence of some other pathway. (b) To examine the novel enzyme involved, which turned out to be a D-mandelate dehydrogenase, and compare it with the original L-mandelate dehydrogenase. (c) To ascertain the mode of regulation of the evolved D-mandelate dehydrogenase in mutants derived from strain NCIB825O and of the regulation of the evolved L-mandelate dehydrogenase and the original D-mandelate dehydrogenase in mutants derived from wild-type strain EBF65/65. (d) To attempt to establish the mutational events underlying the appearance of the pathway by which the two wild-type strains of A. calcoaceticus gained the ability to grow on the second stereoisomer of mandelate. 3. A method was developed to overcome the problem of lysis of some mutant strains. Bacteria were grown for a short time in defined medium using a large nutrient broth inoculum. Cultures were grown at 23°C to obtain high specific activity of D-mandelate dehydrogenase because the enzyme was found to be heat-labile.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available