This title appears in the Scientific Report :
2010
Studies on central carbon metabolism and respiration of $\textit{Gluconobacter oxydans}$ 621H
Studies on central carbon metabolism and respiration of $\textit{Gluconobacter oxydans}$ 621H
$\textit{Gluconobacter oxydans}$ shows a number of exceptional characteristics, like the biphasic growth on glucose and the incomplete oxidation of glucose to gluconate (phase I, exponential growth,) and ketogluconates (phase II, linear growth), leading to an acidification of the medium down to pH v...
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Personal Name(s): | Hanke, Tanja (Corresponding author) |
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Contributing Institute: |
Biotechnologie 1; IBT-1 |
Imprint: |
Jülich
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
2010
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Physical Description: |
120 S. |
Dissertation Note: |
Universität Düsseldorf, Diss., 2010 |
ISBN: |
978-3-89336-607-1 |
Document Type: |
Book Dissertation / PhD Thesis |
Research Program: |
Biotechnologie |
Series Title: |
Schriften des Forschungszentrums Jülich. Reihe Gesundheit / Health
21 |
Subject (ZB): | |
Publikationsportal JuSER |
$\textit{Gluconobacter oxydans}$ shows a number of exceptional characteristics, like the biphasic growth on glucose and the incomplete oxidation of glucose to gluconate (phase I, exponential growth,) and ketogluconates (phase II, linear growth), leading to an acidification of the medium down to pH values less than 4. Furthermore, growth and metabolism of $\textit{G. oxydans}$ is strongly dependent on the availability of oxygen. In the respiratory chain, two terminal end acceptors are present. The ubiquinol bd oxidase, preferably used under acidic pH, is less efficient in contribution to the proton motive force than the bo$_{3}$ oxidase. An open question was the function of a cytochrome bc$_{1}$ complex as well as soluble cytochrome c$_{552}$, in the absence of a cytochrome c oxidase. For elucidation of the function of these respiratory chain components, a deletion mutant lacking the genes encoding the cytochrome bc$_{1}$ complex was constructed and characterised. When cultivated on mannitol at pH 4 the deletion mutant showed retarded growth and substrate consumption. Therefore, the cytochrome bc$_{1}$ complex is involved in energy supply of the cells under acidic pH when the more inefficient ubiquinol bd oxidase is upregulated. Interestingly, under oxygen limitation the deletion mutant released heme into the culture medium in the late stationary phase. Since hemes $\textit{b}$ and $\textit{c}$ are the prosthetic groups of the cytochrome bc$_{1}$ complex heme excretion of the mutant is a consequence of absence of the corresponding apoenzymes, which is formed under oxygen limitation. The membrane-bound and respiratory chain-linked alcohol dehydrogenase (ADH) was reported to be a component of the respiratory chain and not merely an oxidoreductase. A connection to the cytochrome bc1 complex was investigated in this work. The oxidation velocity of the ADH of the mutant was significantly lower than that of the wild type was. Furthermore, the cytochrome bc$_{1}$ complex was shown to be involved in the energy-dependent activation of the ADH in cells grown at pH 4, but a direct interaction between the cytochrome bc$_{1}$ complex and the ADH was not demonstrated yet. In order to throw light on the regulation of the respiratory chain in conjunction with the overall metabolism, genome-wide DNA microarray analyses were carried out with $\textit{G. oxydans}$ 621H. Three conditions were investigated: I) oxygen limitation vs. oxygen excess, II) cultivation at decreased pH of 4 vs. cultivation at standard pH of 6 and III) growth phase II vs. growth phase I during growth on glucose pH 6, since the cytochrome bc$_{1}$ complex deletion mutant showed growth retardation in growth phase II. Transcriptional analyses of oxygen-limited cells displayed an upregulation of genes [...] |