Regulation of methanol oxidation and carbon dioxide fixation in Xanthobacter strain 25a grown in continuous culture
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The regulation of C1-metabolism in Xanthobacter strain 25a was studied during growth of the organism on acetate, formate and methanol in chemostat cultures. No activity of methanol dehydrogenase (MDH), formate dehydrogenase (FDS) or ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisC/O) could be detected in cells grown on acetate alone over a range of dilution rates tested. Addition of methanol or formate to the feed resulted in the immediate induction of MDH and FDH and complete utilization (D=0.10 h-1) of acetate and the C1-substrates. The activities of these enzymes rapidly dropped at the higher growth rates, which suggests that their synthesis is further controlled via repression by “heterotrophic” substrates such as acetate. Synthesis of RuBisC/O already occurred at low methanol concentrations in the feed, resulting in additive growth yields on acetate/methanol mixtures. The energy generated in the oxidation of formate initially allowed an increased assimilation of acetate (and a decreased dissimilation), resulting in enhanced growth yields on the mixture. RuBisC/O activity could only be detected at the higher formate/acetate ratios in the feed. The data suggest that synthesis of RuBisC/O and CO2 fixation via the Calvin cycle in Xanthobacter strain 25 a is controlled via a (de)repression mechanism, as is the case in other facultatively autotrophic bacteria. Autotrophic CO2 fixation only occurs under conditions with a diminished supply of “heterotrophic” carbon sources and a sufficiently high availability of suitable energy sources. The latter point is further supported by the clearly more pronounced derepressing effect exerted by methanol compared to formate.
Key wordsXanthobacter Methanol Formate Methylotrophy Autotrophy Calvin cycle Regulation Continuous culture RuBisC/O Carbon dioxide fixation
pyrrolo quinoline quinone
tricarboxylic acid cycle
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- DijkhuizenL, HarderW (1984) Current views on the regulation of autotrophic carbon dioxide fixation via the Calvin cycle in bacteria. Antonie van Leeuwenhoek; J Microbiol Serol 50:473–487Google Scholar
- GreenwoodJA, JonesCW (1986) Environmental regulation of the methanol oxidase system of Methylophilus methylotrophus. J Gen Microbiol 132:1247–1256Google Scholar
- JanssenDB, KeuningS, WitholtB (1987) Involvement of a quinoprotein alcohol dehydrogenase and an NAD-dependent aldehyde dehydrogenase in 2-chloroethanol metabolism in Xanthobacter autotrophicus GJ10. J Gen Microbiol 133:85–92Google Scholar
- Meijer WG, Arnberg AC, Enequist HG, Terpstra P, Lidstrom ME, Dijkhuizen L (1990b) Identification and organization of carbon dioxide fixation genes in Xanthobacter flavus H4-14. Mol Gen Genet (in press)Google Scholar
- Meijer WG, Enequist HG, Terpstra P, Dijkhuizen L (1990c) Nucleotide sequences of the genes encoding fructosebisphosphatase and phosphoribulokinase from Xanthobacter flavus H4-14. J Gen Microbiol (in press)Google Scholar
- WiegelJKW, SchlegelHG (1984) Genus Xanthobacter Wiegel, Wilke, Baumgarten, Opitz and Schlegel 1978, 573AL. In: KriegNR, HoltJG (eds) Bergey's manual of systematic bacteriology, vol 1. Williams and Wilkins, Baltimore London, pp 325–333Google Scholar
- WilkeD (1980) Conjugational gene transfer in Xanthobacter autotrophicus GZ29. J Gen Microbiol 117:431–436Google Scholar