Article

The role of oxygen in the regulation of glucose metabolism, transport and the tricarboxylic acid cycle in Pseudomonas aeruginosa.

Journal of general microbiology 02/1982; 128(1):49-59. DOI: 10.1099/00221287-128-1-49
Source: PubMed

ABSTRACT The effect of dissolved oxygen concentration on the metabolism of glucose in Pseudomonas aeruginosa was studied with chemostat cultures using both single-step and gradual transitions from either ammonium or glucose limitation to oxygen limitation and studying transient and steady states. The pathway of glucose metabolism was regulated by the availability of oxygen. The organism responded to oxygen limitation by adjusting its metabolism of glucose from the extracellular direct oxidative pathway, which produces gluconate and 2-oxogluconate, to the intracellular phosphorylative route. This change was a consequence of decreased activities of glucose dehydrogenase and gluconate dehydrogenase and of the transport systems for gluconate and 2-oxogluconate, and an increased activity of glucose transport, while relatively high activities of hexokinase and glucose-6-phosphate dehydrogenase were maintained. Citrate synthase, isocitrate dehydrogenase and malate dehydrogenase activities responded to changes in dissolved oxygen concentration rather than to changes in the glucose or ammonium concentrations. The effect of oxygen limitation on the oxo-acid dehydrogenases and aconitase was probably due, wholly or in part, to repression by glucose consequent upon the increase in residual glucose concentration. Succinate dehydrogenase was repressed by an increase in ammonium concentration under an oxygen limitation.

0 Bookmarks
 · 
140 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The rhizobacterium Pseudomonas fluorescens CHA0 promotes the growth of various crop plants and protects them against root diseases caused by pathogenic fungi. The main mechanism of disease suppression by this strain is the production of the antifungal compounds 2,4-diacetylphloroglucinol (DAPG) and pyoluteorin (PLT). Direct plant growth promotion can be achieved through solubilization of inorganic phosphates by the production of organic acids, mainly gluconic acid, which is one of the principal acids produced by Pseudomonas spp. The aim of this study was to elucidate the role of gluconic acid production in CHA0. Therefore, mutants were created with deletions in the genes encoding glucose dehydrogenase (gcd) and gluconate dehydrogenase (gad), required for the conversion of glucose to gluconic acid and gluconic acid to 2-ketogluconate, respectively. These enzymes should be of predominant importance for rhizosphere-colonizing biocontrol bacteria, as major carbon sources provided by plant root exudates are made up of glucose. Our results show that the ability of strain CHA0 to acidify its environment and to solubilize mineral phosphate is strongly dependent on its ability to produce gluconic acid. Moreover, we provide evidence that the formation of gluconic acid by CHA0 completely inhibits the production of PLT and partially inhibits that of DAPG. In the Deltagcd mutant, which does not produce gluconic acid, the enhanced production of antifungal compounds was associated with improved biocontrol activity against take-all disease of wheat, caused by Gaeumannomyces graminis var. tritici. This study provides new evidence for a close association of gluconic acid metabolism with antifungal compound production and biocontrol activity in P. fluorescens CHA0.
    Applied and environmental microbiology 05/2009; 75(12):4162-74. · 3.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Bioconversion of cassava-derived glucose to 2-keto-D-gluconic acid (2-KDG) using resting cells of immobilized Pseudomonas aeruginosa IFO 3448 was investigated. The tuberous roots of cassava were selected as the feedstock as they are inexpensive and widely available, and possess high amounts of starch (approximately 70% (w/w) of dry mass). Immobilized bacteria was used in a fed-batch fermenter and recycled over a period of 2 weeks. Given that the formation of 2-KDG from glucose requires oxygen as a reagent, and that high glucose concentrations are detrimental to the production yield of 2-KDG by resting cells, a DO-stat control strategy was used, whereby the feed rate of cassava hydrolysate was regulated by coupling it with the control variable, dissolved oxygen. For 319 h of operation including three cycles of repeated fed batch, 72 g of 2-KDG was produced from hydrolysate derived from 110 g of dried cassava at a maximum production rate of 0.55 g/L/h and an average concentration of 35 g/L.
    Applied Microbiology and Biotechnology 05/2008; 78(5):759-65. · 3.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Microbiological changes were studied in minced beef and minced dark, firm, dry (DFD) pork stored under different atmospheres (100% in carbon dioxide, nitrogen or air) at 3°C. The storage life (time for 100-fold increase in TVC) of samples flushed with carbon dioxide was increased by c. 3–4 days. Pseudomonads were the dominant organisms in samples stored in air, and lactic acid bacteria and Brochothrix thermosphacta in those stored under carbon dioxide. There was an alkaline drift in all samples, but at different rates (air > nitrogen > carbon dioxide). The rate of glucose assimilation in normal and DFD beef was slower in the samples stored under carbon dioxide than those under nitrogen or air. Lactate, gluconate, acetic acid, ethanol and diacetyl occurred in normal and DFD beef regardless of the storage atmospheres.
    International Journal of Food Science & Technology 06/2007; 25(4):389 - 398. · 1.24 Impact Factor

Full-text

View
0 Downloads
Available from