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  • 1
    Electronic Resource
    Electronic Resource
    Growth yields and the efficiency of oxidative phosphorylation of Paracoccus denitrificans during two- (carbon) substrate-limited growth (1979)
    Springer
    Archives of microbiology 121 (1979), S. 213-223 
    Details
    ISSN: 1432-072X
    Keywords: Oxidative phosphorylation ; Chemostat culture ; Growth yield ; Mixed substrates ; Ribulose-bisphosphate cycle ; Cytochrome c ; Single cell protein ; Methanol ; Paracoccus denitrificans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Paracoccus denitrificans was grown aerobically during two-(carbon)substrate-limitation on mannitol and methanol in chemostat cultures. Theoretical growth parameters were calculated based on the presence of 2 or 3 sites in the electron-transport chain of Paracoccus denitrificans. Experimental growth parameters determined during two-(carbon)substrate growth were conform to the presence of 3 sites of oxidative phosphorylation, while cells grown only on mannitol possessed 2 sites. The maximum growth yield on adenosine triphosphate (ATP), corrected for maintenance requirements, determined in chemostat experiments in which the methanol concentration is less than 2.11 times the mannitol concentration was 8.6 g of biomass. When the methanol concentration was more than 2.11 times the mannitol concentration the maximum growth yield on adenosine triphosphate decreased due to the more energy consuming process of CO2-assimilation. Cells use methanol only as energy source to increase the amount of mannitol used for assimilation purposes. When the methanol concentration in chemostat experiments was more than 2.11 times the mannitol concentration, all mannitol was used for assimilation and excess energy derived from methanol was used for CO2-assimilation via the ribulose-bisphosphate cycle. The synthesis of ribulosebisphosphate carboxylase was repressed when the methanol concentration in chemostat experiments was less than 2.11 times the mannitol concentration or when Paracoccus denitrificans was grown in batch culture on both methanol and mannitol. When in chemostat experiments the methanol concentration was more than 2.11 times the mannitol concentration ribulose-bisphosphate carboxylase activity could be demonstrated and CO2-assimilation will occur. It is proposed that energy produced in excess activates or derepresses the synthesis of the necessary enzymes of the ribulose-bisphosphate cycle in Paracoccus denitrificans. Consequently growth on any substrate will be carbonas well as energy-limited. When methanol is present in the nutrient cells of Paracoccus denitrificans synthesize a CO-binding type of cytochrome c, which is essential for methanol oxidase activity. The reason for the increase in efficiency of oxidative phosphorylation from 2 to 3 sites is most probably the occurrence of this CO-binding type of cytochrome c in which presence electrons preferentially pass through the a-type cytochrome region of the electron-transport chain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425058
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  • 2
    Electronic Resource
    Electronic Resource
    Reconsideration of the efficiency of energy transduction in Paracoccus denitrificans during growth under a variety of culture conditions (1984)
    Springer
    Archives of microbiology 139 (1984), S. 344-350 
    Details
    ISSN: 1432-072X
    Keywords: Growth yields ; Paracoccus denitrificans ; Oxidative phosphorylation ; Chemostat ; Denitrification ; Proton translocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. Theoretical overall P/2e- ratios were calculated for growth of Paracoccus denitrificans under a variety of culture conditions on the basis of a growth model and recently published schemes of electron transport and associated proton translocation. 2. Experimental overall P/2e- ratios were calculated, using the specific rate of ATP synthesis determined in cultures grown under aerobic carbon source-limited conditions. 3. The experimental P/2e- was equal to the theoretical P/2e- for aerobic sulphate-limited growth with gluconate or succinate as carbon source, on the assumption that site 1 phosphorylation was completely absent. 4. The experimental and the theoretical P/2e- were similar for growth on nitrate as terminal electron acceptor and gluconate, mannitol or succinate as carbon source, on the assumption that nitrate enters the cell via the electroneutral nitrate-nitrite antiport system. 5. The experimental and theoretical P/2e- were similar for growth on nitrite as terminal electron acceptor and mannitol or succinate as carbon source. 6. The experimental P/2e- was substantially lower than the theoretical P/2e- for aerobic growth with nitrate as nitrogen source and gluconate or mannitol as carbon source. The amount of energy needed for assimilative reduction of nitrate to ammonia was calculated from this difference.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00408377
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  • 3
    Electronic Resource
    Electronic Resource
    Soil layer-specific variability in net nitrification and denitrification in an acid coniferous forest (2000)
    Springer
    Biology and fertility of soils 32 (2000), S. 427-434 
    Details
    ISSN: 1432-0789
    Keywords: Keywords Nitrification ; Denitrification ; Forest soil ; Spatial variation ; Nutrient cycling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  High spatial variation in nitrification potentials has been observed in forest soils, but explanations for this variability have remained speculative. In the present study we determined whether sample treatment, sample size, denitrification or small-scale variations in abiotic properties could explain spatial variation in nitrogen transformations in the organic horizon of a pine forest soil. Net nitrate production in homogenates of the organic horizon was extremely variable. Sample size (60–600 cm2) had no significant effect on nitrate production. In homogenised samples no increased nitrogen production was observed compared to intact incubated cores. High small-scale variation in nitrate production was observed in the litter (L) horizon. When this stratified L layer was subdivided, high net nitrate production was observed in moss (LM) and fragmented needles, whereas no net nitrate production was found in intact needles. The addition of acetylene, inhibiting nitrous oxide reductase, led to significant nitrous oxide production in the L layer. Low nitrous oxide production was found in the LM layer and none in the fragmentation layer. These results show that denitrification can explain part of the spatial variation and plays a major role in nitrogen transformations in the L layer. The relatively higher pH and the presence of fungi are suggested as factors responsible for high denitrification rates in the L layer. As a consequence homogenisation of the organic horizon could lead to highly variable nitrate production due to denitrifying activity from the needles being introduced into other layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740000274
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    Paper (German National Licenses)
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