Energy transduction in the mitochondrionlike bacterium Paracoccus denitrificans during carbon- or sulphate-limited aerobic growth in continuous culture

1978 ◽  
Vol 56 (1) ◽  
pp. 13-22 ◽  
Author(s):  
H. G. Lawford
Keyword(s):  
Growth Rate ◽  
Electron Transport ◽  
Continuous Culture ◽  
Respiratory Chain ◽  
Paracoccus Denitrificans ◽  
Proton Translocation ◽  
Short Interval ◽  
Specific Inhibitor ◽  
Growth Yield ◽  
Aerobic Growth

Paracoccus denitrificans was grown in carbon-limited aerobic continuous culture (critical dilution rate (Dc) = 0.48 h−1). The molar growth yield for carbon (succinate or malate) was constant at about 60 over a broad dilution range (growth rate) from 0.10 to 0.48 h−1. Measurements of the stoichiometry of proton translocation associated with the oxidation of endogenous substrates yielded a ratio of protons ejected from the cell per atom of oxygen consumed (→H+:O) of 8.55 which decreased to 5.85 in the presence of piericidin A (PA), a specific inhibitor of NADH dehydrogenase (EC 1.6.99.3). With starved cells, the observed →H+:O associated with the oxidation of added succinate in the presence of PA was 5.61. These observed →H+:O's represent an underestimation since no correction was made for proton backflow during the short interval of respiratory activity. Aerobic growth of Pc. denitrificans in the chemostat becomes sulphate limited at entering concentrations of sulphate <300 μM. Neither the maximum specific growth rate (measured at Dc) nor the observed molar growth yield for succinate decreased under sulphate limitation. The NADH oxidase in electron transport particles prepared from sulphate-limited cells was completely inhibited by PA. The stoichiometry of proton translocation associated with malate oxidation was similarly unaffected by sulphate limitation. It is concluded that (a) the respiratory chain of aerobic, heterotrophically grown Pc. denitrificans possesses three sites of energy conservation, including site III, (b) the number of protons ejected during the transfer of one pair of reducing equivalents along a region of the electron transport chain equivalent to a single energy-coupling site is 3, and (c) that sulphate limitation does not lead to a loss of proton translocation associated with the cytochrome-independent region of the respiratory chain.

scholarly journals Structure of the Zymomonas mobilis respiratory chain: oxygen affinity of electron transport and the role of cytochrome c peroxidase

Microbiology ◽  
2014 ◽  
Vol 160 (9) ◽  
pp. 2045-2052 ◽  
Author(s):  
Elina Balodite ◽  
Inese Strazdina ◽  
Nina Galinina ◽  
Samantha McLean ◽  
Reinis Rutkis ◽  
...  
Keyword(s):  
Electron Transport ◽  
Respiratory Chain ◽  
Peroxidase Activity ◽  
Zymomonas Mobilis ◽  
Alternative Oxidase ◽  
Oxygen Affinity ◽  
Aerobic Growth ◽  
Nadh Peroxidase ◽  
Kinetics Of

The genome of the ethanol-producing bacterium Zymomonas mobilis encodes a bd-type terminal oxidase, cytochrome bc 1 complex and several c-type cytochromes, yet lacks sequences homologous to any of the known bacterial cytochrome c oxidase genes. Recently, it was suggested that a putative respiratory cytochrome c peroxidase, receiving electrons from the cytochrome bc 1 complex via cytochrome c 552, might function as a peroxidase and/or an alternative oxidase. The present study was designed to test this hypothesis, by construction of a cytochrome c peroxidase mutant (Zm6-perC), and comparison of its properties with those of a mutant defective in the cytochrome b subunit of the bc 1 complex (Zm6-cytB). Disruption of the cytochrome c peroxidase gene (ZZ60192) caused a decrease of the membrane NADH peroxidase activity, impaired the resistance of growing culture to exogenous hydrogen peroxide and hampered aerobic growth. However, this mutation did not affect the activity or oxygen affinity of the respiratory chain, or the kinetics of cytochrome d reduction. Furthermore, the peroxide resistance and membrane NADH peroxidase activity of strain Zm6-cytB had not decreased, but both the oxygen affinity of electron transport and the kinetics of cytochrome d reduction were affected. It is therefore concluded that the cytochrome c peroxidase does not terminate the cytochrome bc 1 branch of Z. mobilis, and that it is functioning as a quinol peroxidase.

Proton translocation coupled to ubiquinol oxidation in Paracoccus denitrificans

1979 ◽  
Vol 57 (2) ◽  
pp. 172-177 ◽  
Author(s):  
Hugh G. Lawford
Keyword(s):  
Respiratory Chain ◽  
Oxidase Activity ◽  
Paracoccus Denitrificans ◽  
Electron Flow ◽  
Proton Translocation ◽  
Energy Coupling ◽  
Ubiquinol Oxidase ◽  
Transport Chain ◽  
Flow Through ◽  
Chemiosmotic Coupling

Measurements were made of the stoichiometry of proton translocation associated with electron flow through the cytochrome-dependent region of the aerobically induced respiratory chain of Paracoccus denitrificans using the pulse oxidant method and rotenone to inhibit NADH dehydrogenase activity. Paracoccus denitrificans (ATCC 13543) was grown aerobically in carbon-limited continuous culture D = 0.27 h−1D, dilution rate per hour) with succinate as sole carbon and energy source. Oxidation of exogenous ubiquinol1 by starved cells was significantly accelerated by treatment of the cells with lysozyme. Spectrophotometric assay of ubiquinol1 oxidase activity in rotenone-poisoned spheroplasts revealed an apparent Km of 25 μM and a Vmax of 217 nmol/min per milligram protein. In site 1 poisoned spheroplasts proton translocation was dependent on the presence of added respiratory substrate, either succinate or ubiquinol1, where the observed ratios of protons ejected from the membrane per atom of oxygen consumed (← H+: O) were 5.3 and 5.2 respectively. The rate of proton translocation associated with succinate and ubiquinol1 oxidation was significantly decreased in the presence of antimycin A and completely abolished with cyanide. Net proton translocation was not observed after the addition of uncoupler (CCCP). Assuming there are two potential sites of energy conservation associated with the region of the respiratory chain from ubiquinone to cytochrome oxidase (i.e., ubiquinol oxidase activity), then the number of protons ejected during the transfer of one pair of reducing equivalents along a region of the electron transport chain equivalent to a single energy-coupling or conservation site (← H+: site) ratio in P. denitrificans is closer to 3 than 2 as predicted by Mitchell's chemiosmotic coupling hypothesis.

CONTINUOUS CULTURE OF BRUCELLA ABORTUS S.19

1961 ◽  
Vol 7 (4) ◽  
pp. 491-505 ◽  
Author(s):  
Andreas H. W. Hauschild ◽  
Hilliard Pivnick
Keyword(s):  
Growth Rate ◽  
Continuous Culture ◽  
Dilution Rate ◽  
Brucella Abortus ◽  
Specific Growth ◽  
Limiting Factor ◽  
Continuous Growth ◽  
Viable Cells ◽  
Metabolic Products ◽  
Growth Of Bacteria

An apparatus is described for the continuous growth of bacteria. Brucella abortus S.19 has been grown in continuous culture for periods up to 3 weeks with populations up to 2 × 1011viable cells per ml and without the establishment of nonsmooth variants.Concentrations between 3 × 109and 2 × 1011cells per ml could be maintained as a function of the dilution rate without the requirement of a known limiting factor in the medium. In a series of steady-state conditions, the specific growth rate increased steadily up to 0.28 hour−1with decreasing population levels.Incidence of mutants was governed by the dilution rate and could also be reduced by various chelating substances.In continuous growth combined with continuous dialysis, population levels were approximately twice those obtained in continuous growth without dialysis. The effect of dialysis appears to be the continuous removal of growth-limiting metabolic products.

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