The efficiency of oxidative phosphorylation in symbiotic nitrogen-fixing bacteria of the genus Rhizobium in the root nodules of leguminous plants is of fundamental importance as it influences the efficiency of ATP generation from the oxidation of plant photosynthate for the ATP-dependent process of nitrogen fixation. A poor efficiency of energy coupling was found for Rhizobium leguminosarum grown glucose-limited in chemostat culture as indicated by low growth yields on glucose [Ymax glucose = 80·3 g dry wt bacteria (mol glucose)−1 and O2 [Ymax oxygen = 25·6 g dry wt bacteria (mol O2)−1. (These values are low when compared with those for aerobic heterotrophic bacteria which have two or three sites of oxidative phosphorylation.) Although H+/O measurements suggested a potential P/O ratio of 3 there was a very rapid rate of proton decay across the cell membrane; this coupled with the low growth yields suggested that the actual P/O ratio was nearer 1. Under conditions of excess dissolved oxygen cytochromes of the c, b, o and aa3 types were detected. Under oxygen limitation a d type terminal cytochrome oxidase was also produced and was associated with a further decrease in the efficiency of energy conservation. It remains to be seen whether such a low efficiency of energy conservation is expressed by R. leguminosarum within the root nodules of a host legume.
ApplebyC. A.,
TurnerG. L.,
MacnicolP. K.1975; Involvement of oxyhaemoglobin and cytochrome P-450 in an efficient oxidative phosphorylation pathway which supports nitrogen fixation in Rhizobium. Biochimica et biophysica acta 387:461–474
BergersenF. J.,
TurnerG. L.1975; Leghaemo- globin and the supply of O2 to nitrogen-fixing root nodule bacteroids: presence of two oxidase systems and ATP production at low free O2 concentration. Journal of General Microbiology 91:345–354
BergersenF. J.,
TurnerG. L.1980; Properties of terminal oxidase systems of bacteroids from root nodules of soybean and cowpea and of N2-fixing bacteria grown in continuous culture. Journal of General Microbiology 118:235–252
BergersenF. J.,
TurnerG. L.,
GibsonA. H.,
DudmanW. F.1976; Nitrogenase activity and respiration of cultures of Rhizobium spp. with special reference to concentration of dissolved oxygen. Biochimica et biophysica acta 444:164–174
DeansD. R.,
HuckleM. T.,
PetersonR. M.1971; A new column system for isothermal gas chromatographic analysis of light gases (H2,O2, N2, CO, CH4, C2H4, C2H5) employing a column switch technique. Chromatographia 4:279–285
FarmerI. S.,
JonesC. W.1976; The effect of temperature on the molar growth yield and maintenance requirement of Escherichia coli during aerobic growth in continuous culture. FEBS Letters 67:359–363
HerbertD.1976; Stoichiometric aspects of microbial growth. In Continuous Culture 6, Applications and New Fields pp. 1–30DeanA. C. R.,
EllwoodD. C.,
MellingH.
Edited by Chichester:: Ellis Horwood Publishers.;
De HollanderJ. A.,
BettenhaussenC. W.,
StouthamerA. H.1979; Growth yields, polysaccharide production and energy conservation in chemostat cultures of Rhizobium trifolii. Antonie van Leeuwenhoek 45:401–405
JonesC. W.,
BriceJ. M.,
DownsA. J.,
DrozdJ. W.1975; Bacterial respiration-linked proton translocation and its relationship to respiratory-chain composition. European Journal of Biochemistry 52:265–271
JonesC. W.,
BriceJ. M.,
EdwardsC.1977; The effect of respiratory chain composition on the growth efficiencies of aerobic bacteria. Archives of Microbiology 115:85–93
LaaneC.,
HaakerH.,
VeegerC.1978; Involvement of the cytoplasmic membrane in nitrogen fixation by Rhizobium leguminosarum bacteroids. European Journal of Biochemistry 87:147–153
LintonJ. D.,
HarrisonD. E. F.,
BullA. T.1975; Molar growth yields, respiration and cytochrome patterns of Beneckea natriegens when grown under different medium dissolved oxygen tensions. Journal of General Microbiology 90:237–246
PetersenJ. B.,
EvansH. J.1979; Phospho-enolpyruvate carboxylase from soybean nodule cytosol. Evidence for the isoenzymes and kinetics of the most active component. Biochimica et biophysica acta 567:448–452
SimpsonF. B.,
MaierR. J.,
EvansH. J.1979; Hydrogen-stimulated CO2 fixation and co-ordinate induction of hydrogenase and ribulose bisphosphate carboxylase in a H2 uptake positive strain of Rhizobium japonicum. Archives of Microbiology 123:1–8