02183naa a2200277 a 450000100080000000500110000800800410001910000160006024501240007626000090020052014010020965000110161065000220162165000120164365300080165565300060166365300210166965300170169065300160170765300080172365300390173165300150177070000190178570000200180477300810182416212372001-08-03       2000    bl ---       0--  u    #d1 aLUNA, M. F.  aThe carbon source influences the energetic efficiency of the respiratory chain of N2-fixing Acetobacter diazotrophicus.  c2000  aAcetobacter diazotrophicus is a diazotrophic bacterium that colonizes sugarcane tissues. Glucose is oxidized to gluconate in the periplasm prior to uptake and metabolism. A membrane-bound glucose dehydrogenase quinoenzyme [ which contains pyrroloquinoline quinone (PQQ) as the prosthetic group] is involved in that oxidation. Gluconate is oxidized further via the hexose monophosphate pathway and tricarboxylic acid cycle. A.diazotrophicus PAL3 was grown in a chemostat with atmospheric nitrogen as the sole N source provided that the dissolved oxygen was maintained at 1.0-2.0% air saturation. The biomass yields of A. diazotrophicus growing with glucose or gluconate with fixed N were very low compared with other heterotrophic bacteria. The biomass yields under N-fixing conditions were more than 30% less than with ammonium as the N source using gluconate as the carbon source but, surprisingly, were only about 14% less with glucose. The following scheme for the metabolism of A. diazotrophicus through the different pathways emerged: (1) the respiratory chain of this organism had a different efficiency of ATP production in the respiratory chain(P:o ratio) under different culture conditions; and (2) N fixation was one (but not the sole) condition under which a higher P:O ratio was observed. The other condition appears to be the expression of an active PQQ-linked glucose dehydrogenase.  acarbon  anitrogen fixation  aCarbono  aBNF  aC  aCana-de-açúcar  aDiazotrofico  aDiazotrophs  aFBN  aFixação biologica de nitrogênio  aSugar Cane1 aMIGNONE, C. F.1 aBOLAR DI, J. L.  tApplied and Environmental Microbiology, Washingtongv. 54, p. 564-569, 2000.