Evidence for the presence of the reductive pentose phosphate cycle in a filamentous anoxygenic photosynthetic bacterium, Oscillochloris trichoides strain DG-6.
Studies on autotrophic CO2 fixation by the filamentous anoxygenic photosynthetic bacterium Oscillochloris trichoides strain DG-6 demonstrated that, unlike other green bacteria, this organism metabolized CO2 via the reductive pentose phosphate cycle. Both key enzymes of this cycle--ribulose-1,5-bisphosphate carboxylase/oxygenase and phosphoribulokinase--were detected in cell extracts. The main product of ribulose 1,5-bisphosphate-dependent CO2 fixation was 3-phosphoglyceric acid. KCN, which is known to be a competitive inhibitor of ribulose-1,5-bisphosphate carboxylase/oxygenase, completely inhibited the CO2 assimilation by whole cells as well as by cell extracts of O. trichoides. The 13C/12C carbon isotope fractionation during photoautotrophic growth of O. trichoides was -19.7/1000, which is close to that obtained for autotrophic organisms that use ribulose-1,5-bisphosphate carboxylase as the primary carboxylation enzyme. Cell extracts of O. trichoides contained all the enzymes of the tricarboxylic acid cycle except 2-oxoglutarate dehydrogenase. No activity of isocitrate lyase, a key enzyme of the glyoxylate shunt, was found in cell extracts of O. trichoides DG-6.
Ivanovsky
Ruslan N
RN
Department of Microbiology, Moscow State University, Moscow, 119899, Russia.
Fal
Yuri I
YI
Department of Microbiology, Moscow State University, Moscow, 119899, Russia.
Berg
Ivan A
IA
Department of Microbiology, Moscow State University, Moscow, 119899, Russia.
Ugolkova
Natalya V
NV
Department of Microbiology, Moscow State University, Moscow, 119899, Russia.
Krasilnikova
Elena N
EN
Department of Microbiology, Moscow State University, Moscow, 119899, Russia.
Keppen
Olga I
OI
Department of Microbiology, Moscow State University, Moscow, 119899, Russia.
Zakharchuc
Leonid M
LM
Department of Microbiology, Moscow State University, Moscow, 119899, Russia.
Zyakun
Anatolii M
AM
Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Pushchino, 142292, Russia.
D001419:Bacteria / Q000201:enzymology* / Q000254:growth & development; D002245:Carbon Dioxide / Q000378:metabolism*; D002250:Carbon Radioisotopes / Q000378:metabolism; D002952:Citric Acid Cycle; D010084:Oxidation-Reduction; D010427:Pentose Phosphate Pathway; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism*
D002250:Carbon Radioisotopes; D002245:Carbon Dioxide; D017853:Phosphotransferases (Alcohol Group Acceptor); C022390:phosphoribulokinase; D012273:Ribulose-Bisphosphate Carboxylase