Open AccessA proposed citramalate cycle for acetate assimilation in the purple non‐sulfur bacterium Rhodospirillum rubrum
Author(s) -
Ivanovsky Ruslan N,
Krasilnikova Ele,
Berg Ivan A
Publication year - 1997
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1997.tb12602.x
Subject(s) - rhodospirillum rubrum , glyoxylate cycle , isocitrate lyase , malate synthase , biochemistry , pyruvate carboxylase , bicarbonate , phototroph , rhodospirillaceae , rhodospirillales , fluoroacetate , chemistry , assimilation (phonology) , biology , metabolism , enzyme , photosynthesis , organic chemistry , linguistics , philosophy
During phototrophic growth on acetate and CO 2 Rhodospirillum rubrum 2R contained malate synthase but lacked isocitrate lyase. Acetate assimilation by R. rubrum cells was stimulated by pyruvate, propionate glyoxylate, CO 2 and H 2 . Acetate photoassimilation by R. rubrum cells in the presence of bicarbonate was accompanied by glyoxylate secretion, which increased after addition of fluoroacetate and decreased after addition of malonate. When acetyl‐CoA was incubated with pyruvate in cell‐free extracts, citramalate was formed. Citramalate was also formed from propionyl‐CoA and glyoxylate. The existence in R. rubrum of a CO 2 ‐dependent cyclic pathway of acetate oxidation to glyoxylate with citramalate as an intermediate is proposed. Inhibitor analysis of acetate and bicarbonate assimilation indicated that pyruvate synthase is not involved in acetate assimilation in R. rubrum . The possible anaplerotic sequences employed by R. rubrum during phototrophic growth on acetate are discussed.