Carbon isotope-labelling experiments indicate that ladderane lipids of anammox bacteria are synthesized by a previously undescribed, novel pathway.
Ladderane lipids are unusual membrane lipids of bacteria that anaerobically oxidize ammonium to dinitrogen gas (anammox). Ladderane lipids contain linearly concatenated cyclobutane rings for which the pathway of biosynthesis is currently unknown. To investigate the possible biosynthetic routes of these lipids, 2-(13)C-labelled acetate was added to a culture of the anammox bacterium Candidatus Brocadia fulgida. Labelling patterns obtained by high-field (13)C nuclear magnetic resonance spectroscopy of isolated lipids indicated that C. Brocadia fulgida synthesizes C(16:0) and isoC(16:0) fatty acids according to the known pathway of type II fatty acid biosynthesis. The (13)C-labelling pattern of the C(8) alkyl chain of the C(20) [3] ladderane monoether also indicated the use of this route. However, carbon atoms in the cyclobutane rings and the cyclohexane ring were nonspecifically labelled and did not correspond to known patterns of fatty acid synthesis. Taken together, our results indicate that it is unlikely that ladderane lipids are formed from the cyclization of polyunsaturated fatty acids as hypothesized previously and suggest an alternative, although as yet unknown, pathway of biosynthesis.
Rattray
Jayne E
JE
Department of Marine Organic Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, Texel, The Netherlands.
Geenevasen
Jan A J
JA
van Niftrik
Laura
L
Rijpstra
W Irene C
WI
Hopmans
Ellen C
EC
Strous
Marc
M
Schouten
Stefan
S
Jetten
Mike S M
MS
Sinninghe Damsté
Jaap S
JS
D019342:Acetic Acid / Q000378:metabolism; D001419:Bacteria / Q000737:chemistry / Q000378:metabolism*; D053898:Biosynthetic Pathways; D002247:Carbon Isotopes / Q000378:metabolism*; D008055:Lipids / Q000096:biosynthesis*; D009682:Magnetic Resonance Spectroscopy
D002247:Carbon Isotopes; D008055:Lipids; D019342:Acetic Acid