title: Accumulation of novel glycolipids and ornithine lipids in Mesorhizobium loti under phosphate deprivation.
abstract: Glycolipids are found mainly in photosynthetic organisms (plants, algae, and cyanobacteria), Gram-positive bacteria, and a few other bacterial phyla. They serve as membrane lipids and play a role under phosphate deprivation as surrogates for phospholipids. Mesorhizobium loti accumulates different di- and triglycosyl diacylglycerols, synthesized by the processive glycosyltransferase Pgt-Ml, and two so far unknown glycolipids, which were identified in this study by mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy as O-methyl-digalactosyl diacylglycerol (Me-DGD) and glucuronosyl diacylglycerol (GlcAD). Me-DGD is a novel glycolipid, whose synthesis depends on Pgt-Ml activity and the involvement of an unknown methyltransferase, while GlcAD is formed by a novel glycosyltransferase encoded by the open reading frame (ORF) mlr2668, using UDP-glucuronic acid as a sugar donor. Deletion mutants lacking GlcAD are not impaired in growth. Our data suggest that the different glycolipids in Mesorhizobium can mutually replace each other. This may be an adaptation mechanism to enhance the competitiveness in natural environments. A further nonphospholipid in Mesorhizobium was identified as a hydroxylated form of an ornithine lipid with the additional hydroxy group linked to the amide-bound fatty acid, introduced by the hydroxylase OlsD. The presence of this lipid has not been reported for rhizobia yet. The hydroxy group is placed on the C-2 position of the acyl chain as determined by NMR spectroscopy. Furthermore, the isolated ornithine lipids contained up to 80 to 90% d-configured ornithine, a stereoform so far undescribed in bacteria.
authors.affiliation: Institute of Molecular Physiology and Biotechnology of Plants, University of Bonn, Bonn, Germany.
authors.forename: Hannah
authors.initials: H
authors.lastname: Diercks
authors.affiliation: Institute of Molecular Physiology and Biotechnology of Plants, University of Bonn, Bonn, Germany.
authors.forename: Adrian
authors.initials: A
authors.lastname: Semeniuk
authors.affiliation: Division of Bioanalytical Chemistry, Research Center Borstel, Leibniz Center for Medicine and Biosciences, Borstel, Germany.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Gisch
authors.affiliation: Division of Bioanalytical Chemistry, Research Center Borstel, Leibniz Center for Medicine and Biosciences, Borstel, Germany.
authors.forename: Hermann
authors.initials: H
authors.lastname: Moll
authors.affiliation: Division of Structural Biochemistry, Research Center Borstel, Leibniz Center for Medicine and Biosciences, Borstel, Germany.
authors.forename: Katarzyna A
authors.initials: KA
authors.lastname: Duda
authors.affiliation: Institute of Molecular Physiology and Biotechnology of Plants, University of Bonn, Bonn, Germany hoelzl@uni-bonn.de.
authors.forename: Georg
authors.initials: G
authors.lastname: Hölzl
mesh_terms: D000222:Adaptation, Physiological; D002462:Cell Membrane / Q000737:chemistry*; D006017:Glycolipids / Q000032:analysis*; D008055:Lipids / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D059128:Mesorhizobium / Q000737:chemistry* / Q000378:metabolism*; D009952:Ornithine / Q000031:analogs & derivatives* / Q000032:analysis; D010710:Phosphates / Q000378:metabolism*
chemical_list: D006017:Glycolipids; D008055:Lipids; D010710:Phosphates; C051524:ornithine containing aminolipid; D009952:Ornithine