title: Occurrence of oleic and 18:1 methyl-branched acyl chains in lipids of Rhodobacter sphaeroides 2.4.1.
abstract: The fatty acids (FAs) composition of lipids extracted from Rhodobacter sphaeroides 2.4.1 was investigated by gas chromatography-mass spectrometry (GC-MS) analysis of the corresponding FA methyl esters (FAMEs), obtained through trans-esterification of the original lipid species. A GC stationary phase based on a highly polar ionic liquid (IL) was selected, aimed to enhance the separation of isomeric FAMEs with particular emphasis on positional and geometrical isomers of monounsaturated 16:1 and 18:1 fatty acyl chains. The occurrence of 18:1 cis-Δ(9) (oleic) acid, a positional isomer of the well-known and most predominant 18:1 cis-Δ(11) (cis-vaccenic) acid, has been demonstrated here for the first time. Furthermore a methyl branched 18:1 FA was also identified and its structure tentatively assigned as 11-methyl-Δ(12)-octadecenoic acid (most likely as trans isomer). The unprecedented observation about 18:1 cis-Δ(9) FA occurrence in R. sphaeroides 2.4.1 is, even indirectly, supported by a biosynthetic pathway postulated with the aid of the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. The concurrent presence of 16:1 cis-Δ(7) and 18:1 cis-Δ(9) FAs suggested the existence of parallel and/or complementary processes to those invoked for the formation of most common 16:1 cis-Δ(9) and 18:1 cis-Δ(11) FAs. A further route was hypothesized for the trans FAs biosynthesis in wild-type cells of R. sphaeroides.
authors.affiliation: Dipartimento di Chimica & Centro Interdipartimentale SMART, Università degli Studi di Bari Aldo Moro, Campus Universitario, Via E. Orabona, 4, 70125 Bari, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Granafei
authors.affiliation: Dipartimento di Chimica & Centro Interdipartimentale SMART, Università degli Studi di Bari Aldo Moro, Campus Universitario, Via E. Orabona, 4, 70125 Bari, Italy.
authors.forename: Ilario
authors.initials: I
authors.lastname: Losito
authors.affiliation: Dipartimento di Scienze del Farmaco e dei Prodotti per la Salute, Università degli Studi di Messina, viale Annunziata, 98168 Messina, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Salivo
authors.affiliation: Dipartimento di Scienze del Farmaco e dei Prodotti per la Salute, Università degli Studi di Messina, viale Annunziata, 98168 Messina, Italy.
authors.forename: Peter Q
authors.initials: PQ
authors.lastname: Tranchida
authors.affiliation: Dipartimento di Scienze del Farmaco e dei Prodotti per la Salute, Università degli Studi di Messina, viale Annunziata, 98168 Messina, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Mondello
authors.affiliation: Dipartimento di Chimica & Centro Interdipartimentale SMART, Università degli Studi di Bari Aldo Moro, Campus Universitario, Via E. Orabona, 4, 70125 Bari, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Palmisano
authors.affiliation: Dipartimento di Chimica & Centro Interdipartimentale SMART, Università degli Studi di Bari Aldo Moro, Campus Universitario, Via E. Orabona, 4, 70125 Bari, Italy. Electronic address: tommaso.cataldi@uniba.it.
authors.forename: Tommaso R I
authors.initials: TR
authors.lastname: Cataldi
mesh_terms: D005227:Fatty Acids / Q000032:analysis*; D008401:Gas Chromatography-Mass Spectrometry; D052578:Ionic Liquids / Q000737:chemistry; D008745:Methylation; D019301:Oleic Acid / Q000032:analysis; D012242:Rhodobacter sphaeroides / Q000737:chemistry*
chemical_list: D005227:Fatty Acids; D052578:Ionic Liquids; D019301:Oleic Acid
keywords: Bacterial biosynthetic pathways; Fatty acids; Gas chromatography–mass spectrometry; Ionic liquid capillary column; Methyl branched fatty acids; R. sphaeroides