The structure of lipid A from the marine γ-proteobacterium Pseudoalteromonas nigrifaciens IAM 13010 T that was prepared by hydrolysis of the corresponding lipopolysaccharide by acetic acid (1%) was determined by chemical analysis, 13 C NMR spectroscopy, and MALDI/TOF and LSIMS mass spectrometry. It was shown that lipid A is a β-1,6-bonded disaccharide of glucosamine that is substituted by two phosphoric acids (in the C1 and C4′ positions), two (R)-3-hydroxyalkanoic (normal and branched) acids with ester bonding (at the C3 and C3′-positions), and (R)-3-hydroxydodecanoic and (R)-3-dodecanoyloxydodecanoic acids (both with amide bonding at C2′ and C2, respectively). It was hypothesized that this type of structure is typical of lipid A from bacteria of the genus Pseudoalteromonas in general.Key words: marine gram-negative bacteria, Pseudoalteromonas nigrifaciens, LPS, lipid A, 13 C NMR spectroscopy, MALDI/TOF and LSIMS mass spectrometry.Gram-negative bacteria contain an unusual glycophospholipid called lipid A in addition to classical lipids constructed from glycerine.It is well-known that variations in the structure of lipid A are largely determined by the cultivation conditions of the microorganisms [1, 2]. Therefore, we supposed that marine bacteria, whose habitat is typically cold with high pressure and an elevated content of inorganic salts [3], could become a source of structural variants of lipid A that are interesting from a pharmacological viewpoint. However, information on the structure and biological activity of lipid A from marine gram-negative bacteria are available for a limited number of microorganisms [4][5][6].We studied the structure of lipid A from a bacterium of the genus Pseudoalteromonas, P. nigrifaciens IAM 13010 T . This is an aerobic, heterotrophic, gram-negative bacterium [7] and widely distributed obligate marine microorganism that is easily isolated from littoral waters and from the open sea and requires seawater in the growth medium.The most common method for preparing lipid A is hydrolysis by AcOH (1%) of lipopolysaccharide (LPS) [8], which is in turn obtained by extraction of defatted cells by hot aqueous phenol (45%) by the Westphal method [9]. Using this approach, lipid A was isolated from P. nigrifaciens and contained glucosamine (GlcN), phosphorus, and FA according to total chemical analysis.The principal FA were 3-hydroxydodecanoic (3-OH-12:0, 36.1 mass %), a part of which (3.4%) occurred as the iso-form; dodecanoic (12:0, 12.8%); 3-hydroxyundecanoic (3-OH-11:0, 7.9%); 3-hydroxytetradecanoic (3-OH-14:0, 6.2%); 3-hydroxytridecanoic (3-OH-13:0, 5.0%); and 3-hydroxydecanoic (3-OH-10:0, 2.6%). Thus, lipid A from P. nigrifaciens, like lipid A from other bacteria of this genus [10], is highly heterogeneous with respect to the composition of 3-hydroxyalkanoic acids.According to TLC, lipid A from P. nigrifaciens is a rather complex mixture of homologs with differing degrees of phosphorylation and acylation. This significantly complicates its further structural characterization. In order to ...
