Structure of the O-specific polysaccharide from Shewanella japonica type strain KMM 3299T containing the rare amino sugar Fuc4NAc

Total Synthesis of the Conjugation-Ready Tetrasaccharide Repeating Unit of Shewanella japonica Type Strain KMM 3299T

Here we report the first total synthesis of the conjugation-ready tetrasaccharide repeating unit of Shewanella japonica type strain KMM 3299T. The presence of rare deoxyamino sugars and installation of three consecutive 1,2-cis glycosidic linkages makes the synthesis formidable. The challenging late-stage oxidation was overcome by using a galacturonate donor. The total synthesis was completed via a longest linear sequence of 22 steps in an overall yield of 3.5% starting from d-mannose.

Structural Studies of the Lipopolysaccharide of Aeromonas veronii bv. sobria Strain K133 Which Represents New Provisional Serogroup PGO1 Prevailing among Mesophilic Aeromonads on Polish Fish Farms

In the present work, we performed immunochemical studies of LPS, especially the O-specific polysaccharide (O-PS) of Aeromonas veronii bv. sobria strain K133, which was isolated from the kidney of carp (Cyprinus carpio L.) during an outbreak of motile aeromonad infection/motile aeromonad septicemia (MAI/MAS) on a Polish fish farm. The structural characterization of the O-PS, which was obtained by mild acid degradation of the LPS, was performed with chemical methods, MALDI-TOF mass spectrometry, and ¹H and ¹³C NMR spectroscopy. It was revealed that the O-PS has a unique composition of a linear tetrasaccharide repeating unit and contains a rarely occurring sugar 2,4-diamino-2,4,6-trideoxy-D-glucose (bacillosamine), which may determine the specificity of the serogroup. Western blotting and ELISA confirmed that A. veronii bv. sobria strain K133 belongs to the new serogroup PGO1, which is one of the most commonly represented immunotypes among carp and trout isolates of Aeromonas sp. in Polish aquacultures. Considering the increase in the MAI/MAS incidences and their impact on freshwater species, also with economic importance, and in the absence of an effective immunoprophylaxis, studies of the Aeromonas O-antigens are relevant in the light of epidemiological data and monitoring emergent pathogens representing unknown antigenic variants and serotypes.

Structure of the O-specific polysaccharide of Aeromonas veronii bv. sobria strain Pt393 isolated from rainbow trout (Oncorhynchus mykiss), which contains a rarely occurring sugar 4-acetamido-4,6-dideoxy-d-galactose, tomosamine

The O-specific polysaccharide (OPS) was isolated from the lipopolysaccharide of Aeromonas veronii bv. sobria strain Pt393, which is pathogenic to the rainbow trout (Oncorhynchus mykiss), after mild acid hydrolysis followed by GPC. The high-molecular-weight OPS fraction was studied with chemical methods, mass spectrometry, and ¹H and ¹³C NMR spectroscopy techniques, including 2D ¹H,¹H COSY, TOCSY, NOESY, ¹H-detected heteronuclear ¹H,¹³C HSQC, and HMBC experiments. It was found that the O-specific polysaccharide was built of a tetrasaccharide repeating unit composed of α-GalpNAc, α-FucpNAc, β-QuipNAc, and α-Fucp4NAc (4-acetamido-4,6-dideoxy-d-galactose, tomosamine) residues. The following structure of the OPS of A. sobria strain Pt393 was established: →4)-α-d-GalpNAc-(1 → 3)-α-l-FucpNAc-(1 → 3)-β-d-QuipNAc-(1 → 3)-α-d-Fucp4NAc-(1→.

Structure of the O-Specific polysaccharide from Shewanella japonica KMM 3601 containing 5,7-Diacetamido-3,5,7,9-tetradeoxy-D-glycero-D-talo-non-2-ulosonic acid

Structure of the O-specific polysaccharide chain of the lipopolysaccharide (LPS) of Shewanella japonica KMM 3601 was elucidated. The initial and O-deacylated LPS as well as a trisaccharide representing the O-deacetylated repeating unit of the O-specific polysaccharide were studied by sugar analysis along with 1H and 13C NMR spectroscopy. The polysaccharide was found to contain a rare higher sugar, 5,7-diacetamido-3,5,7,9-tetradeoxy-D-glycero-D-talo-non-2-ulosonic acid (a derivative of 4-epilegionaminic acid, 4eLeg). The following structure of the trisaccharide repeating unit was established: →4)-α-4eLegp5Ac7Ac-(2→4)-β-D-GlcpA3Ac-(1→3)-β-D-GalpNAc-(1→.

Structural analysis of an unusual bioactive N-acylated lipo-oligosaccharide LOS-IV in Mycobacterium marinum

Although lipo-oligosaccharides (LOSs) are recognized as major parietal components in many mycobacterial species, their involvement in the host-pathogen interactions have been scarcely documented. In particular, the biological implications arising from the high degree of structural species-specificity of these glycolipids remain largely unknown. Growing recognition of the Mycobacterium marinum-Danio rerio as a specific host-pathogen model devoted to the study of the physiopathology of mycobacterial infections prompted us to elucidate the structure-to-function relationships of the elusive end-product, LOS-IV, of the LOS biosynthetic pathway in M. marinum. Combination of physicochemical and molecular modeling methods established that LOS-IV resulted from the differential transfer on the caryophyllose-containing LOS-III of a family of very unusual N-acylated monosaccharides, naturally present as different diastereoisomers. In agreement with the partial loss of pathogenecity previously reported in a LOS-IV-deficient M. marinum mutant, we demonstrated that this terminal monosaccharide conferred to LOS-IV important biological functions, including macrophage activating properties.

Molecular structure of endotoxins from Gram-negative marine bacteria: an update

Marine bacteria are microrganisms that have adapted, through millions of years, to survival in environments often characterized by one or more extreme physical or chemical parameters, namely pressure, temperature and salinity. The main interest in the research on marine bacteria is due to their ability to produce several biologically active molecules, such as antibiotics, toxins and antitoxins, antitumor and antimicrobial agents. Nonetheless, lipopolysaccharides (LPSs), or their portions, from Gram-negative marine bacteria, have often shown low virulence, and represent potential candidates in the development of drugs to prevent septic shock. Besides, the molecular architecture of such molecules is related to the possibility of thriving in marine habitats, shielding the cell from the disrupting action of natural stress factors. Over the last few years, the depiction of a variety of structures of lipids A, core oligosaccharides and O-specific polysaccharides from LPSs of marine microrganisms has been given. In particular, here we will examine the most recently encountered structures for bacteria belonging to the genera Shewanella, Pseudoalteromonas and Alteromonas, of the gamma-Proteobacteria phylum, and to the genera Flavobacterium, Cellulophaga, Arenibacter and Chryseobacterium, of the Cytophaga-Flavobacterium-Bacteroides phylum. Particular attention will be paid to the chemical features expressed by these structures (characteristic monosaccharides, non-glycidic appendages, phosphate groups), to the typifying traits of LPSs from marine bacteria and to the possible correlation existing between such features and the adaptation, over years, of bacteria to marine environments.