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Lipopolysaccharide (LPS) is the major component of the outer leaflet of the outer membrane of Gram-negative bacteria. The LPS molecule is composed of two biosynthetic entities: the lipid A--core and the O-polysaccharide (O-antigen). Most biological effects of LPS are due to the lipid A part, however, there is an increasing body of evidence also with Yersinia indicating that O-antigen plays an important role in effective colonization of host tissues, resistance to complement-mediated killing and in the resistance to cationic antimicrobial peptides that are key elements of the innate immune system. The biosynthesis of O-antigen requires numerous enzymatic activities and includes the biosynthesis of individual NDP-activated precursor sugars in the cytoplasm, linkage and sugar-specific transferases, O-unit flippase, O-antigen polymerase and O-chain length determinant. Based on this enzymatic mode of O-antigen biosynthesis LPS isolated from bacteria is a heterologous population of molecules; some do not carry any O-antigen while others that do have variation in the O-antigen chain lengths. The genes required for the O-antigen biosynthesis are located in O-antigen gene clusters that in genus Yersinia is located between the hemH and gsk genes. Temperature regulates the O-antigen expression in Y. enterocolitica and Y. pseudotuberculosis; bacteria grown at room temperature (RT, 22-25 degrees C) produce in abundance O-antigen while only trace amounts are present in bacteria grown at 37 degrees C. Even though the amount of O-antigen is known to fluctuate under different growth conditions in many bacteria very little detailed information is available on the control of the O-antigen biosynthetic machinery.

Lipopolysaccharide, genetic, lipopolysaccharides, structure, core, genetics, role, strain, cell, molecular, biological, cell wall, biochemistry, PAGE, function, genus, bacteriophage, Yersinia, molecular genetics, Yersinia pestis, influence, Bacteriophages, growth, temperature

NCBI PubMed ID: 12756756
Publication DOI: 10.1007/0-306-48416-1_38
Publisher: Springer US.
Editors: Skurnik M, Bengoechea JA, Granfors K
Institutions: Department of Bacteriology and Immunology, Haartman Institute, University of Helsinki, Finland

Caulobacters are adherent prosthecate bacteria that are members of bacterial biofouling communities in many environments. Investigation of the cell surface carbohydrates produced by two strains of the freshwater Caulobacter crescentus, CB2A and CB15A, revealed a hitherto undetected extracellular polysaccharide (EPS) or capsule. Isolation and characterization of the EPS fractions showed that each strain produced a unique neutral EPS which could not be readily removed from the cell surface by washing. Monosaccharide analysis showed that the main CB2A EPS contained D-glucose, D-gulose, and D-fucose in a ratio of 3:1:1, whereas the CB15A EPS fraction contained D-galactose, D-glucose, D-mannose, and D-fucose in approximately equal amounts. Methylation analysis of the main CB2A EPS showed the presence of terminal glucose and gulose groups, 3-linked fucosyl, and two 3,4-linked glucosyl units, thus confirming the pentasaccharide repeating unit indicated by 1H nuclear magnetic resonance analysis. Similar studies of the CB15A EPS revealed a tetrasaccharide repeating unit consisting of terminal galactose, 4-linked fucosyl, 3-linked glucosyl, and 3,4-linked mannosyl residues. EPS was not detectable by thin-section electron microscopy techniques, including some methods designed to preserve or enhance capsules, nor was the EPS readily detected on the cell surface by scanning electron microscopy when conventional fixation techniques were used; however, a structure consistent with EPS was revealed when samples were prepared by cryofixation and freeze-substitution methods

exopolysaccharides, gulose, Caulobacter crescentus

NCBI PubMed ID: 1885545
Publication DOI: 10.1128/jb.173.18.5677-5684.1991
Journal NLM ID: 2985120R
Publisher: American Society for Microbiology
Institutions: Department of Chemistry, University of British Columbia, Vancouver, Canada, Department of Microbiology, University of British Columbia, Vancouver, Canada
Methods: 1H NMR, methylation, periodate oxidation, GC-MS, acid hydrolysis, GC, Smith degradation, methanolysis, enzymatic digestion, colorimetry, acetylation, SEC, reduction, cell growth, dialysis, phenol-sulfuric acid assay, SEM, derivatization, evaporation, TEM, centrifugation

exopolysaccharides, gulose, Caulobacter crescentus