Improved procedure for the drying and storage of polyacrylamide slab gels

Phase variation of Coxiella burneti0i strain Priscilla: influence of this phenomenon on biochemical features of its lipopolysaccharide

During the phase variation of Coxiella burnetii, modifications in its lipopolysaccharide (LPS) component were investigated. The cloned phase I C. burnetii cells were passed serially in chicken embryo yolk sacs up to the egg passage (EP) 90. The LPSs from the cells in EPs 3, 12, 21, 40, 60, and 90 were all separated by steric exclusion chromatography into three major populations: the high, intermediate, and low molecular weight fractions, differing one from another in size and chemical composition. No noticeable shortening of the O-polysaccharide chains was observed in the LPSs isolated during the C. burnetii cultivation. However, a redistribution of the existing LPS populations has been observed due to an increasing prevalence of those cells in the whole cell population that express LPS molecules with truncated O-chains and those being of R-type. In the high and intermediate molecular weight LPS populations, virenose and dihydrohydroxystreptose are lost gradually with the progress in phase variation. This occurs more readily with the former sugar. At present, the molecular mechanisms influencing the LPS modifications during the C. burnetii phase variation remain unclear.

Physicochemical characterization of the endotoxins from Coxiella burnetii strain Priscilla in relation to their bioactivities

BACKGROUND

Coxiella burnetii is the etiological agent of Q fever found worldwide. The microorganism has like other Gram-negative bacteria a lipopolysaccharide (LPS, endotoxin) in its outer membrane, which is important for the pathogenicity of the bacteria. In order to understand the biological activity of LPS, a detailed physico-chemical analysis of LPS is of utmost importance.

RESULTS

The lipid A moiety of LPS is tetraacylated and has longer (C-16) acyl chains than most other lipid A from enterobacterial strains. The two ester-linked 3-OH fatty acids found in the latter are lacking. The acyl chains of the C. burnetii endotoxins exhibit a broad melting range between 5 and 25 degrees C for LPS and 10 and 40 degrees C for lipid A. The lipid A moiety has a cubic inverted aggregate structure, and the inclination angle of the D-glucosamine disaccharide backbone plane of the lipid A part with respect to the membrane normal is around 40 degrees. Furthermore, the endotoxins readily intercalate into phospholipid liposomes mediated by the lipopolysaccharide-binding protein (LBP). The endotoxin-induced tumor necrosis factor alpha (TNFalpha) production in human mononuclear cells is one order of magnitude lower than that found for endotoxins from enterobacterial strains, whereas the same activity as in the latter compounds is found in the clotting reaction of the Limulus amebocyte lysate assay.

CONCLUSIONS

Despite a considerably different chemical primary structure of the C. burnetii lipid A in comparison with enterobacterial lipid A, the data can be well understood by applying the previously presented conformational concept of endotoxicity, a conical shape of the lipid A moiety of LPS and a sufficiently high inclination of the sugar backbone plane with respect to the membrane plane. Importantly, the role of the acyl chain fluidity in modulating endotoxicity now becomes more evident.

Structural analyses of the lipopolysaccharides from Chlamydophila psittaci strain 6BC and Chlamydophila pneumoniae strain Kajaani 6

Lipopolysaccharides (LPSs) of Chlamydophila psittaci 6BC and Chlamydophila pneumoniae Kajaani 6 contain 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo), GlcN, organic bound phosphate, and fatty acids in the molar ratios of approximately 3:2:2.2:4.8 and approximately 2.9:2:2.1:4.9, respectively. The LPSs were immunoreactive with a monoclonal antibody against a family-specific epitope of chlamydial LPS. This finding, together with methylation analyses of both LPSs and MALDI-TOF MS experiments on de-O-, and de-O,N-acylated LPSs, indicate the presence of a Kdo trisaccharide proximal to lipid A having a structure alpha-Kdo-(2-->8)-alpha-Kdo-(2-->4)-alpha-Kdo, which appears to be the main component of the core region in the native chlamydial LPSs. In the de-O-acylated LPSs from Chl. psittaci 6BC and Chl. pneumoniae Kajaani 6, two major molecular species are present that differ in distribution of amide-bound hydroxy fatty acids over both GlcN. It appears that either two (R)-3-hydroxy-18-methylicosanoic acids or one (R)-3-hydroxy-18-methylicosanoic acid and one (R)-3-hydroxyicosanoic acid are attached to the GlcN residues. In contrast, the de-O-acylated LPS of Chl. psittaci PK 5082 contains one major molecular species that has two (R)-3-hydroxyicosanoic acid residues attached to two GlcN residues.

Structural study on a lipopolysaccharide from Coxiella burnetii strain Nine Mile in avirulent phase II

A lipopolysaccharide isolated from Coxiella burnetti strain Nine Mile in avirulent phase II contains in the lipid A proximal region D-mannose, D-glycero-D-manno-heptose, and 3-deoxy-D- manno-oct-2-ulosonic acid (Kdo) in the molar ratio 2:2:3. The primary structure 1 of the heptasaccharide was determined by glycose analysis, methylation analysis, ESI-MS, and FABMS. [sequence: see text]