We now report that an acidic O-specific polysaccharide, obtained by mild acid degradation of the F.. maritimus LPSwas found to be composed of a disac-charide repeating unit built of 2-ace
Trang 1Structure of the polysaccharide chain of the lipopolysaccharide
Evgeny Vinogradov1, Leann L MacLean1, Elizabeth M Crump2, Malcolm B Perry1and William W Kay2
1
Institute for Biological Sciences, National Research Council, Ottawa, Ontario, Canada;2Department of Biochemistry and
Microbiology, University of Victoria, Victoria, British Columbia, Canada
Flexibacter maritimus, a Gram-negative bacterium, is a fish
pathogen responsible for disease in finfish species and a cause
of cutaneous erosion disease in sea-caged salmonids For the
development of serology based diagnostics, protective
vac-cines, and a study of pathogenesis, the structural analysis of
the lipopolysaccharide (LPS) produced by the bacterium has
been undertaken We now report that an acidic O-specific
polysaccharide, obtained by mild acid degradation of the
F maritimus LPSwas found to be composed of a
disac-charide repeating unit built of 2-acetamido-3-O-acetyl-4-[(S)-2-hydroxyglutar-5-ylamido]-2,4,6-trideoxy-b-glucose and 5-acetamido-7-[(S)-3-hydroxybutyramido]-8-amino-3,5,7,8,9-pentadeoxynonulopyranosonic acid (Sug) having the structure:
The configuration of the C-2–C-7 fragment of the latter monosaccharide (B) was assigned b-manno; however, the configuration at C-8 could not be established NMR data indicate that the two monosaccharides have opposite abso-lute configurations The repeating unit includes a linkage via
a (S)-2-hydroxyglutaric acid residue, reported here for the first time as a component of a bacterial polysaccharide The LPSwas also found to contain a minor amount of a disac-charide b-Sug-(2-3)-L-Rha, isolated from the products of the acidic methanolysis of the LPS
Keywords: Flexibacter maritimus; lipopolysaccharide; NMR; polysaccharide
The Cytophaga) Flavobacterium ) Flexibacter bacteria
are a large, somewhat heterogeneous group of filamentous,
gliding, Gram-negative bacteria with unusual surface
pro-perties [1] At least seven members of this group are
considered to be important fish pathogens They infect a
wide variety of fish species and usually form filamentous
biofilms, primarily on the tissues associated with the oral
cavity Among these, Flexibacter maritimus has recently
emerged as a cause of widespread severe mortality and
economic losses in farmed marine species worldwide [2]
F maritimus, a long rod-shaped, Gram-negative
bacter-ium, has been associated with disease (Flexibacteriosis) in a
number of fish species [3–5] and its economic importance
has been related to a cause of cutaneous erosion disease
particularly in sea-caged salmonids [6,7] In grouper,
F maritimuscauses red boil disease [8] related to its clinical
signs of reduced scales and severe hemorrhage on the body
surface, resembling boiled skin and causing a high mortality
rate No effective vaccine has been developed against this pathogen
A clearer definition of the relevant immunoreactive macromolecules of these bacterial fish pathogens is funda-mentally important particularly with regard to the mecha-nisms of pathogenesis and the role of infective biofilms This information is important for the development of appropri-ate immunochemical reagents to facilitappropri-ate speciation and the design of cost-effective, efficacious vaccines
Lipopolysaccharides (LPS, endotoxins) play a role in the pathogenesis of Gram-negative infections and the structural analysis of their antigenic LPSO-polysaccharide (O-PS) components is important in providing a molecular level understanding of their serological specificities, role in pathogenesis, development of diagnostic agents, and the production of O-PSbased conjugate vaccines As part of a study of bacterial fish infections, this paper records the determination of the unusual structure of the LPSO-PS-antigen of F maritimus
Experimental procedures
Bacterial cell growth and LPS and O-PS production
F maritimus was grown in a 35-L Chemap fermenter (Chemap AG, Volketswil, Switzerland) in 30 L MAT made
in an Instant Ocean (Aquarium Systems, Mentor, OH, USA)
at 25C, stirring at 300 r.p.m., aeration rate of 15 LÆmin)1, for 42 h Cells were collected by low speed centrifugation and
Correspondence to M B Perry, Institute for Biological Sciences,
National Research Council, Ottawa, Ontario, Canada K1A 0R6.
Fax: + 1 613 941 1327, Tel.: + 1 613 990 0837.
E-mail: Malcolm.Perry@nrc.ca
Abbreviations: LPS, lipopolysaccharide; O-PS, O-polysaccharide;
S-LPS, smooth LPS; R-LPS, rough LPS; DOC/PAGE, deoxycholate
polyacrylamide gel electrophoresis.
(Received 6 November 2002, revised 13 February 2003,
accepted 26 February 2003)
Trang 2the cell pellet (355 g) was washed with 0.9% NaCl and
extracted with stirred 50% aqueous phenol (400 mL) for
10 min at 60–70C Following low speed centrifugation of
the cooled (4C) extract to remove solid material, the clear
phenol and water phases were collected separately and
dialysed against running tap water until they were free from
phenol The lyophilized retentates were dissolved in 35 mL
10 mMTris pH 8.0 and treated sequentially with DNase and
RNase for 3 h at 37C, followed by proteinase K (Sigma) for
a further 6 h The digests were dialysed against distilled water
and ultracentrifuged at 105 000 g (4C) for 10 h to yield
LPSas gel pellets (yields: 910 mg water phase, 290 mg PhOH
phase) which were dissolved in distilled water and
lyophi-lized DOC/PAGE (13%) revealed that the water phase
extract contained essentially smooth LPS (S-LPS) and the
phenol phase rough LPS(R-LPS)
Aqueous phase S-LPS (0.4 g) in 2% (v/v) acetic acid
(100 mL) was kept at 100C for 2 h and following low
speed centrifugation to remove precipitated Lipid A
(61 mg), the lyophilized centrifugate dissolved in pyridinium
acetate buffer (pH 4.5, 5 mL), was fractionated by
Sepha-dex G-50 column chromatography (2.5· 90 cm) using the
same buffer as the eluant The high molecular mass O-PS
fraction (Kav, 0.02–0.15) of the eluant was lyophilyzed
(218 mg) The O-PShad [a]D)60 (c 0.2, water) and was
used in all further analyses
NMR spectroscopy and general methods
1H and13C NMR spectra were recorded on a Varian Inova
500 spectrometer in D2O at 25C with acetone standard
(2.225 p.p.m for 1H and 31.5 p.p.m for 13C) using
standard pulse sequences COSY, TOCSY (mixing time
120 ms), NOESY (mixing time 250 ms), HSQC, gHMBC
(optimized for 5 Hz long range coupling constant) GLC,
GLC-MS, electrospray MS, monosaccharide and chemical
analyses were performed as previously described [9]
Preparation of oligosaccharides 1 and 3
O-PS(60 mg) or LPS(200 mg) were suspended in dry
methanol (3 or 6 mL, respectively), cooled in a dry ice/
acetone bath, and acetyl chloride (0.2 or 0.4 mL) was added
and the dissolved material were kept at 80C for 24 h
Followed by drying in an air stream, the products were
separated by HPLC on a C18 column (Phenomenex Aqua,
0.9· 25 cm) in 2% MeCN in water Compound 3 was eluted
ahead of compound 1 (from LPS), the a- and b-anomers of 1
were not separated under these conditions: Yield of 1, 23 mg
from O-PS, 38 mg from LPS; yield of 3, 3 mg from LPS
The acetate derivative 2 was prepared by treatment of 1
(60 mg) with Ac2O/Py (1 : 1 v/v, 6 mL) at 100C for 1 h,
concentration by drying under air flow, and fractionation
on the HPLC system described using a 10–100% MeCN
gradient to yield 2 (56 mg)
Characterization of (S )-3-hydroxybutanoic acid
and (S )-2-hydroxyglutaric acid substituents
O-PS(15 mg) was hydrolysed with 2M HCl (0.2 mL,
100C, 4 h), and, after concentration in a nitrogen stream,
the solution of the residue in water was passed through
Dowex (H+) 50 W· 8–200 ion-exchange resin to remove basic materials and the concentrated eluate was subjected to
1H NMR identification and analysis according to the directions of the Sigma b-hydroxybutyrate dehydrogenase diagnostic system kit (procedure no 310 UV) [10] (S)-2-hydroxyglutaric acid released by methanolysis (M MeOH/ HCl, 100C, 16 h) and characterized by GLC of its O-trimethylsilylated (S)-2-butyl ester derivative as described previously [11,12] Authentic standards of optically active acids were from Sigma
Results and discussion
Fermenter grown cells of F maritimus were extracted by hot aqueous phenol and yielded S-LPS and R-LPS, obtained as precipitated gels after ultracentrifugation of the aqueous and phenol phases respectively DOC/PAGE analysis showed the S-LPS product to give silver stained ladder bands indicative of the LPSbeing composed of disaccharide repeating units forming a high molecular mass O-PSof a restricted mass range [13]
The O-PSwas isolated from the S-LPSof F maritimus by mild acid hydrolysis followed by Sephadex G50 gel-filtration chromatography No monosaccharides were iden-tified by GLC analysis of reduced and acetylated products from the use of conventional acid hydrolysis conditions NMR analysis of the polysaccharide using 1H, 13C, 2D-COSY, TOCSY, NOESY, HSQC, HSQC-TOCSY, and HMBC spectra led to the complete assignment of all
1H and13C signals and observed correlations, as presented
in Table 1 These data revealed the presence of the spin systems of 2,4-diacylamino-2,4,6-trideoxy-b-glucopyranose (A), 3-hydroxybutyrate (Bu), 2-hydroxyglutarate (C), and 5,7,8-triamino-3,5,7,8,9-pentadeoxynonulosonic acid (B) The positions of the amino groups were determined from the chemical shifts of the carbon atoms linked to nitrogen at 46.5–56.3 p.p.m (Fig 1) The position of N- and O-acyl groups was determined from three experiments: (a) in the HMBC spectrum, the carboxyl carbon of each acyl group gave a cross peak with the proton at the acylation position; (b) the H-2 (H-4 in case of 2-hydroxyglutaric acid residue) of the acyl residues gave a NOE to the respective protons at the acylation position; (c) NOEs measured in 9 : 1 H2O/D2O solution showed correlations between the amide protons and H-2 of acyl groups (Fig 2) Additionally, O-acetylation at O-3 residue A is supported by the low field position of A-31H signal at 5.02 p.p.m Pyranosidic ring size of residues A and B follows from the absence of other possibilities for ring size The b-gluco-configuration of residue A followed from measured vicinal coupling constants (Table 1) The confi-guration of the nonulosonic acid residue B was determined
on the basis of interproton coupling constants and NOE data The orientation of the substituents at C-4 and C-5 of residue B follows from measured coupling constants: a large coupling 13 Hz between H-3ax and H-4 indicated the axial position of H-4 Small coupling constants J4,5 and J5,6< 5 Hz indicated an equatorial orientation of H-5 A large coupling J6,7¼ 10.2 Hz corresponds to a trans-orientation of the H-6 and H-7 protons A strong NOE observed between NH-7 and H-5 is only possible in the case of a manno-configuration of the C-4–C-7 fragment,
as confirmed by molecular modelling
- FEBS2003 Polysaccharide structure of F maritimus LPS(Eur J Biochem 270) 1811
Trang 3(MSI-Accelrys) Futher NOEs observed between NH-5 and
H-3ax, and between NH-5 and H-7, were also consistent in
molecular modelling of the monosaccharide having a
manno-configuration Data establishing the configuration
at C-8 was not obtained
The anomeric configuration of the nonulosonic acid (B)
was deduced from the position of the H-3 proton signals As
shown previously for nonulosonic acids with the
manno-configuration of the C-4–C-7 fragment, the chemical shift of
the H-3eq signal > 2.5 p.p.m corresponded to an axial
orientation of the C-1 carboxyl group, and thus to the
b-configuration assigned [14]
The sequence of the component glycose residues were
determined from NOE and HMBC data The H-1 of
residue A gave a NOE to H-4 and a HMBC correlation to
C-4 of residue B, thus proving the linkage of A-(1–4)-B
HMBC correlation between C-2 of the nonulosonic
acid residue B and the H-2 of the 2-hydroxyglutaric acid
(residue C) indicated that residue B glycosylates C at the O-2 position
The13C NMR chemical shift of the C-1 of residue A had the same value ( 100 p.p.m) as that previously published for C-1 of b-D-QuiNAc in the b-D -QuiNAc-(1–4)-5-acet-amido-7-formamido-3,5,7,9-tetradeoxy-L-glycero-a-L -manno-nonulosonic acid fragment in the polysaccharide from Pseudoalteromonas distincta[15] This parameter is sensitive
to the combination of the absolute configurations of both monosaccharides, and in the case of the Ps distincta polysaccharide it reflects different configurations of the monosaccharides The A-B-fragment of the O-PSfrom
F maritimusis isosteric to that of Ps distincta in the vicinity
of this glycoside bond and therefore must follow the same rules for glycosylation effects Thus it can be concluded that residues A and B have different absolute configurations (in the case of nonulosonic acid the absolute configuration
is referenced to C-7, the last chiral centre of the
Table 1. 1H and13C-NMR Chemical shift and couplingdata for the F maritimus O-PS OMe at B1 in 1, 3.91/56.0 p.p.m.; in 2, 3.83/54.0; in 3, 3.88/ 55.8.
Residue Nucleus
1
J 1,2
(J 3ax,3eq )
2 (3ax)/NH
J 2,3
(J 3ax,4 )
3 (3eq)
J 3,4
(J 3eq,4 )
4/NH
J 4,5
5/NH
J 5,6
6
J 6,7
7/NH
J 7,8
8/NH
J 8,9 9
A, PS 1H 4.76 3.81/7.62 5.02 3.72/8.06 3.73 1.24
13
C 100.0 55.3 74.6 56.3 71.8 18.1
A, 1 1 H 4.99 3.40 3.86 3.66 3.87 1.21 OMe 3.44
13
A, 2 1H 4.68 4.33/6.32 5.15 3.85/6.99 3.93 1.25 OMe 3.34
B, PS 1H 1.82 2.64 3.98 4.32/8.38 4.01 4.15/8.11 3.59/7.82 1.31
13
C 173.4 103.6 36.0 74.2 46.5 74.2 51.7 50.3 14.5
J, Hz 12.8 12.8 < 3 < 3 < 3 10.2 8.5 6.5
B, 1 1H 1.89 2.74 4.14 3.54 4.08 4.45 3.61 1.41
13
C 170.6 102.5 35.7 64.6 51.8 72.4 51.7 48.9 12.9
J, Hz 13.4 13.4 5.0 3.8 0 10.7 2.7 6.9
B, 2 1H 1.84 2.39 4.84 4.45/6.85 3.78 4.34/6.24 4.37/6.61 1.17
13
C 168.7 100.4 31.5 68.8 45.5 74.0 52.4 47.0 15.6
B, 3 1H 1.83 2.80 4.14 3.54 3.92 4.43 4.03 1.41
13 C 170.9 100.3 35.9 64.7 51.8 72.3 52.0 49.3 13.6
13 C 179.1 75.5 30.0 32.6 177.0
13
D, 3 1H 4.64 3.63 4.13 3.51 3.72 1.30 OMe 3.38
13
Bu, PS 1 H 2.34; 2.43 4.18 1.22
13 C 175.4 46.3 66.0 23.3
Bu, 1 and 3 1H 2.46; 2.59 4.25 1.24
13 C 178.9 46.3 67.0 24.3
13
C 171.1 44.6 68.9 21.2
N-Ac at A2 1 H 1.93
13 C 175.4 23.4
O-Ac at A3 1H 2.01
13 C 174.5 21.2
N-Ac at B7 1 H 1.97
13
C 23.2 175.4
Trang 4manno-fragment) Since the residue of
2,4-diamino-2,4,6-trideoxyglucose (bacillosamine) has only been
found in theD-configuration [9,16–20], we tentatively present
it asD-, and therefore the nonulosonic acid derivative B in
theL-configuration
Acidic methanolysis of the O-PSgave a high yield of
disaccharide 1 (isolated by reverse-phase HPLC, it contained
20% b-anomer) NMR analysis showed 1 to represent the
repeating unit of the O-PSlacking both N-acetyl and
O-acetyl substituents Its structure was confirmed by
elec-trospray MSdata ([M + 2]2+ion at m/z 326.8) Complete
acetylation of 1 gave derivative 2, prepared pure in a
significant amount ( 50 mg) (the b-anomer was removed
at this stage by HPLC) in the unrealized, but expected hope
of obtaining crystals for the determination of the
configur-ation of Sug by X-ray diffraction
The absolute configuration of (S)-2-hydroxyglutarate was determined by GLC of its O-trimethylsilylated 2-butyl ester derivatives prepared with optically pure 2-(S)-butanol, and the absolute configuration of the (S)-3-hydroxybutyrate substituent was established from the negative reaction of the liberated acid in the enzymic
D-3-hydroxybutyric dehydrogenase analytical procedure [10]
The combined experimental data led to the following structure of the O-PSrepeat unit:
Acidic methanolysis of intact LPSgave, in addition to disaccharide 1, a minor amount of disaccharide 3 in which the nonulosonic acid residue was linked to the O-3 position of a rhamnose unit This product originated from the LPScore or was present as a single unit lost from the O-PSduring mild hydolysis LPSshowed the presence of Rha in a similar amount to those of GlcN, Glc and Man: each of these monosaccharide constituted 0.5–1.5% by weight of the LPS Rhamnose was not present in the isolated O-PS
Fig 1.1H-13C HSQC spectrum of F maritimus O-PS The anomeric signal of residue A in the1H NMR spectrum resides under the water signal.
FEBS2003 Polysaccharide structure of F maritimus LPS(Eur J Biochem 270) 1813
Trang 5Nonulosonic acids have been found in natural
sources in three major variants:
5-amino-3,5-dideoxy-D-glycero-D-galacto-nonulosonic acid (neuraminic acid),
3-deoxy-D-glycero-D-galacto-nonulosonic acid (Kdn) and
5,7-diamino-3,5,7,9-tetradeoxy-nonulosonic acids The
latter class was found in four configurations: L
-glycero-L-manno (pseudaminic acid), D-glycero-D-galacto
(legio-naminic acid), L-glycero-D-galacto (8-epi-legionaminic
acid), and D-glycero-D-talo (4-epilegionaminic acid)
[12,21] All of these monosaccharides can have variable
N- and O-acyl substituents and other modifications
O-PSfrom Flexibacter, described herein, contains a new
nonulosonic acid derivative,
5-(3-hydroxybutyramido)-7-
acetamido-8-amino-3,5,7,8,9-pentadeoxy-b-manno-nonulo-pyranosonic acid, with as yet undetermined configuration
at C-8 and tentatively assigned the L-absolute configur-ation Biosynthesis of sialic acids and possibly 5,7-diamino-3,5,7,9-tetradeoxy-nonulosonic acids proceeds
by condensation of hexose derivatives with phosphoenol-pyruvate, so that atoms C1–C6 of the hexose become C4–C9 of the nonulosonic acid As in the 5,7,8-triamino-3,5,7,8,9-pentadeoxynonulopyranosonic acid position 8, which would be C-5 in a possible hexose precursor, is occupied by an amino group, its biosynthesis must be different from that of other nonulosonic acids or include
an introduction of the amino group following the condensation step
The O-PSof F maritimus contains a linkage involving a (R)-2-hydroxyglutaric acid residue reported here for the first time as a bacterial polysaccharide component A similar component, O-glycosylated amide linked (R)-malic acid was recently reported as a component of the O-PSfrom another fish pathogen Flavobacterium psychrophilum [9]
The structural differences exhibited by the O-PSs from
F maritimusand Fl psychrophilum [9] are reflected in the observed serological specificities shown by rabbit antisera prepared against synthetic respective O-PSglycoconjugates (unpublished data) and their use as diagnostic agents and
Fig 2 Partial NOESY spectrum of F maritimus O-PS (H 2 O/D 2 O, 9 : 1) showingcorrelations from NH-protons.
Trang 6possible vaccines It is also interesting that the prolific
production of the O-PSof these species probably
contri-butes to the surface properties and consequent biofilming
characteristics of these pathogens, especially in the case of
F maritimus
Acknowledgements
This work was supported by the Canadian Bacterial Diseases Network.
References
1 Bernadet, J.F., Segers, P., Vancanneyt, M., Berthe, F.,
Kersters, K & Vandamme, P (1996) Cutting the Gordian knot:
emended classification and description of the genus
Flavobacter-ium, emended description of the family Flavobacteriaceae, and
proposal of Flavobacterium hydatis nom nov, (Basonym,
Cyto-phaga aquatalis Strohl and Tait (1978) Int J Syst Bacteriol 46,
128–148.
2 Bernadet, J.F (1997) Immunization with bacterial antigens:
Flavobacterium and Flexibacterium infections Dev Biol Stand 90,
179–188.
3 Handlinger, J., Soltani, M & Percival, S (1997) The pathology of
Flexibacter maritimus in aquaculture species in Tasmania,
Aus-tralia J Fish Dis 20, 159–169.
4 Soltani, M., Munday, B.L & Burke, C.M (1996) The relative
susceptibility of fish to infections by Flexibacter columnaris and
Flexibacter maritimus Aquaculture 410, 259–264.
5 Wakabayashi, H., Hikida, M & Masumura, K (1984) Flexibacter
infection in cultured marine fish in Japan Helgolander
Meere-sunters 37, 587–593.
6 S chmidtke, L., Carson, J & Howard, T (1991) Maine Flexibacter
infection in Atlantic salmon Characterization of the putative
pathogen In Proceedings of the SALTAS Research Review
Seminar, pp 25–39 Hobart, Tasmania 22nd May 1991 Salmon
Enterprises of Tasmania (SALTAS) P/L, Hobart, Tasmania.
7 Danayadol, Y., Krachalwong, V., Ruangpan, L &
Direkbusar-akom, S (1996) Causative agent and control measure of red boil
disease in cultured grouper (Epinephelus malabaricus) Thai
Fish-eries Gazette 48, 29–35.
8 Ostland, V.E., LaTrace, C., Morrison, D & Ferguson, H.W.
(1999) Flexibacter maritimus associated with bacterial stomatitis in
Atlantic salmon smolts reared in net-pens in, British Columbia.
J Aquatic Health 11, 35–45.
9 MacLean, L.L., Vinogradov, E., Crump, E.M., Perry, M.B &
Kay, W.W (2001) The structure of the lipopolysaccharide
O-antigen produced by Flavobacterium psychrophilum (259–93).
Eur J Biochem 268, 1–8.
10 Williamson, D.H., Mellanby, J & Krebs, H.A (1962) Enzymic
determination of D -(-)-b-hydroxybutyric acid and acetoacetic acid
in blood Biochem J 82, 90–96.
11 Shashkov, A.S., Paramonov, N.A., Veremeychenko, S.P., Grosskurth, H., Zdorovenko, G.M., Knirel, Y.A & Kochet-kov, N.K (1998) Somatic antigens of pseudomonads: Structure
of the O-specific polysaccharides of Pseudomonas fluorescens biovar B strain IMV 247 Carbohydr Res 306, 297–303.
12 Perepelov, A.V., Babicka, D., Senchenkova, S.N., Shashkov, A.S., Moll, H., Rozalski, A., Za¨hringer, U & Knirel Y.A (2001) Structure of the O-polysaccharide of Proteus vulgaris O4 con-taining a new component of bacterial polysaccharides, 4,6-di-deoxy-4-{[N-[(R)-3-hydroxybutyryl]- L -alanyl}amino- D -glucose Carbohydr Res 331, 195–202.
13 Perry, M.B & Babiuk, L.A (1983) Structure of the polysaccharide chains of Pasteurella haemolytica (serotype 4) lipopolysaccharide Can J Biochem Cell Biol 62, 108–114.
14 Tsvetkov, Y.E., Shashkov, A.S., Knirel, Y.A & Za¨hringer, U (2001) Synthesis and NMR spectroscopy of nine stereoisomeric 5,7-diacetamido-3,5,7,9-tetradeoxynon-2-ulosonic acids Carbo-hydr Res 335, 221–243.
15 Muldoon, J., Shashkov, A.S., Senchenkova, S.N., Tomshich, S.V., Komandrova, N.A., Romanenko, L.A., Knirel, Y.A & Savage, A.V (2001) Structure of the acidic polysaccharide from a marine bacterium Pseudoalteromonas distincta KMM 638 containing 5-acetamido-3,5,7,9-7-formamido- L -glycero- L -manno-nonulosonic acid Carbohydr Res 330, 231–239.
16 Hermansson, K., Perry, M.B., Altman, E., Brisson, J.-R & Garcia, M.M (1993) Structural studies of the O-antigenic polysaccharide
of Fusobacterium necrophorum Eur J Biochem 212, 801–809.
17 Chowdhury, T.A., Jansson, P.E., Lindberg, B., Gustafsson, B & Holme, T (1991) Structural studies of Vibrio cholerae O: 3 O-antigen polysaccharide Carbohydr Res 215, 303–314.
18 Knirel, Y.A., Vinogradov, E.V., Shashkov, A.S., Wilkinson, S.G., Tahara, Y., Dmitriev, B A., Kochetkov, N.K., Stanislavsky, E.S.
& Mashilova, G.M (1986) Somatic antigens of Pseudomonas aeruginosa The structure of O-specific polysaccharide chains of the lipopolysaccharides from P aeruginosa O1 (Lanyi), O3 (Habs), O13 and O14 (Wokatsch), and serologically related strains NCTC 8505 Eur J Biochem 155, 659–669.
19 Zubkov, V.A., Nazarenko, E.L., Gorshkova, R.P., Ivanova, E.P., Shashkov, A.S., Knirel, Y.A., Paramonov, N.A & Ovodov, Y.S (1995) Structure of the capsular polysaccharide from Alteromonas
sp CMM 155 Carbohydr Res 275, 147–154.
20 Young N.M., Brisson, J–R., Kelly, J., Watson, D.C., Tessier, L., Lanthier, P.H., Jarrell, H.C., Cadotte, N., St Michael, F., Aberg,
E & Szymanski, C.M (2002) Structure of the N-linked glycan present on multiple glycoproteins in the Gram-negative bacterium, Campylobacter jejuni J Biol Chem 277, 42530–42539.
21 Tsvetkov, Y.E., Shashkov, A.S., Knirel, Y.A & Za¨hringer, U (2001) Synthesis and identification in bacterial lipopolysaccharides
of 5,7-diacetamido-3,5,7,9-tetradeoxy- D -glycero- D -galacto- and - D -glycero- D -talo-non-2-ulosonic acids Carbohydr Res 331, 233–237.
FEBS2003 Polysaccharide structure of F maritimus LPS(Eur J Biochem 270) 1815