| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 TEDA School of Biological Sciences and Biotechnology, Nankai University, 23 Hongda Street, TEDA, Tianjin 300457, P. R. China
2 Tianjin Key Laboratory of Microbial Functional Genomics, Nankai University, 23 Hongda Street, TEDA, Tianjin 300457, P. R. China
3 N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian Federation
4 School of Molecular and Microbial Biosciences (G08), University of Sydney, Sydney, NSW 2006, Australia
Correspondence
Lei Wang
wanglei{at}nankai.edu.cn
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMETHODSRESULTS AND DISCUSSIONREFERENCES |
|---|
These authors contributed equally to this paper.
The GenBank/EMBL/DDBJ accession numbers for the sequences of E. coli O73, O77 and O106 O-antigen gene clusters are DQ000313, DQ000314 and DQ000315, respectively.
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTS AND DISCUSSIONREFERENCES |
|---|
). In Escherichia coli and Salmonella, genes involved in O-antigen synthesis are usually clustered between galF and gnd in the chromosome. These genes encode proteins for the biosynthesis of nucleotide sugars, sugar transferases and proteins for the processing of O antigen, and they include genes encoding flippase (Wzx) and polymerase (Wzy) (Reeves & Wang, 2002). The different O-antigen forms are almost entirely due to genetic variations in their respective O-antigen gene clusters. Sequencing and comparison of various O-antigen gene clusters support the notion that interspecies and intraspecies gene transfers play an important role in the formation of new O-antigen forms (Shepherd et al., 2000; Tarr et al., 2000).
Shigella flexneri, a major cause of bacillary dysentery worldwide, is atypical, as 12 of its 13 serotypes share a common O-antigen backbone. The differences between serotypes are due to glucosyl and/or O-acetyl groups added to sugars in the backbone of the O unit by transferases encoded by genes mapping outside of the common O-antigen gene cluster (Allison & Verma, 2000).
In a study comparing restriction patterns of E. coli O-antigen gene clusters, it has been found that serogroups O17, O44, O73, O77 and O106 have almost identical patterns after MboII digestion of amplified PCR products of O-antigen gene clusters (Coimbra et al., 2000), suggesting that they may also share a common gene cluster. Also, structures of E. coli O17, O44 and O77 (Masoud & Perry, 1996; Staaf et al., 1995; Yildirim et al., 2001) share the same O-repeat backbone (Fig. 1), which is a tetrasaccharide composed of one N-acetyl-D-glucosamine (GlcNAc) and three D-mannose residues. The E. coli O17 and O44 O antigens are modified by a single side-branch glucose residue attached at different positions of the backbone. The Salmonella enterica O : 6,14 (H) O antigen also has the same backbone, with a glucose side chain at another position (di Fabio et al., 1988). The O-antigen gene cluster of S. enterica has been sequenced (Fitzgerald et al., 2003), showing that it encodes genes for the biosynthesis of tetrasaccharide backbone only, and not those for the glucose side-branch.
|
|
METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTS AND DISCUSSIONREFERENCES |
|---|
, which was purchased from the Beijing DingGuo Biotechnology Development Center. The E. coli O17, O44, O73, O77 and O106 type strains K12a, H702c, P12a, E10, H521a (laboratory stock numbers G1298, G1291, G1057, G1075 and G1255, respectively) were obtained from the Institute of Medical and Veterinary Science, Adelaide, Australia. Plasmid pKD20 was kindly provided by Patrick Higgins, Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, USA.
Bacterial cultivation and isolation of LPS.
Bacterial cells were grown to late exponential phase in 8 l Luria–Bertani medium, using a 10 l fermenter (Biostat C-10; B. Braun Biotech International) under constant aeration at 37 °C and pH 7.0. Bacterial cells were washed and dried as described by Robbins & Uchida (1962). LPS of E. coli O73 and the E. coli O44-derived mutant strain H1408 (920 and 1000 mg, respectively) was isolated from dried cells (16.3 and 10.9 g, respectively) by the phenol/water method (Wang et al., 2001a), and purified by precipitation of nucleic acids and proteins with aqueous 50 % TCA, as described previously (Wang & Reeves, 2000).
Isolation of O polysaccharide.
Delipidation of the LPS of E. coli O73 and E. coli O44 mutant strain H1408 (124 and 130 mg, respectively) was performed with aqueous 2 % acetic acid (6 ml) at 100 °C, until lipid A precipitation. The precipitate was removed by centrifugation (13 000 g, 20 min), and the supernatant was fractionated on a column (56x2.6 cm) of Sephadex G-50 (S) (Amersham Biosciences) in 0.05 M pyridinium acetate buffer, pH 4.5, and monitored using a differential refractometer (Knauer). High-molecular-mass polysaccharides were obtained in yields of 48 and 27 % of the LPS weight of E. coli O73 and E. coli O44 mutant strain H1408, respectively.
Chemical analyses.
The polysaccharide of E. coli O73 was hydrolysed with 2 M CF3CO2H (120 °C, 2 h), and sugars were identified by GLC of the alditol acetates, using a Hewlett Packard 5890 chromatograph equipped with an Ultra-2 column (Supelco), and a temperature gradient of 160–290 °C at 3 °C min–1. The absolute configurations of the monosaccharides were determined by GLC of the acetylated (–)-2-octyl glycosides, according to methods described by Gerwig et al. (1979) and Leontein et al. (1978). Methylation of the polysaccharide was performed with CH3I in DMSO, in the presence of sodium methylsulfinylmethanide (Conrad, 1972). Partially methylated monosaccharides were derived by hydrolysis under the same conditions as those in the sugar analysis, and then reduced with NaBH4, acetylated, and analysed by GLC-MS on a Hewlett Packard HP 5989A instrument equipped with a 30 m HP-5ms column (Hewlett Packard), under the same chromatographic conditions as described for GLC.
NMR spectroscopy.
Samples were deuterium-exchanged by freeze-drying twice from D2O, and then examined as solutions in 99.96 % D2O at 27 °C. NMR spectra were recorded on a Bruker DRX-500 spectrometer (Germany) using internal acetone (
H 2.225, C 31.45) as a reference. Two-dimensional NMR spectra were obtained using standard Bruker software, and the Bruker XWINNMR 2.6 program was used to acquire and process the NMR data. Mixing times of 200 and 100 ms were used in total correlation spectroscopy (TOCSY) and rotating Overhauser effect spectroscopy (ROESY) experiments, respectively.
Construction of DNase I shotgun bank.
Chromosomal DNA was prepared as described by Bastin & Reeves (1995). Primers no. 1523 and no. 1524 (Wang et al., 2001b), based on galF and gnd genes, respectively, were used to amplify the DNA of E. coli O73, O77 and O106 O-antigen gene clusters, using the Expand Long Template PCR system (Roche). The PCR cycles used were as follows: denaturation at 94 °C for 10 s, annealing at 60 °C for 30 s, and extension at 68 °C for 15 min. The PCR products were digested with DNase I, and the resulting DNA fragments were cloned into pGEM-T Easy to produce a bank, using the method described previously (Wang & Reeves, 1998).
Sequencing and analysis.
Sequencing was carried out by the Tianjin Biochip Corporation, using an ABI 3730 automated DNA sequencer (Applied Biosystems). Sequence data were assembled using the Staden Package (Staden, 1996). Artemis (Rutherford et al., 2000) was used to identify ORFs, and for annotation. BlockMaker was used to search for conserved motifs. BLAST and PSI-BLAST (Altschul et al., 1997) were used for searching databases, including GenBank, COG and Pfam protein motif databases (Bateman et al., 2002; Tatusov et al., 2001). The SOSUI system (Hirokawa et al., 1998) was used to identify potential transmembrane segments. Sequence alignment and comparisons were performed using the program CLUSTALW (www.ebi.ac.uk/clustalw). The synonymous substitution rate (Ks) and non-synonymous rate (Ka) were calculated using K-Estimator 6.0 (Comeron, 1999).
Deletion and complementation of the E. coli O77 wzy gene and the E. coli O44 wbbG gene.
The Red recombination system of 
phage was used to replace the wzy gene in E. coli O77 and the wbbG gene in E. coli O44; in both cases the gene was replaced by the cat gene, using the methods described by Datsenko & Wanner (2000). The cat gene was PCR amplified from plasmid pKK232-8 using primers binding to the 5' and 3' ends of the cat gene, with each primer carrying 40 bp based on the E. coli O77 DNA that flanks wzy (wl_4696/wl_4697, 5'-ATGCATAAGCAATATTATTCATTATTGTGCAATAAAATGGAGAAAAAAATCACTGG-3'/5'-CTTACTGACCATGATAAATTTTATTTTTAACAAGTAATGCCTTAAAAAAATTACGC-3'), or the E. coli O44 DNA that flanks wbbG (wl_5183/wl_5184, 5'-TAAGCAGCGTCCAAAGTATGTACTTAAGGGTAAAAAATGATTCAGGAGCTAAGGAAGCTAAA-3'/5'-AAAGTGAATCTATTCCATTTTTCCAAATAAGAACTTTTTTTTACGCCCCGCCCTGCCACTCA-3'). The PCR products were transformed, respectively, into E. coli O77 and E. coli O44 type strains carrying pKD20, and chloramphenicol-resistant transformants were selected after induction of the Red genes. The replacements were confirmed by PCR using one primer specific to the cat gene, and the other specific to the DNA flanking the E. coli O77 wzy gene, or the DNA flanking the E. coli O44 wbbG gene. Cloning of the wzy and wbbG genes was performed by PCR amplification from the E. coli O77 and E. coli O44 type strains, respectively, using primer pairs wl_4698/wl_4699 (5'-ATTACCATGGATAAGCAATATTATTCATTATTG-3'/5'-CTGGGATCCAAATAAACCACTTACTGACC-3') binding to the ends of wzy, and wl_5185/wl_5186 (5'-ACGCCATGGATGAGCAAGAAGCTTGAGCTTT-3'/5'-CTGGGATCCCTAAAGTGAATCTATTCCATTT-3') binding to the ends of wbbG. The PCR products were cloned into pTRC99A to make plasmid pLW1062 containing the wzy gene of E. coli O77, and plasmid pLW1180 containing the wbbG gene of E. coli O44. Membrane preparation, SDS-PAGE, and silver staining for visualization of the LPS of the various constructs, were carried out as described by Wang & Reeves (1994).
|
RESULTS AND DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTS AND DISCUSSIONREFERENCES |
|---|
; Staaf et al., 1995; Yildirim et al., 2001). The structure of the E. coli O73 O antigen was determined using O73 polysaccharide obtained by mild acid degradation of LPS isolated from dried cells by the phenol/water procedure (Wang et al., 2001a). Sugar analysis after full acid hydrolysis of the polysaccharide revealed glucose, mannose and glucosamine in the ratio 1.2 : 1 : 0.1. GLC of the acetylated glycosides with (–)-2-octanol showed that all sugars had the D configuration.
The 13C NMR spectrum of the polysaccharide (Fig. 2a) contained major signals for six monosaccharide residues, including those for six anomeric carbons at 98.3–102.9, one nitrogen-bearing carbon (C-2 of GlcN) at 54.4, and one N-acetyl group at 23.3 (CH3) and 174.8 (CO). Accordingly, the 1H NMR spectrum of the polysaccharide contained, inter alia, signals for six anomeric protons at 4.81–5.35, and one N-acetyl group at 2.03. The spectrum also contained minor signals, indicating one or more monosaccharides in non-stoichiometric amounts.
|
). Based on the coupling constant values estimated from the 2D spectra, the spin systems were assigned to three mannose residues (ManI–ManIII), two glucose residues (GlcI and GlcII), and one GlcNAc residue, all of which were in the pyranose form. The integral intensities of the signals for GlcI and GlcII were lower than those of the other sugar residues, and it was concluded that they were present in non-stoichiometric quantities (
80 % of each residue; also, see methylation analysis data below).
|
3 Hz indicated that GlcNAc and both Glc residues were linked. The NMR chemical shifts for H-5 and C-5, compared with published data (Jansson et al., 1989), showed that ManI and ManII were also linked, whereas ManIII was β linked. Significant down-field displacements, due to -glycosylation effects (Lipkind et al., 1988), of the signals for C-6 of ManI, C-2 and C-4 of ManII, C-2 and C-4 of ManIII, and C-3 of -GlcNAc, demonstrated the glycosylation pattern in the O unit. The sequence of the sugar residues in the O unit was determined by a 2D ROESY experiment, which revealed strong inter-residue cross-peaks between the following anomeric protons and protons at the linkage carbons: ManI H-1/ManII H-2, ManII H-1/ManIII H-2, ManIII H-1/GlcNAc H-3, GlcNAc H-1/ManI H-6a, GlcI H-1/ManII H-4, and GlcII H-1/ManIII H-3. This pattern was independently confirmed by a 1H,13C heteronuclear multiple band correlation experiment.
Methylation analysis identified derivatives from terminal glucose, and 2,3-disubstituted, 2,4-disubstituted, 2-substituted and 6-substituted mannose, in the ratio 1.5 : 1 : 1 : 0.3 : 0.5, and a derivative from 3-substituted GlcNAc. A lower than stoichiometric content of the derivative from terminal glucose, and the occurrence of the derivative from 2-substituted mannose, confirmed incomplete substitution of the main chain with the side-branch glucose residues. A lower than expected content of a derivative from 6-substituted mannose could be accounted for by incomplete cleavage of the glycosidic linkage in the GlcNAc
Man disaccharide fragment.
Therefore, the O polysaccharide of E. coli O73 has a branched hexasaccharide repeating unit, with the structure shown in Fig. 1
. The structure includes the O77 tetrasaccharide backbone and two side-branch glucose residues.
Based on the structural data, we conclude that E. coli O17, O44, O73 and O77, and S. enterica O : 6,14 (H), share the O77 O-antigen backbone structure. Therefore, we refer to this group as the O77 group, which also includes E. coli O106 (see below).
The O-antigen gene clusters of the O77 group
The DNA sequences of the O-antigen gene clusters from E. coli O73, O77 and O106 type strains are almost identical (>99 % DNA identity), and they encode six genes transcribed from galF to gnd (Fig. 3). The sequence of the E. coli O44 O-antigen gene cluster, obtained from the genome sequence of E. coli strain 042 (www.sanger.ac.uk/Projects/Escherichia_Shigella/), also shares >99 % DNA identity with each of the O73, O77 and O106 sequences. The E. coli O17 gene cluster was not sequenced, but adjacent-gene PCR was carried out on the type strain using primers based on the genes (including galF and gnd) of E. coli O77. The PCR products produced by each primer pair had the same size in both E. coli O17 and O77 strains (data not shown), indicating that E. coli O17 has the same O-antigen gene cluster as the others. We also found that the O-antigen gene cluster of S. enterica O : 6,14 (H) (GenBank accession no. AY334017) has the same genes in the same order as that of E. coli O77 (Fitzgerald et al., 2003) (Fig. 3). Details of each gene in E. coli O77 O-antigen gene cluster are given below.
|
). S. enterica C1 O unit has two adjacent D-Man-(12)-D-Man linkages, as does the E. coli O77 O unit, and both have one fewer transferase gene than linkages. Therefore, orf1 is proposed to encode a mannosyltransferase for both of the D-Man-(12)-D-Man linkages, and is named wbaC. Orf2 shares 52 % identity with a putative glycosyltransferase involved in E. coli O6 O-antigen assembly. Since the D-Man-β(13)-D-GlcNAc linkage is the only linkage present in both E. coli O77 and O6 O antigens, orf2 is proposed to encode the transferase for the D-Man-β(13)-D-GlcNAc linkage, and given the name wbaD. Orf3 and Orf4 were identified as ManC (mannose-1-phosphate guanylyltransferase) and ManB (phosphomannomutase), respectively, which are involved in the synthesis of GDP-mannose, based on their high level identity to many known ManC and ManB proteins (identity between 60 and 83 %). Therefore, orf3 and orf4 were named manC and manB, respectively.
Orf5 has 12 predicted transmembrane segments, with a large periplasmic loop of 61 aa residues which is a characteristic topology for O-antigen polymerases (Daniels et al., 1998). A mutant strain, H1236, in which orf5 was replaced by a cat gene, produced LPS that consisted of lipid A-core, and lipid A-core with one O unit only, while the E. coli O77 wild-type strain, and H1236 carrying plasmid pLW1062, which contains orf5, both produced the normal LPS (Fig. 4a). Therefore, orf5 was designated wzy, which is the O-antigen polymerase gene. Orf6 has 12 predicted transmembrane segments, with no large loops; this is a feature of Wzx proteins (Liu et al., 1996). Orf6 also shares 43 % similarity to the Wzx protein of Yersinia enterocolitica O : 8, and it was designated wzx, which is the O-antigen flippase gene.
|
). GlcNAc is usually the first residue in E. coli O units, and is transferred by the product of the wecA gene located outside of the O-antigen gene cluster (Alexander & Valvano, 1994).
Location of the genes responsible for the side-branch glucosyl residues in E. coli O44
In Shi. flexneri, the addition of glucosyl residues to the O antigen is due to temperate bacteriophages that contain three genes: gtrA, gtrB and a serotype-specific glucosyltransferase gene (Allison & Verma, 2000). GtrB is thought to be a bactoprenol glucosyltransferase that catalyses the transfer of glucose from UDP-glucose to bactoprenol phosphate (UndP) to give UndP-glucose, and GtrA is thought to be a flippase that translocates UndP-glucose to face the periplasmic space. Both GtrA and GtrB are highly conserved. The protein encoded by the third gene, which catalyses the linkage of a glucosyl group to the O-antigen backbone, is serotype specific (Allison & Verma, 2000).
For O44, we found a set of three genes in the E. coli strain 042 genome that fit the pattern of the Shi. flexneri genes. These genes are located in a prophage adjacent to attL, between ybhB and ybhC (Fig. 5), the normal insertion site of phage (Campbell, 2003). The products of the first two genes share 96 and 86 % identity to GtrA and GtrB, respectively, of E. coli K-12, as well as high-level identity (from 60 to 93 %) to GtrA and GtrB proteins of Shi. flexneri and S. enterica. The products are therefore proposed to be GtrA and GtrB.
|
(14) linkage between the added glucosyl group and GlcNAc. The product was also predicted to have 11 transmembrane segments, with a hydrophilic carboxy-terminal region of 110 aa; this is the typical topological character of GtrI. We replaced this gene with the cat gene to make strain H1408. When compared with its parent on an SDS-PAGE gel, the bands of the ladder representing LPS with different numbers of O units of strain H1408 were closer together, as expected for a smaller O unit. H1408 was transcomplemented to restore the LPS phenotype of the wild-type by plasmid pLW1180 containing the third gene, and the spacing returned to that of the O44 strain (Fig. 4b). The O polysaccharide was obtained from strain H1408, and studied by 1D 1H and 13C spectroscopy, as described above for the E. coli O73 O polysaccharide (Fig. 2b). The 1H and 13C spectra of the mutant polysaccharide were identical to those reported earlier for the E. coli O77 O polysaccharide (Yildirim et al., 2001), showing that the E. coli O44 mutant strain H1408 possesses the same O antigen as that of E. coli O77, with no side-branch glucose substituents. Both LPS size distribution and structural data indicated that the third gene is required for the attachment of the glucose residue to position 4 of the β-D-mannose residue of the O-antigen backbone. It is clear that these three genes constitute a typical set of genes for the addition of a side-branch glucose, and the third gene was named wbbG. Although we have data for O44 only, it is most likely that the proteins for the formation of side-branch glucose residues in O17 and O73 are encoded by similar sets of genes.
The importance of the O77 group O antigens
It has been reported that the O antigen plays an important role in the virulence of Shi. flexneri (Morona et al., 2003; Van den Bosch & Morona, 2003), and O-antigen modification may also be an important factor in enhancing survival and pathogenicity (Allison & Verma, 2000; West et al., 2005). The situation for the O antigens of the O77 group is similar to that in Shi. flexneri, and the same may well apply to this much less-studied group of serovars. It is noteworthy that E. coli O17 and O73 antigens have been found in enterohaemorrhagic E. coli (Bielaszewska et al., 2004), and O44 and O77 antigens have been found in enteroadhesive E. coli (Nataro & Kaper, 1998), and in both cases adaptation to virulence may be important.
It has been proposed that E. coli and S. enterica diverged from a common ancestor about 140 million years ago (Ochman & Wilson, 1987a, b), and proteins encoded by housekeeping genes in the two species share 93 % identity on average, ranging from 76.3 to 100 % (Sharp, 1991). The sequence differences between E. coli O77 and S. enterica O:6,14 (H) are consistent with the O77-group gene cluster having been in the common ancestor, and diverged as the species diverged, rather than having been independently acquired, or acquired by one species from the other. The apparent long history of this O antigen in E. coli and S. enterica is not typical, as most O antigens in each species are not found in the other. The survival of the O antigen indicates that it is highly adaptive in E. coli and S. enterica, with their rather different niches.
|
ACKNOWLEDGEMENTS |
|---|
Edited by: D. L. Gally
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTS AND DISCUSSIONREFERENCES |
|---|
Allison, G. E. & Verma, N. K. (2000). Serotype-converting bacteriophages and O-antigen modification in Shigella flexneri. Trends Microbiol 8, 17–23.[CrossRef][Medline]
Altschul, S. F., Madden, T. L., Schaffer, A. A., Zhang, J., Zhang, Z., Miller, W. & Lipman, D. J. (1997). Gapped BLAST and PSI-BLAST: a new generation of protein database search programs. Nucleic Acids Res 25, 3389–3402.
Bastin, D. A. & Reeves, P. R. (1995). Sequence and analysis of the O antigen gene (rfb) cluster of Escherichia coli O111. Gene 164, 17–23.[CrossRef][Medline]
Bateman, A., Birney, E., Cerruti, L., Durbin, R., Etwiller, L., Eddy, S. R., Griffiths-Jones, S., Howe, K. L., Marshall, M. & Sonnhammer, E. L. (2002). The Pfam protein families database. Nucleic Acids Res 30, 276–280.
Bielaszewska, M., Fell, M., Greune, L., Prager, R., Fruth, A., Tschape, H., Schmidt, M. A. & Karch, H. (2004). Characterization of cytolethal distending toxin genes and expression in shiga toxin-producing Escherichia coli strains of non-O157 serogroups. Infect Immun 72, 1812–1816.
Campbell, A. (2003). Prophage insertion sites. Res Microbiol 154, 277–282.[Medline]
Coimbra, R. S., Grimont, F., Lenormand, P., Burguiere, P., Beutin, L. & Grimont, P. A. (2000). Identification of Escherichia coli O-serogroups by restriction of the amplified O-antigen gene cluster (rfb-RFLP). Res Microbiol 151, 639–654.[Medline]
Comeron, J. M. (1999). K-Estimator: calculation of the number of nucleotide substitutions per site and the confidence intervals. Bioinformatics 15, 763–764.
Conrad, H. E. (1972). Methylation of carbohydrates with methyl iodide in dimethyl sulfoxide in the presence of methylsulfinylanion. Methods Carbohydr Chem 6, 361–364.
Daniels, C., Vindurampulle, C. & Morona, R. (1998). Overexpression and topology of the Shigella flexneri O-antigen polymerase (Rfc/Wzy). Mol Microbiol 28, 1211–1222.[CrossRef][Medline]
Datsenko, K. A. & Wanner, B. L. (2000). One-step inactivation of chromosomal genes in Escherichia coli K-12 using PCR products. Proc Natl Acad Sci U S A 97, 6640–6645.
di Fabio, J. L., Brisson, J. R. & Perry, M. B. (1988). Structure of the major lipopolysaccharide antigenic O-chain produced by Salmonella carrau (O : 6, 14, 24). Carbohydr Res 179, 233–244.[CrossRef][Medline]
Fitzgerald, C., Sherwood, R., Gheesling, L. L., Brenner, F. W. & Fields, P. I. (2003). Molecular analysis of the rfb O antigen gene cluster of Salmonella enterica serogroup O : 6,14 and development of a serogroup-specific PCR assay. Appl Environ Microbiol 69, 6099–6105.
Gerwig, G. J., Kamerling, J. P. & Vliegenthart, J. F. G. (1979). Determination of the absolute configuration of monosaccharides in complex carbohydrates by capillary GLC. Carbohydr Res 77, 1–7.[CrossRef]
Hirokawa, T., Boon-Chieng, S. & Mitaku, S. (1998). SOSUI: Classification and secondary structure prediction system for membrane proteins. Bioinformatics 14, 378–379.
Jansson, P. E., Kenne, L. & Widmalm, G. (1989). Computer-assisted structural analysis of polysaccharides with an extended version of CASPER using 1H- and 13C-n.m.r. data. Carbohydr Res 188, 169–191.[CrossRef][Medline]
Lee, S. J., Romana, L. K. & Reeves, P. R. (1992). Sequence and structural analysis of the rfb (O antigen) gene cluster from a group C1 Salmonella enterica strain. J Gen Microbiol 138, 1843–1855.
Leontein, K., Lindberg, B. & Lonngren, J. (1978). Assignment of absolute configuration of sugars by GLC of their acetylated glycosides formed from chiral alcohols. Carbohydr Res 62, 359–362.[CrossRef]
Lipkind, G. M., Shashkov, A. S., Knirel, Y. A., Vinogradov, E. V. & Kochetkov, N. K. (1988). A computer-assisted structural analysis of regular polysaccharides on the basis of 13C-n.m.r. data. Carbohydr Res 175, 59–75.[CrossRef][Medline]
Liu, D., Cole, R. & Reeves, P. R. (1996). An O-antigen processing function for Wzx(RfbX): a promising candidate for O-unit flippase. J Bacteriol 178, 2102–2107.
Masoud, H. & Perry, M. B. (1996). Structural characterization of the O-antigenic polysaccharide of Escherichia coli serotype O17 lipopolysaccharide. Biochem Cell Biol 74, 241–248.[Medline]
Morona, R., Daniels, C. & Van Den Bosch, L. (2003). Genetic modulation of Shigella flexneri 2a lipopolysaccharide O antigen modal chain length reveals that it has been optimized for virulence. Microbiology 149, 925–939.
Nataro, J. P. & Kaper, J. B. (1998). Diarrheagenic Escherichia coli. Clin Microbiol Rev 11, 142–201.
Ochman, H. & Wilson, A. C. (1987a). Evolution in bacteria: evidence for a universal substitution rate in cellular genomes. J Mol Evol 26, 74–86.[CrossRef][Medline]
Ochman, H. & Wilson, A. C. (1987b). Evolutionary history of enteric bacteria. In Escherichia coli and Salmonella typhimurium: Cellular and Molecular Biology, pp. 1649–1654. Edited by F. C. Neidhardt and others. Washington, DC: American Society for Microbiology.
Reeves, P. P. & Wang, L. (2002). Genomic organization of LPS-specific loci. Curr Top Microbiol Immunol 264, 109–135.[Medline]
Robbins, P. W. & Uchida, T. (1962). Studies on the chemical basis of the phage conversion of O-antigens in the E-group Salmonella. Biochemistry 1, 323–335.[CrossRef][Medline]
Rutherford, K., Parkhill, J., Crook, J., Horsnell, T., Rice, P., Rajandream, M. A. & Barrell, B. (2000). Artemis: sequence visualisation and annotation. Bioinformatics 16, 944–945.
Sharp, P. M. (1991). Determinants of DNA sequence divergence between Escherichia coli and Salmonella typhimurium: codon usage, map position, and concerted evolution. J Mol Evol 33, 23–33.[CrossRef][Medline]
Shepherd, J. G., Wang, L. & Reeves, P. R. (2000). Comparison of O-antigen gene clusters of Escherichia coli (Shigella) sonnei and Plesiomonas shigelloides O17: sonnei gained its current plasmid-borne O-antigen genes from P. shigelloides in a recent event. Infect Immun 68, 6056–6061.
Staaf, M., Widmalm, G., Weintraub, A. & Nataro, J. P. (1995). Structural elucidation of the O-antigenic polysaccharide from Escherichia coli O44 : H18. Eur J Biochem 233, 473–477.[Medline]
Staden, R. (1996). The Staden sequence analysis package. Mol Biotechnol 5, 233–241.[Medline]
Tarr, P. I., Schoening, L. M., Yea, Y. L., Ward, T. R., Jelacic, S. & Whittam, T. S. (2000). Acquisition of the rfb-gnd cluster in evolution of Escherichia coli O55 and O157. J Bacteriol 182, 6183–6191.
Tatusov, R. L., Natale, D. A., Garkavtsev, I. V., Tatusova, T. A., Shankavaram, U. T., Rao, B. S., Kiryutin, B., Galperin, M. Y., Fedorova, N. D. & Koonin, E. V. (2001). The COG database: new developments in phylogenetic classification of proteins from complete genomes. Nucleic Acids Res 29, 22–28.
Van den Bosch, L. & Morona, R. (2003). The actin-based motility defect of a Shigella flexneri rmlD rough LPS mutant is not due to loss of IcsA polarity. Microb Pathog 35, 11–18.[CrossRef][Medline]
Wang, L. & Reeves, P. R. (1994). Involvement of the galactosyl-1-phosphate transferase encoded by the Salmonella enterica rfbP gene in O antigen subunit processing. J Bacteriol 176, 4348–4356.
Wang, L. & Reeves, P. R. (1998). Organization of Escherichia coli O157 O antigen gene cluster and identification of its specific genes. Infect Immun 66, 3545–3551.
Wang, L. & Reeves, P. R. (2000). The Escherichia coli O111 and Salmonella enterica O35 gene clusters: gene clusters encoding the same colitose-containing O antigen are highly conserved. J Bacteriol 182, 5256–5261.
Wang, L., Briggs, C. E., Rothemund, D., Fratamico, P., Luchansky, J. B. & Reeves, P. R. (2001a). Sequence of the E. coli O104 antigen gene cluster and identification of O104-specific genes. Gene 270, 231–236.[CrossRef][Medline]
Wang, L., Qu, W. & Reeves, P. R. (2001b). Sequence analysis of four Shigella boydii O-antigen loci: implication for Escherichia coli and Shigella relationships. Infect Immun 69, 6923–6930.
West, N. P., Sansonetti, P., Mounier, J., Exley, R. M., Parsot, C., Guadagnini, S., Prevost, M. C., Prochnicka-Chalufour, A., Delepierre, M. & other authors (2005). Optimization of virulence functions through glucosylation of Shigella LPS. Science 307, 1313–1317.
Yildirim, H., Weintraub, A. & Widmalm, G. (2001). Structural studies of the O-polysaccharide from the Escherichia coli O77 lipopolysaccharide. Carbohydr Res 333, 179–183.[CrossRef][Medline]
Received 7 November 2006;
revised 27 March 2007;
accepted 3 April 2007.
This article has been cited by other articles:
|
|
 |
|
  C. G. Clark, A. M. Kropinski, H. Parolis, C. C. R. Grant, K. M. Trout-Yakel, K. Franklin, L.-K. Ng, N. A. Paramonov, L. A. S. Parolis, K. Rahn, et al. Escherichia coli O123 O antigen genes and polysaccharide structure are conserved in some Salmonella enterica serogroups J. Med. Microbiol., July 1, 2009; 58(7): 884 - 894. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. Mullane, P. O'Gaora, J. E. Nally, C. Iversen, P. Whyte, P. G. Wall, and S. Fanning Molecular Analysis of the Enterobacter sakazakii O-Antigen Gene Locus Appl. Envir. Microbiol., June 15, 2008; 74(12): 3783 - 3794. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Stevenson, M. Dieckelmann, and P. R. Reeves Determination of Glycosyltransferase Specificities for the Escherichia coli O111 O Antigen by a Generic Approach Appl. Envir. Microbiol., February 15, 2008; 74(4): 1294 - 1298. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| INT J SYST EVOL MICROBIOL | MICROBIOLOGY | J GEN VIROL |
| J MED MICROBIOL | ALL SGM JOURNALS | |
