Localizing seizure-onset zones in presurgical evaluation of drug-resistant epilepsy by electroencephalography/fMRI: effectiveness of alternative thresholding strategies

BACKGROUND AND PURPOSE

Simultaneous EEG/fMRI is an effective noninvasive tool for identifying and localizing the SOZ in patients with focal epilepsy. In this study, we evaluated different thresholding strategies in EEG/fMRI for the assessment of hemodynamic responses to IEDs in the SOZ of drug-resistant epilepsy.

MATERIALS AND METHODS

Sixteen patients with focal epilepsy were examined by using simultaneous 92-channel EEG and BOLD fMRI. The temporal fluctuation of epileptiform signals on the EEG was extracted by independent component analysis to predict the hemodynamic responses to the IEDs. We applied 3 different threshold criteria to detect hemodynamic responses within the SOZ: 1) PA, 2) a fixed threshold at P < .05 corrected for multiple comparison (FWE), and 3) FAV (4000 ± 200 activated voxels within the brain).

RESULTS

PA identified the SOZ in 9 of 16 patients; FWE resulted in concordant BOLD signal correlates in 11 of 16, and FAV in 13 of 16 patients. Hemodynamic responses were detected within the resected areas in 5 (PA), 6 (FWE), and 8 (FAV) of 10 patients who remained seizure-free after surgery.

CONCLUSIONS

EEG/fMRI is a noninvasive tool for the presurgical work-up of patients with epilepsy, which can be performed during seizure-free periods and is complementary to the ictal electroclinical assessment. Our findings suggest that the effectiveness of EEG/fMRI in delineating the SOZ may be further improved by the additional use of alternative analysis strategies such as FAV.

Thought disorder: a left lateralised breakdown of the language network

Introduction

Structural and functional deviations in schizophrenic patients with formal thought disorder (FTD) point towards a dysfunction within left sided language network.

Objectives

Independent component analysis (ICA), a new approach to fMRI analysis, enables to target the question of a network dysfunction directly. Using this method in healthy controls it was possible to identify the language networks separately for the left and the right hemispheres In the present study we use ICA analysis to examine changes of the language network separate for each hemisphere in relation to the severity of FTD.

Aims

We hypothesize increasing disintegration with increasing severity of FTD only in the left sided language network while the right language network should remain unaffected.

Methods

We investigated 16 schizophrenic patients with different severity of FTD and matched healthy controls using ICA decomposition of the BOLD signal. The spatial similarity of the individual language networks was correlated to the severity of FTD.

Results

The integrity of the left language network decrease with increasing severity of FTD (r = -0.79, p < 0.01), while the integrity of the right language network show no significant correlation to the severity of FTD.

Conclusion

For the first time the isolated breakdown of the left sided language network was linked specifically to schizophrenic FTD. This result unites older manly left hemispheric findings of structural and functional abnormalities in schizophrenic FTD.

BOLD correlates of EEG alpha phase-locking and the fMRI default mode network

Phase locking or synchronization of brain areas is a key concept of information processing in the brain. Synchronous oscillations have been observed and investigated extensively in EEG during the past decades. EEG oscillations occur over a wide frequency range. In EEG, a prominent type of oscillations is alpha-band activity, present typically when a subject is awake, but at rest with closed eyes. The spectral power of alpha rhythms has recently been investigated in simultaneous EEG/fMRI recordings, establishing a wide-range cortico-thalamic network. However, spectral power and synchronization are different measures and little is known about the correlations between BOLD effects and EEG synchronization. Interestingly, the fMRI BOLD signal also displays synchronous oscillations across different brain regions. These oscillations delineate so-called resting state networks (RSNs) that resemble the correlation patterns of simultaneous EEG/fMRI recordings. However, the nature of these BOLD oscillations and their relations to EEG activity is still poorly understood. One hypothesis is that the subunits constituting a specific RSN may be coordinated by different EEG rhythms. In this study we report on evidence for this hypothesis. The BOLD correlates of global EEG synchronization (GFS) in the alpha frequency band are located in brain areas involved in specific RSNs, e.g. the 'default mode network'. Furthermore, our results confirm the hypothesis that specific RSNs are organized by long-range synchronization at least in the alpha frequency band. Finally, we could localize specific areas where the GFS BOLD correlates and the associated RSN overlap. Thus, we claim that not only the spectral dynamics of EEG are important, but also their spatio-temporal organization.

N-Acetylated domains in heparan sulfates revealed by a monoclonal antibody against the Escherichia coli K5 capsular polysaccharide. Distribution of the cognate epitope in normal human kidney and transplant kidney with chronic vascular rejection

The Escherichia coli K5 capsular polysaccharide has the same (GlcUA-->GlcNAc)n structure as the nonsulfated heparan sulfate/heparin precursor polysaccharide. A monoclonal antibody (mAb 865) against the K5 polysaccharide has been described (Peters, H., Jürs, M., Jann, B., Jann, K., Timmis, K. N., and Bitter-Sauermann, D. (1985) Infect. Immun. 50, 459-466). In this report, we demonstrate the binding of anti-K5 mAb 865 to N-acetylated sequences in heparan sulfates and heparan sulfate proteoglycans but not to heparin. This is shown by direct binding and fluid phase inhibition of mAb 865 in an enzyme-linked immunosorbent assay. In this system we found that the binding of the mAb decreased with increasing sulfate content of the polysaccharide. By testing chemically modified K5 and heparin polysaccharides, we found that each of the modifications that occur during heparan sulfate (HS) synthesis (N-sulfation, C-5 epimerization, and O-sulfation) prevents recognition by mAb 865. Samples of heparan sulfate from human aorta (HS-II) were selectively degraded so as to allow the separate isolation of N-sulfated and N-acetylated block structures. N-Sulfated oligosaccharides (obtained after N-deacetylation by hydrazinolysis followed by nitrous acid deamination at pH 3.9) were not recognized by mAb 865, in contrast to N-acetylated oligosaccharides (obtained after nitrous acid deamination at pH 1.5), although the reactivity was lower than for intact HS-II. Analysis of the latter's pH 1.5 deamination products by gel filtration indicated that a minimal size of 18 saccharide units was necessary for antibody binding. These results lead us to propose bivalent antibody-heparan sulfate interaction, in which both F(ab) domains of the mAb interact with their epitopes, both of which are present in a single large (>/=18 saccharide units) N-acetylated domain and additionally with single epitopes present in two N-acetylated sequences (each <18 saccharide units) bridged by a short N-sulfated domain. Immunohistochemistry with mAb 865 on cryostat sections of normal human kidney tissue, revealed its binding to most but not all renal basement membranes. However, all renal basement membranes contain heparan sulfate, as shown by a mAb against heparitinase-digested heparan sulfate stubs (mAb 3G10). This finding indicates that not all heparan sulfate chains present in basement membranes express the mAb 865 epitopes. Besides the normal distribution, mAb 865 staining was found in fibrotic and sclerotic lesions in vessels, interstitium, and mesangium in transplant kidneys with chronic vascular rejection. Occasionally, a decrease of staining was observed within tubulo-interstitium and glomeruli. These findings show that N-acetylated sequences in heparan sulfates can be demonstrated by anti-K5 mAb 865 in normal and diseased kidneys.

The three-dimensional structure of capsule-specific CMP: 2-keto-3-deoxy-manno-octonic acid synthetase from Escherichia coli

CMP-Kdo synthetases from Gram-negative bacteria activate Kdo for incorporation into lipo- and capsule-polysaccharides. Here we report the crystal structure of the capsule-specific synthetase from E. coli at 2.3 A resolution. The enzyme is a dimer of 2 x 245 amino acid residues assuming C2 symmetry. It contains a central predominantly parallel beta-sheet with surrounding helices. The chain fold is novel; it is remotely related to a double Rossmann fold. A large pocket at the carboxyl terminal ends of the central. beta-strands most likely accommodates the catalytic center. A putative phosphate binding site at the loop between the first beta-strand and the following helix is indicated by a bound iridium hexachloride anion.

Analysis of the enzymatic cleavage (beta elimination) of the capsular K5 polysaccharide of Escherichia coli by the K5-specific coliphage: reexamination

The capsular K5 polysaccharide of Escherichia coli is the receptor of the capsule-specific coliphage K5, which harbors an enzyme that degrades the capsular K5 polysaccharide to a number of oligosaccharides. Analysis of the degradation products using gel permeation chromatography, the periodate-thiobarbituric acid and bicinchoninic acid reactions, and nuclear magnetic resonance spectroscopy showed that the major reaction products are hexa-, octa-, and decasaccharides with 4,5-unsaturated glucuronic acid (delta4,5GlcA) at their nonreducing end. Thus, the bacteriophage enzyme is a K5 polysaccharide lyase and not, as we had reported previously, an endo-N-acetylglucosaminidase.

A novel cell surface polysaccharide in Pseudomonas putida WCS358, which shares characteristics with Escherichia coli K antigens, is not involved in root colonization

Previously we have shown that flagella and the O-specific polysaccharide of lipopolysaccharide play a role in colonization of the potato root by plant growth-promoting Pseudomonas strains WCS374 and WCS358. In this paper, we describe a novel cell surface-exposed structure in Pseudomonas putida WCS358 examined with a specific monoclonal antibody. This cell surface structure appeared to be a polysaccharide, which was accessible to the monoclonal antibody at the outer cell surface. Further study revealed that it does not contain 2-keto-3-deoxyoctonate, heptose, or lipid A, indicating that it is not a second type of lipopolysaccharide. Instead, the polysaccharide shared some characteristics with K antigen described for Escherichia coli. From a series of 49 different soil bacteria tested, only one other potato plant growth-promoting Pseudomonas strain reacted positively with the monoclonal antibody. Mutant cells lacking the novel antigen were efficiently isolated by an enrichment method involving magnetic antibodies. Mutant strains defective in the novel antigen contained normal lipopolysaccharide. One of these mutants was affected in neither its ability to adhere to sterile potato root pieces nor its ability to colonize potato roots. We conclude that the bacterial cell surface of P. putida WCS358 contains at least two different polysaccharide structures. These are the O-specific polysaccharide of lipopolysaccharide, which is relevant for potato root colonization, and the novel polysaccharide, which is not involved in adhesion to or colonization of the potato root.

NMR investigation of the 6-deoxy-L-talose-containing O45, O45-related (O45rel), and O66 polysaccharides of Escherichia coli

The structures of the 6-deoxytalose-containing O-specific polysaccharides from the O45 antigen, an O45-related antigen (O45rel), and the O66 antigen (lipopolysaccharides, LPSs) of Escherichia coli were elucidated by chemical characterization and by one- and two-dimensional 1H and 13C NMR spectroscopy. The O45 and O45-related polysaccharides have the following general structure: [formula: see text] For the O45 antigen, X is alpha-D-FucpNAc and for the O45-related antigen, X is beta-D-GlcpNAc. The structure of the O66 polysaccharide is [formula: see text]

Region 2 of the Escherichia coli K5 capsule gene cluster encoding proteins for the biosynthesis of the K5 polysaccharide

The nucleotide sequence of region 2 of the Escherichia coli K5 capsule gene cluster has been determined. This region, essential for the biosynthesis of the K5 polysaccharide, contained four genes, termed kfiA-D. The G + C ratio was 33.4%, which was lower than the typical G + C ratio for E. coli and that of the flanking regions 1 and 3 in the K5 capsule gene cluster. Three major RNA transcripts were detected within region 2 by Northern blotting and three promoters located by transcript mapping. Promoter activity was confirmed by promoter-probe analysis. The predicted amino acid sequence of KfiC had homology to a number of glycosyl transferase enzymes and overexpression of the KfiC gene resulted in increased K5 transferase activity. The predicted amino acid sequence of KfiD had homology to a number of NAD-dependent dehydrogenase enzymes and was demonstrated to be a UDP-glucose dehydrogenase that catalyses the information of UDP-glucuronic acid from UDP-glucose.

Expression and characterization of UDPGlc dehydrogenase (KfiD), which is encoded in the type-specific region 2 of the Escherichia coli K5 capsule genes

Region 2 of the Escherichia coli K5 capsule gene cluster contains four genes (kfiA through -D) which encode proteins involved in the synthesis of the K5 polysaccharide. A DNA fragment containing kfiD was amplified by PCR and cloned into the gene fusion vector pGEX-2T to generate a GST-KfiD fusion protein. The fusion protein was isolated from the cytoplasms of IPTG (isopropyl-beta-D-thiogalactopyranoside)-induced recombinant bacteria by affinity chromatography and cleaved with thrombin. The N-terminal amino acid sequence of the cleavage product KfiD' corresponded to the predicted amino acid sequence of KfiD with an N-terminal glycyl-seryl extension from the cleavage site of the fusion protein. Anti-KfiD antibodies obtained with KfiD' were used to isolate the intact KfiD protein from the cytoplasms of E. coli organisms overexpressing the kfiD gene. The fusion protein, its cleavage product (KfiD'), and overexpressed KfiD converted UDPGlc to UDPGlcA. The KfiD protein could thus be characterized as a UDPglucose dehydrogenase.

NMR reinvestigation of two N-acetylneuraminic acid-containing O-specific polysaccharides (O56 and O24) of Escherichia coli

Structures for the N-acetylneuraminic acid (Neu5Ac)-containing O56 and O24 polysaccharides of Escherichia coli have been reported previously. During these studies unusual chemical shifts had been observed for the NMR signals for H-3eq and C-3 of the Neu5Ac residues of both polysaccharides. In further pursuing this phenomenon, we have reinvestigated the O56 and O24 polysaccharides as well as derived oligosaccharides by one- and two-dimensional NMR spectroscopy. The results showed that structures of both polysaccharides (PSs) had to be modified and formulated as [formula: see text] 2D ROESY spectra revealed a strong NOE between H-3eq of Neu5Ac and the protons of the side-chain sugar (H-3 and H-5 of alpha-D-Gal p in the O56 PS and H-3 of alpha-D-Glc p in the O24 PS) and also between H-3ax of Neu5Ac and H-3 of beta-D-Glc p in the main chain. This indicated a close spatial association of the seven-linked alpha-Neu5Ac and the side-chain residues alpha-D-Gal p (O56 PS) and alpha-D-Glc p (O25 PS), respectively. The strong long-range spatial contacts caused the unusual chemical shifts of H-3eq and C-3 of Neu5Ac.

Expression of the O9 polysaccharide of Escherichia coli: sequencing of the E. coli O9 rfb gene cluster, characterization of mannosyl transferases, and evidence for an ATP-binding cassette transport system

The rfb gene cluster of Escherichia coli O9 directs the synthesis of the O9-specific polysaccharide which has the structure -->2-alpha-Man-(1-->2)-alpha-Man-(1-->2)-alpha-Man-(1-->3)-alpha- Man-(1-->. The E. coli O9 rfb cluster has been sequenced, and six genes, in addition to the previously described rfbK and rfbM, were identified. They correspond to six open reading frames (ORFs) encoding polypeptides of 261, 431, 708, 815, 381, and 274 amino acids. They are all transcribed in the counter direction to those of the his operon. No gene was found between rfb and his. A higher G+C content indicated that E. coli O9 rfb evolved independently of the rfb clusters from other E. coli strains and from Shigella and Salmonella spp. Deletion mutagenesis, in combination with analysis of the in vitro synthesis of the O9 mannan in membranes isolated from the mutants, showed that three genes (termed mtfA, -B, and -C, encoding polypeptides of 815, 381, and 274 amino acids, respectively) directed alpha-mannosyl transferases. MtfC (from ORF274), the first mannosyl transferase, transfers a mannose to the endogenous acceptor. It critically depended on a functional rfe gene (which directs the synthesis of the endogenous acceptor) and initiates the growth of the polysaccharide chain. MtfB (from ORF381) then transfers two mannoses into the 3 position of the previous mannose, and MtfA (from ORF815) transfers three mannoses into the 2 position. Further chain growth needs only the two transferases MtfA and MtfB. Thus, there are fewer transferases needed than the number of sugars in the repeating unit. Analysis of the predicted amino acid sequence of the ORF261 and ORF431 proteins indicated that they function as components of an ATP-binding cassette transport system. A possible correlation between the mechanism of polymerization and mode of membrane translocation of the products is discussed.

Characterization and localization of the KpsE protein of Escherichia coli K5, which is involved in polysaccharide export

In Escherichia coli with group II capsules, the synthesis and cellular expression of capsular polysaccharide are encoded by the kps gene cluster. This gene cluster is composed of three regions. The central region 2 encodes proteins involved in polysaccharide synthesis, and the flanking regions 1 and 3 direct the translocation of the finished polysaccharide across the cytoplasmic membrane and its surface expression. The kps genes of the K5 polysaccharide, which is a group II capsular polysaccharide, have been cloned and sequenced. Region 1 contains the kpsE, -D, -U, -C, and -S genes. In this communication we describe the KpsE protein, the product of the kpsE gene. A truncated kpsE gene was fused with a truncated beta-galactosidase gene to generate a fusion protein containing the first 375 amino acids of beta-galactosidase and amino acids 67 to 382 of KpsE (KpsE'). This fusion protein was isolated and cleaved with factor Xa, and the purified KpsE' was used to immunize rabbits. Intact KpsE was extracted from the membranes of a KpsE-overexpressing recombinant strain with octyl-beta-glucoside. It was purified by affinity chromatography with immobilized anti-KpsE antibodies. Cytofluorometric analysis using the anti-KpsE antibodies with whole cells and spheroplasts, as well as sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting (immunoblotting) of proteins from spheroplasts and membranes before and after treatment with proteinase K, indicated that the KpsE protein is associated with the cytoplasmic membrane and has an exposed periplasmic domain. By TnphoA mutagenesis and by constructing beta-lactamase fusions to the KpseE protein, it was possible to determine the topology of the KpsE protein within the cytoplasmic membrane.

Isolation from recombinant Escherichia coli and characterization of CMP-Kdo synthetase, involved in the expression of the capsular K5 polysaccharide (K-CKS)

In Escherichia coli with group II capsules, the synthesis of capsular polysaccharide and its cellular expression are encoded by the kps gene cluster, which is composed of three regions. The central region 2 encodes proteins involved in polysaccharide synthesis, and the flanking regions 1 and 3 direct the translocation of the finished polysaccharide across the cytoplasmic membrane and its surface expression. The kps genes of E. coli with the group II capsular K5 polysaccharide, have been cloned and sequenced. Region 1 contains the kpsE, D, U, C and S genes. In this communication we describe the overexpression of the kpsD and kpsU genes as well as the isolation of the KpsU protein from the recombinant bacteria by chloroform treatment. The purified KpsU protein exhibited CMP-Kdo-synthetase activity. The N-terminal sequence and two internal peptide sequences of the isolated protein are in agreement with that previously predicted from the DNA sequence of the kpsU gene. The kinetic data of the CMP-Kdo-synthetase participating in K5 capsule expression (K-CMP-Kdo-synthetase) differ from those described for the CMP-Kdo-synthetase, participating in lipopolysaccharide synthesis (L-CMP-Kdo-synthetase).

Structure of the O16 polysaccharide from Escherichia coli O16:K1: an NMR investigation

The polysaccharide moiety of the O16 antigen (lipopolysaccharide) consists of D-glucopyranose, D-galactofuranose, L-rhamnopyranose, and 2-acetamido-2-deoxy-D-glucopyranose in the molar ratios 1:1:1:1. It is O-acetylated with one acetyl group per repeating unit. One- and two-dimensional NMR spectroscopy of the polysaccharide before and after O-deacetylation showed that the O16 polysaccharide has the structure [formula: see text]

Regulation of Escherichia coli K5 capsular polysaccharide expression: evidence for involvement of RfaH in the expression of group II capsules

Expression of the Escherichia coli K5 antigen was used as a model system to study the role of known regulators of gene expression on production of group II capsules in E. coli. Only mutations in the rfaH gene had an effect on production of the K5 antigen, abolishing the expression of any detectable capsule at 37 degrees C. None of the mutations studied induced capsule expression at 18 degrees C. A sequence, termed JUMPstart, found in group II capsule gene clusters and upstream of a number of polysaccharide biosynthesis genes in enteric bacteria is homologous to sequences found in RfaH regulated operons. This may indicate a common mode of regulation of these polysaccharide biosynthesis genes by RfaH.

Structural comparison of the O6 specific polysaccharides from E. coli O6:K2:H1, E. coli O6:K13:H1, and E. coli O6:K54:H10

Two distinct forms of the O6 antigen (LPS) from E. coli were analysed using 1H and 13C NMR spectroscopy. Their structures were found to be [formula: see text] In the O6-specific polysaccharide from E. coli O6:K2 and O6:K13, X is beta-D-Glc p, as had previously been shown for the O6 polysaccharide from E. coli O6:K15; in the O6 specific polysaccharide from E. coli O6:K54, X is beta-D-Glc pNAc.

Structure of the O83-specific polysaccharide of Escherichia coli O83:K24:H31

The polysaccharide moiety of the O83 antigen (lipopolysaccharide, LPS) consists of D-glucose, D-galactose, 2-acetamido-2-deoxy-D-glucose, and D-glucuronic acid in the molar ratios 1:2:1:1. Methylation analysis of the polysaccharide and derived oligosaccharides as well as one- and two-dimensional 1H and 13C NMR spectroscopy of the polysaccharide at pD 1 and 6 showed that the O83 polysaccharide has the primary structure-->6)-alpha-D-Glc p-(1-->4)-beta-D-Glc pA-(1-->6)-beta-D-Gal p-(1-->4)-beta-D- Gal p-(1-->4)-beta-D-Glc pNAc-(1-->.

Substrate specificities of glycosyltransferases involved in formation of heparin precursor and E. coli K5 capsular polysaccharides

The E. coli K5 capsular polysaccharide is composed of 4)GlcpA(beta 1-4)GlcpNAc(alpha 1-disaccharide units. A partially N-deacetylated/N-sulfated heptasaccharide, derived from this polymer and having a nonreducing terminal GlcNAc unit, was used as acceptor for a mastocytoma microsomal GlcA-transferase involved in heparin biosynthesis. An octasaccharide with nonreducing-terminal GlcA similarly served as acceptor for the microsomal GlcNAc-transferase. Analysis of the labeled octa- and nona-saccharides formed by transfer of monosaccharide units from UDP-[14C]GlcA and UDP-[3H]GlcNAc, respectively, showed that both glycosyltransferases could utilize partially N-sulfated acceptors. The GlcA-transferase showed a marked preference for a terminal GlcNAc-GlcA-GlcNSO3-sequence, particularly when this sequence was followed by an additional N-sulfated disaccharide unit. Enzymes catalyzing the same GlcA and GlcNAc transfer reactions were solubilized from E. coli K5 membranes. The K5 capsular polysaccharide, like the heparin/heparan sulfate precursor polysaccharide, thus probably grows by stepwise, alternating addition of the two constituent monosaccharide units, from the corresponding UDP-sugars, to the nonreducing ends of the chains. Moreover, the bacterial glycosyltransferases utilized the same partially N-sulfated oligosaccharide substrates as the mammalian enzymes, and with similar preference for N-sulfate groups in certain positions.

Structure of the O-specific polysaccharide of the O22-antigen (LPS) from Escherichia coli O22:K13

The polysaccharide moiety of the O22-antigen (lipopolysaccharide, LPS) consists of 2-acetamido-2-deoxy-D-galactose, D-glucuronic acid, D-glucose, and D-galactose in the molar ratios 2:1:1:1. Methylation analysis as well as 1D and 2D NMR spectroscopy showed that the O22 polysaccharide has the primary structure [formula: see text]

Genetic analysis of Escherichia coli O9 rfb: identification and DNA sequence of phosphomannomutase and GDP-mannose pyrophosphorylase genes

Subcloning, transposon insertion, and deletion analysis revealed that the Escherichia coli O9 rfb region is about 12 kb in size. The region encodes at least seven polypeptides of 89, 74, 55, 50, 44, 41 and 39.5 kDa. Southern hybridization analysis of rfb regions of E. coli O8 and O9, and Klebsiella O3 and O5 serotypes (all of these O polysaccharides are mannose homopolymers and the structures of the repeating unit of E. coli O9 and Klebsiella O3 are identical) showed that a central region specific for E. coli O9 and Klebsiella O3 is flanked by two regions common to all four. Complementation experiments using strains with known defects and specific tests for the enzymic activity showed that the 50 and 55 kDa polypeptides, encoded by the common region, are phosphomannomutase (PMM) and GDP-mannose pyrophosphorylase (GMP), respectively. Nucleotide sequencing of the region revealed the presence of two genes, rfbK and rfbM, analogous to the corresponding genes of Salmonella typhimurium. In E. coli O9, rfbK and rfbM encode proteins of 460 amino acids (50,809 Da) and 471 amino acids (52,789 Da). The amino acid sequence of GMP was conserved in RfbMs of E. coli O7 and Salmonella groups B, C1 and C2, CpsB of S. typhimurium, AlgA of Pseudomonas aeruginosa, and XanB of Xanthomonas campestris. The phylogenetic trees of PMM and GMP were different in topology and in the evolutionary distances from ancestors.

Synthesis of the K5 (group II) capsular polysaccharide in transport-deficient recombinant Escherichia coli

The genes directing the expression of group II capsules in Escherichia coli are organized into three regions. The central region 2 is type specific and thought to determine the synthesis of the respective polysaccharide, whilst the flanking regions 1 and 3 are common to all group II gene clusters and direct the surface expression of the capsular polysaccharide. In this communication we analyze the involvement of region 1 and 3 genes in the synthesis of the capsular KS polysaccharide. Recombinant E. coli strains harboring all KS specific region 2 genes and having various combinations of region 1 and 3 genes were studied using immunoelectron microscopy. Membranes from these bacteria were incubated with UDP[14C]GlcA and UDPGlcNAc in the absence or presence of KS polysaccharide as an exogenous acceptor. It was found that recombinant strains with only gene region 2 did not produce the K5 polysaccharide. Membranes of such strains did not synthesize the polymer and did not elongate K5 polysaccharide added as an exogenous acceptor. An involvement of genes from region 1 (notably kpsC and kpsS) and from region 3 (notably kpsT) in the K5 polysaccharide synthesis was apparent and is discussed.

Structural comparison of the O4-specific polysaccharides from E. coli O4:K6 and E. coli O4:K52

Two distinct forms of the O4 antigen (LPS) from E. coli were analysed by 1H and 13C NMR spectroscopy. Both consisted of D-glucose, L-rhamnose, 2-acetamido-2,6-dideoxy-L-galactose (L-FucNAc), and 2-acetamido-2-deoxy-D-glucose. Their structures were found to be [formula: see text]. In the O4-specific polysaccharide from E. coli O4:K3, O4:K6, and O4:K12, X is alpha-D-Glcp. In the O4 specific polysaccharide from E. coli O4:K52, the rhamnose residue is not substituted (X = H).

Structure of the O-specific polysaccharide of the O23 antigen (LPS) from Escherichia coli O23:K?:H16

The polysaccharide moiety of the O23 antigen (lipopolysaccharide) consists of D-glucose, D-galactose, 2-acetamido-2-deoxy-D-glucose, and 2-acetamido-2-deoxy-D-galactose in the molar ratios 2:1:2:1. Methylation analysis of the polysaccharide as well as one- and two-dimensional 1H and 13C NMR spectroscopy of the polysaccharide and a trisaccharide obtained by Smith degradation showed that the O23 polysaccharide has the primary structure [formula: see text].

Coexpression of colanic acid and serotype-specific capsular polysaccharides in Escherichia coli strains with group II K antigens

In Escherichia coli K-12, the rcsA and rcsB gene products are positive regulators in expression of the slime polysaccharide colanic acid. We have previously demonstrated the presence of rcsA sequences in E. coli K1 and K5, strains with group II capsular K antigens, and shown that introduction of multicopy rcsA into these strains results in the expression of colanic acid. We report here the presence of rcsB sequences in E. coli K1 and K5 and demonstrate that RcsB also plays a role in the biosynthesis of colanic acid in strains with group II K antigens. In E. coli K1 and K5 grown at 37 degrees C, multicopy rcsB and the resulting induction of colanic acid synthesis had no significant effect on synthesis of the group II K antigens. K-antigen-specific sugar transferase activities were not significantly different in the presence or absence of multicopy rcsB, and introduction of a cps mutation to eliminate colanic acid biosynthesis in a K1-derivative strain did not influence the activity of the polysialyltransferase enzyme responsible for synthesis of the K1 polymer. Furthermore, immunoelectron microscopy showed no detectable difference in the size or distribution of the group II K-antigen capsular layer in cells which produced colanic acid. Colanic acid expression therefore does not appear to significantly affect synthesis of the group II K-antigen capsule and, unlike for group I K antigens, expression of group II K antigens is not positively regulated by the rcs system.

[Computerized structural analysis of O-specific polysaccharides O1A, O1B, and O1C from Escherichia coli]

A computer evaluation of 13C-NMR data for the title polysaccharides based on the monosaccharide and methylation analysis data led to the structure of the repeating unit of the O1A polysaccharide as well as to several probable structures of the O1C polysaccharide, of which the correct one was inferred by means of a single NOE experiment. The analysis of the spectrum of the O1B polysaccharide was unsuccessful, due to the presence in its structure of the fragment alpha-L-Rha-(1-->2)-alpha-D-Gal-(1-->3)-D-GlcNAc with the terminal (1-->2)-linkage, whose spectral data could not be calculated by additive schemes using only glycosylation effects. However in reevaluation of the O1B spectral data by taking into account the deviations from additivities of the chemical shifts values in spectra of the related trisaccharides, to reveal the most probable structure of the O1B's repeating unit. [formula: see text]

Expression of the capsular K5 polysaccharide of Escherichia coli: biochemical and electron microscopic analyses of mutants with defects in region 1 of the K5 gene cluster

The gene cluster of the capsular K5 polysaccharide, a representative of group II capsular antigens of Escherichia coli, has been cloned previously, and three regions responsible for polymerization and surface expression have been defined (I.S. Roberts, R. Mountford, R. Hodge, K. B. Jann, and G. J. Boulnois, J. Bacteriol. 170:1305-1330, 1988). Region 1 has now been sequenced, and five open reading frames (kpsEDUCS) have been defined (C. Pazzani, C. Rosenow, G. J. Boulnois, D. Bronner, K. Jann, and I. S. Roberts, J. Bacteriol. 175:5978-5983, 1993). In this study, we characterized region 1 mutants by immunoelectron microscopy, membrane-associated polymerization activity, cytoplasmic CMP-2-keto-3-deoxyoctonate (KDO) synthetase activity, and chemical analysis of their K5 polysaccharides. Certain mutations within region 1 not only effected polysaccharide transport (lack of region 1 gene products) but also impaired the polymerization capacity of the respective membranes, reflected in reduced amounts of polysaccharide but not in its chain length. KDO and phosphatidic acid (phosphatidyl-KDO) substitution was found with extracellular and periplasmic polysaccharide and not with cytoplasmic polysaccharide. This and the fact that the K5 polysaccharide is formed in a kpsU mutant (defective in capsule-specific K-CMP-KDO synthetase) showed that CMP-KDO is engaged not in initiation of polymerization but in translocation of the polysaccharide.

Molecular analysis of region 1 of the Escherichia coli K5 antigen gene cluster: a region encoding proteins involved in cell surface expression of capsular polysaccharide

The nucleotide sequence of region 1 of the K5 antigen gene cluster of Escherichia coli was determined. This region is postulated to encode functions which, at least in part, participate in translocation of polysaccharide across the periplasmic space and onto the cell surface. Analysis of the nucleotide sequence revealed five genes that encode proteins with predicted molecular masses of 75.7, 60.5, 44, 43, and 27 kDa. The 27-kDa protein was 70.7% homologous to the CMP-2-keto-3-deoxyoctulosonic acid synthetase enzyme encoded by the E. coli kdsB gene, indicating the presence of a structural gene for a similar enzyme within the region 1 operon. The 43-kDa protein was homologous to both the Ctrb and BexC proteins encoded by the Neisseria meningitidis and Haemophilus influenzae capsule gene clusters, respectively, indicating common stages in the expression of capsules in these gram-negative bacteria. However, no homology was detected between the 75.7, 60.5-, and 44-kDa proteins and any of the proteins so far described for the H. influenzae and N. meningitidis capsule gene clusters.

Structure of the K10 capsular antigen from Escherichia coli O11:K10:H10, a polysaccharide containing 4,6-dideoxy-4-malonylamino-D-glucose

The K10 antigen from Escherichia coli O11:K10:H10 consists of equimolar amounts of rhamnose and 4,6-dideoxy-4-malonylaminoglucose [Qui4NMal; 4-(2-carboxyacetamido)-4,6-dideoxyglucose]. Methylation analysis and 1 and 2D NMR spectroscopy showed that the K10 capsular polysaccharide has the structure [formula: see text]

Genetic analysis of the gene cluster encoding nonfimbrial adhesin I from an Escherichia coli uropathogen

The chromosomally encoded nonfimbrial adhesion I (NFA-I) from Escherichia coli urinary tract isolate 827 (O83:K1:H4) mediates agglutination of human erythrocytes. Subclones were constructed from an NFA-I-expressing recombinant E. coli K-12 clone, derived from a genomic library of E. coli 827. Minicell analysis and nucleotide sequencing revealed that proteins of 30.5, 9, 80, 15, and 19 kDa encoded on a stretch of approximately 6 kb are involved in the expression of NFA-I. NFA-I exhibits a polymeric structure, which disintegrates with elevated temperature into a 19-kDa monomer but with some relatively stable dimers. By using gold-conjugated monoclonal antibodies directed against NFA-I in electron microscopy, the adhesin could be localized on the outer surface of the recombinant E. coli K-12 bacteria. The nucleotide sequence of the nfaA gene encoding the monomeric structural subunit of the adhesin was determined. An open reading frame of 184 amino acids encoding the NfaA precursor, which is processed to the mature protein, was found; it consisted of 156 amino acids with a calculated molecular weight of 16,000. Peptide sequencing of the NFA-I subunit protein confirmed that this open reading frame corresponds to the NfaA coding locus. Furthermore, the nucleotide sequence of the open reading frame termed NfaE, located at the proximal part of the DNA stretch responsible for NFA-I expression, was elaborated. NfaE consists of 247 amino acids, including a presumptive 29-amino-acid signal peptide, leading to a molecular weight of 24,000 for the mature protein. The nfaE sequence shares homology with the 27-kDa CS3 protein, which is involved in the assembly of CS3 fibrillae, and might encode the 30.5-kDa protein, detected in minicells.

Adhesion of S-fimbriated Escherichia coli to brain glycolipids mediated by sfaA gene-encoded protein of S-fimbriae

In an attempt to further assess the role of S-fimbriae in the pathogenesis of Escherichia coli meningitis, the adherence of E. coli strains with or without S-fimbriae were examined for this study to purified glycolipids using thin layer chromatography overlay assays. Only S-fimbriated E. coli strains bound to sulfatide, seminolipid, galactosyl ceramide, and lactosyl ceramide but not to gangliosides including sialyl neolacto-series and other neutral glycolipids. The binding of S-fimbriated E. coli to sulfatide was temperature dependent (i.e. maximal at 37 degrees C) and inhibited by S-fimbriae, anti-S-fimbriae, and anti-S-adhesin antibodies as well as by sulfatide, galactosyl ceramide, and lactosyl ceramide. E. coli transformants which lack the sfaA gene from the Sfa gene cluster showed no binding to the glycolipids, while other transformants lacking the adhesin gene sfaS or sfaG or H and mutants obtained by site-directed mutagenesis in the sfaS gene exhibited a similar binding to the glycolipids compared to the parent S-fimbriated strain. A large amount of sulfated glycolipids was demonstrated on brain endothelial cells and the binding of S-fimbriated E. coli to brain endothelial cells was inhibited by these glycolipids. These findings suggest that the binding of S-fimbriated E. coli to brain endothelial cells occurs in part via glycolipids containing terminal Gal(3SO4)beta-1 residues and in part by S-fimbriae protein SfaA. S-adhesin was not involved in the binding of S-fimbriae to these glycolipids.

Structural analysis of O4-reactive polysaccharides from recombinant Escherichia coli. Changes in the O-specific polysaccharide induced by cloning of the rfb genes

In previous studies it had been shown that lipopolysaccharide from O4-specific recombinant Escherichia coli, had serological reactivities and a chemical composition that differed from wildtype O4 LPS [Haraguchi, G.E., Zähringer, U., Jann, B., Jann, K., Hull, R.A. & Hull, S.I. (1991) Microb. Pathog. 10, 351-361]. Here we present the structural elucidation of the O-specific moieties from lipopolysaccharides of some of the recombinant strains obtained in previous studies. Compositional analysis, methylation, chemical reactions and NMR spectroscopy showed that, during genetic manipulations (recombination, cosmid cloning, plasmid subcloning), a gradual structural change in the O-specific polysaccharides was observed in the recombinant strains. These changes comprised of an alteration in the position of glucose (side chain) substitution, a change in the anomeric configuration of the main-chain N-acetylglucosamine and an exchange of alpha-L-rhamnopyranose for beta-D-galactofuranose. The relevance of these results for lipopolysaccharide cloning and lipopolysaccharide biosynthesis are discussed.

Cloning and characterization of the S fimbrial adhesin II complex of an Escherichia coli O18:K1 meningitis isolate

S fimbrial adhesins (Sfa), which are able to recognize sialic acid-containing receptors on eukaryotic cells, are produced by Escherichia coli strains causing urinary tract infections or newborn meningitis. We recently described the cloning and molecular characterization of a determinant, termed sfaI, from the chromosome of an E. coli urinary tract infection strain. Here we present data concerning a S fimbria-specific gene cluster, designated sfaII, of an E. coli newborn meningitis strain. Like the SfaI complex, SfaII consists of the major subunit protein SfaA (16 kDa) and the minor subunit proteins SfaG (17 kDa), SfaS (15 kDa), and SfaH (29 kDa). The genes encoding the subunit proteins of SfaII were identified and sequenced. Their protein sequences were calculated from the DNA sequences and compared with those of the SfaI complex subunits. Although the sequences of the two major SfaA subunits differed markedly, the sequences of the minor subunits showed only a few amino acid exchanges (SfaG, SfaH) or were completely identical (SfaS). The introduction of a site-specific mutation into the gene sfaSII and subsequent analysis of an SfaS-negative clone indicated that sfaSII codes for the sialic acid-specific adhesin of the meninigitis isolate. These data were confirmed by the isolation and characterization of the SfaSII protein and the determination of its N-terminal amino acid sequence. The identity between the sialic acid-specific adhesins of SfaI and SfaII revealed that differences between the two Sfa complexes with respect to their capacities to agglutinate erythrocytes must result from sequence alterations of subunit proteins other than SfaS.

Structure of the O56 antigen of Escherichia coli, a polysaccharide containing 7-substituted alpha-N-acetylneuraminic acid

The O56 polysaccharide moiety of the O56 antigen (LPS) consists of D-glucose, D-galactose, 2-acetamido-2-deoxy-D-glucose, and N-acetylneuraminic acid in the molar ratios 1:1:1:1. Methylation analysis, periodate oxidation, mild acid hydrolysis, as well as 1H and 13C NMR spectroscopy showed that the O56 polysaccharide has the primary structure [formula: see text]

Structures of the O1B and O1C lipopolysaccharide antigens of Escherichia coli

The O-specific moieties of the O1B antigen (lipopolysaccharide) from Escherichia coli O1B:K1 and the O1C antigen from E. coli O1C:K- both consist of L-rhamnose, D-galactose, N-acetyl-D-glucosamine, and N-acetyl-D-mannosamine in a molar ratio of 2:1:1:1. By using fragmentation procedures, methylation analysis, and one- and two-dimensional nuclear magnetic resonance spectroscopy, the structures of these polysaccharides were found to be [formula: see text] In the O1B polysaccharide X is 2, and in the O1C polysaccharide X is 3. With the recently published structure of the O1A polysaccharides (B. Jann, A. S. Shashkov, D. S. Gupta, S. M. Panasenko, and K. Jann, Carbohydr. Polym. 18:51-57 1992), three related O1 antigens are now known. Their common (O1-specific) epitope is suggested to be the side-chain N-acetyl-D-mannosamine residue.