Role of the rfe gene in the synthesis of the O8 antigen in Escherichia coli K-12.

The Escherichia coli O8 antigen is a mannan composed of the trisaccharide repeat unit -->3)-alpha-Man-(1-->2)-alpha-Man-(1-->2)-alpha-Man-(1--> (K. Reske and K. Jann, Eur. J. Biochem. 67:53-56, 1972), and synthesis of the O8 antigen is rfe dependent (G. Schmidt, H. Mayer, and P. H. Mäkelä, J. Bacteriol. 127:755-762, 1976). The rfe gene has recently been identified as encoding a tunicamycin-sensitive UDP-GlcNAc:undecaprenylphosphate GlcNAc-1-phosphate transferase (U. Meier-Dieter, K. Barr, R. Starman, L. Hatch, and P. D. Rick, J. Biol. Chem. 267:746-753, 1992). However, the role of rfe in O8 side chain synthesis is not understood. Thus, the role of the rfe gene in the synthesis of the O8 antigen was investigated in an rfbO8+ (rfb genes encoding O8 antigen) derivative of E. coli K-12 mutant possessing a defective phosphoglucose isomerase (pgi). The in vivo synthesis of O8 side chains was inhibited by the antibiotic tunicamycin. In addition, putative lipid carrier-linked O8 side chains accumulated in vivo when lipopolysaccharide outer core synthesis was precluded by growing cells in the absence of exogenously supplied glucose. The lipid carrier-linked O8 antigen was extracted from cells and treated with mild acid in order to release free O8 side chains. The water-soluble O8 side chains were then purified by affinity chromatography using Sepharose-bound concanavalin A. Characterization of the affinity-purified O8 side chains revealed the occurrence of glucosamine in the reducing terminal position of the polysaccharide chains. The data presented suggest that GlcNAc-pyrophosphorylundecaprenol functions as the acceptor of mannose residues for the in vivo synthesis of O8 side chains in E. coli K-12.     

Presence of rfe genes in Escherichia coli: their participation in biosynthesis of O antigen and enterobacterial common antigen.

In Salmonella, ilv-linked rfe genes participate in the biosynthesis of the enterobacterial common antigen (CA) as well as of certain types of O antigen (serogroups C1 and L). rff genes, probably in the same cluster with rfe, are required for CA synthesis (P.H. M?kel? et al., in preparation). Several Escherichia coli strains were studied to determine whether they also have rfe-rff genes that are involved in the synthesis of O antigen and CA, or of CA only. In a first approach, E, coli K-12 F-prime factors carrying the genes ilv and argH or argE and presumably rfe-rff genes were introduced into CA-negative Salmonella mutants that are blocked in CA synthesis because of mutated rfe or rff genes. All resulting ilv+ hybrids were CA positive. In recipients with group C1-derived rfb genes, the synthesis of O6,7-specific antigen was also restored. This result shows that E. coli K-12 has rfe and rff genes providing the functions required in the synthesis of CA and Salmonella 6,7-specific polysaccharide. By introduction of defective rfe regions from suitable Salmonella donors into E. coli O8, 09, and O100 strains, the synthesis of CA as well as of the O-specific polysaccharides was blocked. This indicates that in the E. coli strains tested the rfe genes are involved in the synthesis of both O antigen and CA. This suggestion was confirmed by the finding of E. coli rough mutants that had simultaneously become CA negative. In transduction experiments it could be shown that the appearance of the rough and CA- phenotype was due to a defect in the ilv-linked rfe region.     

Participation of Lipopolysaccharide Genes in the Determination of the Enterobacterial Common Antigen: Analysis of R Mutants of Salmonella minnesota

A series of R (rough) Salmonella minnesota mutants with rfb, rfe, and rfa mutations leading to various defects in the biosynthesis of cell wall lipopolysaccharide was analyzed as to their enterobacterial common antigen (CA) content. All mutants that had functional rfe genes were CA(+) as is the wild-type parent. This includes mutants with the most defective lipopolysaccharide core types, demonstrating that core structures are not a necessary part of CA. All rfe(-) mutants (complete lipopolysaccharide core, defective synthesis of O side chains) were defective in the synthesis of CA. A smooth strain was accidentally found to be CA(-); the mutation responsible for this defect was also located, like rfe, very close to ilv.     

Cloning and expression of the rfe–rff gene cluster of Escherichia coli

We have cloned a 13 kb Escherichia coli DNA fragment which complemented the rfe mutation to recover the biosynthesis of E. coli O9 polysaccharide. Using Tn5 insertion inactivation, the rfe gene was localized at the 1.5 kb HindIII-EcoRI region flanking the rho gene. We constructed an rfe-deficient E. coli K-12 mutant by site-directed inactivation using a DNA fragment of the cloned 1.5 kb rfe gene. This also confirmed the presence of the rfe gene in the 1.5 kb region. By simultaneous introduction of both the rfe plasmid and the plasmid of our previously cloned E. coli O9 rfb into this rfe mutant, we succeeded in achieving in vivo reconstitution of O9 polysaccharide biosynthesis. From sequence analysis of the rfe gene, a putative promoter followed by an open reading frame (ORF) was identified downstream of the rho gene. This ORF coincided with the position of the rfe gene determined by Tn5 analysis and site-directed mutagenesis. Furthermore, we identified the rff genes in the 10.5 kb DNA flanking the rfe gene. We recognized at least two functional domains on this cloned rff region. Region I complemented a newly found K-12 rff mutant, A238, to synthesize the enterobacterial common antigen (ECA). Deletion of region II resulted in the synthesis of ECAs with shorter sugar chains. When the 10.5 kb rff genes of the plasmid were inactivated by either deletion or Tn5 insertion, the plasmid lost its ability to give rise to transformants of the rfe mutants.     

The core region of Proteus mirabilis R110/1959 lipopolysaccharide

The complete core structure present in the lipopolysaccharide of the R mutant R110/1959 from Proteus mirabilis (Proteus type II core) was investigated using methylation analysis and a number of degradation methods such as Smith degradation and beta-elimination. These studies combined with earlier work on a Rc-type mutant of P. mirabilis O28 (R4/O28) which shares the same inner core region, allowed formulation of the complete core structure of the Proteus type II core as shown in Scheme 1. (formula; see text) A characteristic feature of the Proteus core of type II is the presence of two units of D-galacturonic acid (DGalA); one in terminal, the other one in a chain-linked position. In addition, the presence of the two isomers of glycero-D-manno-heptose (LDHep and DDHep) and the lack of galactose are conspicuous. DDHep occupies a terminal position in the external core region, whereas the three units of LDHep in addition to dOclA form, as in other enterobacterial core types, the internal core region. The taxonomic significance of the presence of DGalA in the Proteus type II core, but also in all R cores of other Proteeae investigated so far, will be discussed.     

Evidence that WapB is a 1,2-glucosyltransferase of Pseudomonas aeruginosa involved in Lipopolysaccharide outer core biosynthesis

Pseudomonas aeruginosa is an important opportunistic pathogen infecting debilitated individuals. One of the major virulence factors expressed by P. aeruginosa is lipopolysaccharide (LPS), which is composed of lipid A, core oligosaccharide (OS), and O-antigen polysaccharide. The core OS is divided into inner and outer regions. Although the structure of the outer core OS has been elucidated, the functions and mechanisms of the glycosyltransferases involved in core OS biogenesis are currently unknown. Here, we show that a previously uncharacterized gene, pa1014, is involved in outer core biosynthesis, and we propose to rename this gene wapB. We constructed a chromosomal mutant, wapB::Gm, in a PAO1 (O5 serotype) strain background. Characterization of the LPS from the mutant by Western immunoblotting showed a lack of reactivity to PAO1 outer core-specific monoclonal antibody (MAb) 5c-101. The chemical structure of the core OS of the wapB mutant was elucidated using nuclear magnetic resonance spectroscopy and mass spectrometry techniques and revealed that the core OS of the wapB mutant lacked the terminal β-1,2-linked-d-glucose residue. Complementation of the mutant with wapB in trans restored the core structure to one that is identical to that of the wild type. Eleven of the 20 P. aeruginosa International Antigenic Typing Scheme (IATS) serotypes produce LPSs that lack the terminal d-glucose residue (Glc(IV)). Interestingly, expressing wapB in each of these 11 serotypes modifies each of their outer core OS structures, which became reactive to MAb 5c-101 in Western immunoblotting, suggesting the presence of a terminal d-glucose in these core OS structures. Our results strongly suggested that wapB encodes a 1,2-glucosyltransferase.     

Role of the rfe gene in the biosynthesis of the Escherichia coli O7-specific lipopolysaccharide and other O-specific polysaccharides containing N-acetylglucosamine.

We report that rfe mutants of wild-type strains of Escherichia coli O7, O18, O75, and O111 did not express O-specific polysaccharide unless the rfe mutation was complemented by a cloned rfe gene supplied in a plasmid. The O polysaccharides in these strains are known to have N-acetylglucosamine (GlcNAc) in their O repeats. In addition, in vitro transferase assays with bacterial membranes from either the O7 wild-type strain or its isogenic rfe mutant showed that GlcNAc is the first carbohydrate added onto the lipid acceptor in the assembly of the O7 repeat and that this function is inhibited by tunicamycin. Our results indicate that the rfe gene product is a general requirement for the synthesis of O polysaccharides containing GlcNAc.     

The Pseudomonas aeruginosa algC gene encodes phosphoglucomutase, required for the synthesis of a complete lipopolysaccharide core.

We have constructed strains of Pseudomonas aeruginosa with mutations in the algC gene, previously shown to encode the enzyme phosphomannomutase. The algC mutants of a serotype O5 strain (PAO1) and a serotype O3 strain (PAC1R) did not express lipopolysaccharide (LPS) O side chains or the A-band (common antigen) polysaccharide. The migration of LPS from the algC mutant strains in Tricine-sodium dodecyl sulfate-polyacrylamide gels was similar to that of LPS from a PAO1 LPS-rough mutant, strain AK1012, and from a PAC1R LPS-rough mutant, PAC605, each previously shown to be deficient in the incorporation of glucose onto the LPS core (K. F. Jarrell and A. M. Kropinski, J. Virol. 40:411-420, 1981, and P. S. N. Rowe and P. M. Meadow, Eur. J. Biochem. 132:329-337, 1983). We show that, as expected, the algC mutant strains had no detectable phosphomannomutase activity and that neither algC strain had detectable phosphoglucomutase (PGM) activity. To confirm that the PGM activity was encoded by the algC gene, we transferred the cloned, intact P. aeruginosa algC gene to a pgm mutant of Escherichia coli and observed complementation of the pgm phenotype. Our finding that the algC gene product has PGM activity and that strains with mutations in this gene produce a truncated LPS core suggests that the synthesis of glucose 1-phosphate is necessary in the biosynthesis of the P. aeruginosa LPS core. The data presented here thus demonstrate that the algC gene is required for the synthesis of a complete LPS core in two strains with different LPS core and O side chain structures.     

Nucleotide sequence of the Escherichia coli rfe gene involved in the synthesis of enterobacterial common antigen. Molecular cloning of the rfe-rff gene cluster.

The genetic determinants of enterobacterial common antigen (ECA) include the rfe and rff genes located between ilv and cya near min 85 on the Escherichia coli chromosome. The rfe-rff gene cluster of E. coli K-12 was cloned in the cosmid pHC79. The cosmid clone complemented mutants defective in the synthesis of ECA due to lesions in the rfe, rffE, rffD, rffA, rffC, rffT, and rffM genes. Restriction endonuclease mapping combined with complementation studies of the original cosmid clone and six subclones revealed the order of genes in this region to be rfe-rffD/rffE-rffA/rffC-rffT-rffM . The rfe gene was localized to a 2.54-kilobase ClaI fragment of DNA, and the complete nucleotide sequence of this fragment was determined. The nucleotide sequencing data revealed two open reading frames, ORF-1 and ORF-2, located on the same strand of DNA. The putative initiation codon of ORF-1 was found to be 570 nucleotides downstream from the termination codon of rho. ORF-1 and ORF-2 specify putative proteins of 257 and 348 amino acids with calculated Mr values of 29,010 and 39,771, respectively. ORF-1 was identified as the rfe gene since ORF-1 alone was able to complement defects in the synthesis of ECA and 08-side chain synthesis in rfe mutants of E. coli. Data are also presented which suggest the possibility that the rfe gene is the structural gene for the tunicamycin sensitive UDP-GlcNAc:undecaprenylphosphate GlcNAc-1-phosphate transferase that catalyzes the synthesis of GlcNAc-pyrophosphorylundecaprenol (lipid I), the first lipid-linked intermediate involved in ECA synthesis.     

Role of a lipopolysaccharide gene for immunogenicity of the enterobacterial common antigen.

It is known that only certain strains of the family of Enterobacteriaceae, notably rough (R) mutants with the type R1 or R4 core, evoked antibodies in high titers against the common enterobacterial antigen (CA) after immunization of rabbits with heated cell suspensions. The present investigation deals with genetic and immunochemical aspects of certain R1 and R4 mutants isolated from Escherichia coli 08 and various Shigella serotypes which, unexpectedly, do not induce CA antibody formation. Immunochemical and genetical (transduction and conjugation) experiments revealed that the rough phenotype of these special mutants was evoked by a mutation of pyrE-linked rfa gene, called rfaL, which is involved in translocation of O-specific polysaccharides onto the lipopolysaccharide core. The transduction of the defective rfaL, allele into appropriate rough recipients results in transductants which have simultaneously lost the ability to evoke CA antibodies. This finding suggests that a close connection exists between the function of the rfaL gene and the expression of CA immunogenicity in R1 and R4 mutants. One of the strains synthesized neither O-hapten nor CA, suggesting a mutation in a region equivalent to the rfe genes of Salmonella.     

Identification of a cross-reactive epitope widely present in lipopolysaccharide from enterobacteria and recognized by the cross-protective monoclonal antibody WN1 222-5

Septic shock due to infections with Gram-negative bacteria is a severe disease with a high mortality rate. We report the identification of the antigenic determinants of an epitope that is present in enterobacterial lipopolysaccharide (LPS) and recognized by a cross-reactive monoclonal antibody (mAb WN1 222-5) regarded as a potential means of treatment. Using whole LPS and a panel of neoglycoconjugates containing purified LPS oligosaccharides obtained from Escherichia coli core types R1, R2, R3, and R4, Salmonella enterica, and the mutant strain E. coli J-5, we showed that mAb WN1 222-5 binds to the distal part of the inner core region and recognizes the structural element R1-alpha-d-Glcp-(1-->3)-[l-alpha-d-Hepp-(1-->7)]-l-alpha-d-Hepp 4P-(1-->3)-R2 (where R1 represents additional sugars of the outer core and R2 represents additional sugars of the inner core), which is common to LPS from all E. coli, Salmonella, and Shigella. WN1 222-5 binds poorly to molecules that lack the side chain heptose or lack phosphate at the branched heptose. Also molecules that are substituted with GlcpN at the side chain heptose are poorly bound. Thus, the side chain heptose and the 4-phosphate on the branched heptose are main determinants of the epitope. We have determined the binding kinetics and affinities (KD values) of the monovalent interaction of E. coli core oligosaccharides with WN1 222-5 by surface plasmon resonance and isothermal titration microcalorimetry. Affinity constants (KD values) determined by SPR were in the range of 3.6 x 10-5 to 3.2 x 10-8 m, with the highest affinity being observed for the core oligosaccharide from E. coli F576 (R2 core type) and the lowest KD values for those from E. coli J-5. Affinities of E. coli R1, R3, and R4 oligosaccharides were 5-10-fold lower, and values from the E. coli J-5 mutant were 29-fold lower than the R2 core oligosaccharide. Thus, the outer core sugars had a positive effect on binding.     

The role of galacturonic acid in outer membrane stability in Klebsiella pneumoniae

In most members of the Enterobacteriaceae, including Escherichia coli and Salmonella, the lipopolysaccharide core oligosaccharide backbone is modified by phosphoryl groups. The negative charges provided by these residues are important in maintaining the barrier function of the outer membrane. Mutants lacking the core heptose region and the phosphate residues display pleiotrophic defects collectively known as the deep-rough phenotype, characterized by changes in outer membrane structure and function. Klebsiella pneumoniae lacks phosphoryl residues in its core, but instead contains galacturonic acid. The goal of this study was to determine the contribution of galacturonic acid as a critical source of negative charge. A mutant was created lacking all galacturonic acid by targeting UDP-galacturonic acid precursor synthesis through a mutation in gla(KP). Gla(KP) is a K. pneumoniae UDP-galacturonic acid C4 epimerase providing UDP-galacturonic acid for core synthesis. The gla(KP) gene was inactivated and the structure of the mutant lipopolysaccharide was determined by mass spectrometry. The mutant displayed characteristics of a deep-rough phenotype, exhibiting a hypersensitivity to hydrophobic compounds and polymyxin B, an altered outer membrane profile, and the release of the periplasmic enzyme beta-lactamase. These results indicate that the negative charge provided by the carboxyl groups of galacturonic acid do play an equivalent role to the core oligosaccharide phosphate residues in establishing outer membrane integrity in E. coli and Salmonella.     

Effect of miconazole on the structure and function of plasma membrane of Candida albicans

Abstract Fructose, a rarely occurring sugar constituent of Gram-negative bacterial lipopolysaccharides (LPS), is distributed ubiquitously in LPS of 01 Vibrio cholerae so far examined, but its location in LPS has not hitherto been elucidated. It was found that hydrazinolysis of LPS successfully affords a derivative retaining virtually all the fructose of intact LPS, but no ester-bound phosphate. Structural analysis carried out on the LPS derivative prepared by the hydrazinolysis of R-type LPS isolated from a rough mutant strain (NIH 41R) of 01 V. cholerae NIH 41 (Ogawa) revealed that the fructose is present as a non-reducing terminal residue bound to position C-6 of a glucose residue in the core region. This finding is considered to exclude the possibility that, in the LPS of 01 V. cholerae , the fructose is present in the region of the inner core in place of 2-keto-3-deoxyoctonate.     

Biosynthesis of a novel 3-deoxy-D-manno-oct-2-ulosonic acid-containing outer core oligosaccharide in the lipopolysaccharide of Klebsiella pneumoniae

The core oligosaccharide region of Klebsiella pneumoniae lipopolysaccharide contains some novel features that distinguish it from the corresponding lipopolysaccharide region in other members of the Enterobacteriaceae family, such as Escherichia coli and Salmonella. The conserved Klebsiella outer core contains the unusual trisaccharide 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo)-(2,6)-GlcN-(1,4)-GalUA. In general, Kdo residues are normally found in the inner core, but in K. pneumoniae, this Kdo residue provides the ligation site for O polysaccharide. The outer core Kdo residue can also be non-stoichiometrically substituted with an l-glycero-d-manno-heptopyranose (Hep) residue, another component more frequently found in the inner core. To understand the genetics and biosynthesis of core oligosaccharide synthesis in Klebsiella, the gene products involved in the addition of the outer core GlcN (WabH), Kdo (WabI), and Hep (WabJ) residues as well as the inner core HepIII residue (WaaQ) were identified. Non-polar mutations were created in each of the genes, and the resulting mutant lipopolysaccharide was analyzed by mass spectrometry. The in vitro glycosyltransferase activity of WabI and WabH was verified. WabI transferred a Kdo residue from CMP-Kdo onto the acceptor lipopolysaccharide. The activated precursor required for GlcN addition has not been identified. However, lysates overexpressing WabH were able to transfer a GlcNAc residue from UDP-GlcNAc onto the acceptor GalUA residue in the outer core.     

Truncation of the lipopolysaccharide outer core affects susceptibility to antimicrobial peptides and virulence of Actinobacillus pleuropneumoniae serotype 1

We reported previously that the core oligosaccharide region of the lipopolysaccharide (LPS) is essential for optimal adhesion of Actinobacillus pleuropneumoniae, an important swine pathogen, to respiratory tract cells. Rough LPS and core LPS mutants of A. pleuropneumoniae serotype 1 were generated by using a mini-Tn10 transposon mutagenesis system. Here we performed a structural analysis of the oligosaccharide region of three core LPS mutants that still produce the same O-antigen by using methylation analyses and mass spectrometry. We also performed a kinetic study of proinflammatory cytokines production such as interleukin (IL)-6, tumor necrosis factor-alpha, IL1-beta, MCP-1, and IL8 by LPS-stimulated porcine alveolar macrophages, which showed that purified LPS of the parent strain, the rough LPS and core LPS mutants, had the same ability to stimulate the production of cytokines. Most interestingly, an in vitro susceptibility test of these LPS mutants to antimicrobial peptides showed that the three core LPS mutants were more susceptible to cationic peptides than both the rough LPS mutant and the wild type parent strain. Furthermore, experimental pig infections with these mutants revealed that the galactose (Gal I) and d,d-heptose (Hep IV) residues present in the outer core of A. pleuropneumoniae serotype 1 LPS are important for adhesion and overall virulence in the natural host, whereas deletion of the terminal GalNAc-Gal II disaccharide had no effect. Our data suggest that an intact core-lipid A region is required for optimal protection of A. pleuropneumoniae against cationic peptides and that deletion of specific residues in the outer LPS core results in the attenuation of the virulence of A. pleuropneumoniae serotype 1.     

Biosynthesis of enterobacterial common antigen requires dTDPglucose pyrophosphorylase determined by a Salmonella typhimurium rfb gene and a Salmonella montevideo rfe gene.

In group C1 salmonellae, rfe and rff genes linked to the ilv locus specify the synthesis of a glycolipid called the enterobacterial common antigen. In contrast, in group B salmonellae the synthesis requires in addition some of the genes in the rfb cluster, the main genetic determinant of the O side chains of lipopolysaccharide. In an effort to define the biochemical functions of these rfb genes, we looked in Salmonella typhimurium LT2 (group B) for rfb mutants in which the synthesis of both enterobacterial common antigen and the O side chains would be blocked in a manner suppressible by the wild-type rfe cluster of S. montevideo, of group C1. We found one mutant with these characteristics. This rfb mutation affected the activity of dTDPglucose pyrophosphorylase (glucose-1-phosphate thymidylyltransferase, EC 2.7.7.24). Whereas the rfe cluster of S. montevideo contained a gene producing this enzyme activity, there was no evidence for the presence of such a gene in the rfe cluster of group B strains. These results also showed that the synthesis of dTDP-glucose is necessary for the biosynthesis of enterobacterial common antigen; this conclusion fits with the recent demonstration of 4-acetamido-4,6-dideoxy-D-galactose as a component of enterobacterial common antigen (Lugowski et al., Carbohydr. Res. 118:173-181, 1983), because the biosynthesis of the donor of this sugar, dTDP-4-acetamido-4,6-dideoxy-D-galactose, requires dTDPglucose pyrophosphorylase.     

Participation of Lipopolysaccharide Genes in the Determination of the Enterobacterial Common Antigen: Analysis in Salmonella Groups B and C1

The enterobacterial common antigen (CA) is present in salmonellae of groups B (S. typhimurium) and C(1) (S. montevideo). Mutation at the rfe gene(s), which is required for the biosynthesis of O side chains of the lipopolysaccharide in group C(1) (S-6, 7) but not in group B (S-4, 12), destroys the capacity of the bacteria to synthesize CA. When such mutated group C(1)rfe genes (C-rfe(-)) were introduced into group B strains, the hybrids also became CA(-) and could be restored to CA(+) by introduction of either C-rfe(+) or B-rfe(+) (corresponding genetic region in group B). This indicated the presence of genes for CA synthesis at the rfe site in both groups B and C(1). In rfe(-) mutants of group C(1), which were rough and CA(-), the CA(+) phenotype could be restored by replacing the rfe(-) gene(s) with C-rfe(+). In contrast, B-rfe(+) was able to support the synthesis of trace amounts of CA only, although it was sufficient to restore their ability to synthesize the S-6, 7 side chain of the lipopolysaccharide. Corresponding hybrids (B-rfe(+), C-rfb(+) or C-rfb(-)) were constructed by introducing the C-rfb genes into a group B strain; they also showed only a trace of CA reactivity.     

Characterization of chimeric lipopolysaccharides from Escherichia coli strain JM109 transformed with lipooligosaccharide synthesis genes (lsg) from Haemophilus influenzae

Previously, we reported the expression of chimeric lipopolysaccharides (LPS) in Escherichia coli strain JM109 (a K-12 strain) transformed with plasmids containing Haemophilus influenzae lipooligosaccharide synthesis genes (lsg) (Abu Kwaik, Y., McLaughlin, R. E., Apicella, M. A., and Spinola, S. M. (1991) Mol. Microbiol. 5, 2475-2480). In this current study, we have analyzed the O-deacylated LPS and free oligosaccharides from three transformants (designated pGEMLOS-4, pGEMLOS-5, and pGEMLOS-7) by matrix-assisted laser desorption ionization, electrospray ionization, and tandem mass spectrometry techniques, along with composition and linkage analyses. These data show that the chimeric LPS consist of the complete E. coli LPS core structure glycosylated on the 7-position of the non-reducing terminal branch heptose with oligosaccharides from H. influenzae. In pGEMLOS-7, the disaccharide Gal1--> 3GlcNAc1--> is added, and in pGEMLOS-5, the structure is extended to Gal1-->4GlcNAc1-->3Gal1-->3GlcNAc1-->. PGEMLOS-5 LPS reacts positively with monoclonal antibody 3F11, an antibody that recognizes the terminal disaccharide of lacto-N-neotetraose. In pGEMLOS-4 LPS, the 3F11 epitope is apparently blocked by glycosylation on the 6-position of the terminal Gal with either Gal or GlcNAc. The biosynthesis of these chimeric LPS was found to be dependent on a functional wecA (formerly rfe) gene in E. coli. By using this carbohydrate expression system, we have been able to examine the functions of the lsg genes independent of the effects of other endogenous Haemophilus genes and expressed proteins.     

The cell wall receptor for bacteriophage Mu G(−) in Erwinia and Escherichia coli C

Abstract Adsorption of bacteriophage Mu with its invertible DNA segment in the G(−) orientation requires a terminal glucose residue for binding to the core lipopolysaccharide (LPS) of Gram-negative bacteria. Analysis of a Mu-resistant mutant shows that the receptor for Mu G(−) in Erwinia B374 is a Glc-β1,6-Glc disaccharide. A spontaneously occurring host-range mutant, Mu G(−)h101, grows on Escherichia coli C. The loss of the terminal β1,3-linked glucose from the LPS of E. coli C leads to resistance to the phage Mu. These mutants are also resistant to phage P1 and D108 which have largely homologous G segments. This shows that Mu G(+) and G(−) phage particles differ with respect to their cell-wall receptors in the type of glycosidic linkage of a terminal glucose residue: α1, 2 for G(+) and β1,6 for G(−).