Purification and chemical characterization of type 1 pili isolated from Klebsiella pneumoniae

Inactivation of the virulence factors from 2,3-butanediol-producing Klebsiella pneumoniae

The microbiological production of 2,3-butanediol (2,3-BDO) has attracted considerable attention as an alternative way to produce high-value chemicals from renewable sources. Among the number of 2,3-BDO-producing microorganisms, Klebsiella pneumoniae has been studied most extensively and is known to produce large quantity of 2,3-BDO from a range of substrates. On the other hand, the pathogenic characteristics of the bacteria have limited its industrial applications. In this study, two major virulence traits, outer core LPS and fimbriae, were removed through homologous recombination from 2,3-BDO-producing K. pneumoniae 2242 to expand its uses to the industrial scale. The K. pneumoniae 2242 ∆wabG mutant strain was found to have an impaired capsule, which significantly reduced its ability to bind to the mucous layer and evade the phagocytic activity of macrophage. The association with the human ileocecal epithelial cell, HCT-8, and the bladder epithelial cell, T-24, was also reduced dramatically in the K. pneumoniae 2242 ∆fimA mutant strain that was devoid of fimbriae. However, the growth rate and production yield for 2,3-BDO were unaffected. The K. pneumoniae strains developed in this study, which are devoid of the major virulence factors, have a high potential for the efficient and sustainable production of 2,3-BDO.

Optimal method for efficiently removing extracellular nanofilaments from Shewanella oneidensis MR-1

The identification, production, and potential electron conductivity of bacterial extracellular nanofilaments is an area of great study, specifically in Shewanella oneidensis MR-1. While some studies focus on nanofilaments attached to the cellular body, many studies require the removal of these nanofilaments for downstream applications. The removal of nanofilaments from S. oneidensis MR-1 for further study requires not only that the nanofilaments be detached, but also for the cell bodies to remain intact. This is a study to both qualitatively (AFM) and quantitatively (LC/MS-MS) assess several nanofilament shearing methods and determine the optimal procedure. The best method for nanofilament removal, as judged by maximizing extracellular filamentous proteins and minimizing membrane and intracellular proteins, is vortexing a washed cell culture for 10 min.

Phenotypic characterization of human pathogenic bacteria in fish from the coastal waters of South West Cameroon: public health implications

Increasing economic and recreational opportunities, attractive scenery and a perception of a better quality of life are luring people to the coast. Unfortunately, these activities together with the commensurate increase in population in the area inevitably result in pollution of coastal waters with excessive microorganisms and other pollutants. Microbial pollutants not only contaminate the coastal water but also aquatic food sources, thus posing a health risk to consumers. Fish is a major source of protein in Cameroon, especially in the coastal areas. In this study, we investigated the microbiological quality of fish from the Limbe and Tiko beaches in South West Cameroon from May to October 2007. We isolated human pathogenic bacteria from three anatomic sites (skin, gills, intestine) of 50 fish (150 specimens) and investigated their susceptibility patterns to a battery of antibiotics. Data were analyzed statistically using chi2 with significance set at p < .05. Eleven bacterial species were identified, including Escherichia coli type 1 (20.8%), Citrobacter fruendii (16.4%), Proteus vulgaris (13%), Klebsiella pneumoniae (12.1%), Klebsiella ozaenae (7.7%), Enterobacter cloacae (7.2%), Klebsiella oxytoca (5.8%), Serratia marcescens (4.8%), Serratia odorifera (4.8%), Hafnia alvei (4.4%) and Proteus penneri (2.9%). More contaminated fish were found at Limbe beach than at Tiko beach (61.4% versus 38.6%, respectively (p < .05)). When ranking contamination with respect to anatomic site, skin was the most contaminated (40.6%) specimen and gills the least (28.5%). Ciprofloxacillin, ofloxacillin, and cotrimoxazole were the most effective antibiotics against all isolates, exhibiting 100% sensitivity. Almost half of the isolates (45.7%) were resistant to ampicillin. The results of our study demonstrate that fish from the coastal waters of South West Cameroon are a source of human pathogenic and opportunistic bacteria; hence this finding has public health implications.

PssO, a unique extracellular protein important for exopolysaccharide synthesis in Rhizobium leguminosarum bv. trifolii

Synthesis and secretion of polysaccharides by Gram-negative bacteria are a result of a concerted action of enzymatic and channel-forming proteins localized in different compartments of the cell. The presented work comprises functional characterization of PssO protein encoded within the previously identified, chromosomal exopolysaccharide (EPS) biosynthesis region (Pss-I) of symbiotic bacterium Rhizobium leguminosarum bv. trifolii TA1 (RtTA1). pssO gene localization between pssN and pssP genes encoding proteins engaged in exopolysaccharide synthesis and transport, suggested its role in EPS synthesis and/or secretion. RtTA1 pssO deletion mutant and the PssO protein overproducing strains were constructed. The mutant strain was EPS-deficient, however, this mutation was not complemented. The PssO-overproducing strain was characterized by increase in EPS secretion. Subcellular fractionation, pssO-phoA/lacZ translational fusion analyses and immunolocalisation of PssO on RtTA1 cell surface by electron microscopy demonstrated that PssO is secreted to the extracellular medium and remains attached to the cell. Western blotting analysis revealed the presence of immunologically related proteins within the species R. leguminosarum bv. trifolii, bv. viciae and Rhizobium etli. The secondary structure of PssO-His(6), as determined by FTIR spectroscopy, consists of at least 32% alpha-helical and 12% beta-sheet structures. A putative function of PssO in EPS synthesis and/or transport is discussed in the context of its cellular localization and the phenotypes of the deletion mutant and pssO-overexpressing strain.

Utilization of an intracellular bacterial community pathway in Klebsiella pneumoniae urinary tract infection and the effects of FimK on type 1 pilus expression

Klebsiella pneumoniae is an important cause of urinary tract infection (UTI), but little is known about its pathogenesis in vivo. The pathogenesis of the K. pneumoniae cystitis isolate TOP52 was compared to that of the uropathogenic Escherichia coli (UPEC) isolate UTI89 in a murine cystitis model. Bladder and kidney titers of TOP52 were lower than those of UTI89 at early time points but similar at later time points. TOP52, like UTI89, formed biofilm-like intracellular bacterial communities (IBCs) within the murine bladder, albeit at significantly lower levels than UTI89. Additionally, filamentation of TOP52 was observed, a process critical for UTI89 evasion of neutrophil phagocytosis and persistence in the bladder. Thus, the IBC pathway is not specific to UPEC alone. We investigated if differences in type 1 pilus expression may explain TOP52's early defect in vivo. The type 1 pilus operon is controlled by recombinase-mediated (fimE, fimB, and fimX) phase variation of an invertible promoter element. We found that K. pneumoniae carries an extra gene of unknown function at the 3' end of its type 1 operon, fimK, and the genome lacks the recombinase fimX. A deletion mutant of fimK was constructed, and TOP52 Delta fimK had higher titers and formed more IBCs in the murine cystitis model than wild type. The loss of fimK or expression of E. coli fimX from a plasmid in TOP52 resulted in a larger phase-ON population and higher expression levels of type 1 pili and gave TOP52 the ability to form type 1-dependent biofilms. Complementation with pfimK decreased type 1 pilus expression and biofilm formation of TOP52 Delta fimK and decreased UTI89 biofilm formation. Thus, K. pneumoniae appears programmed for minimal expression of type 1 pili, which may explain, in part, why K. pneumoniae is a less prevalent etiologic agent of UTI than UPEC.

Detecting Bacteria by Direct Counting of Structural Protein Units by IVDS and Mass Spectrometry

This report explores the direct counting of "hair-like" struc-tures specific for Gram-positive bacteria. Indications show that these structures are intact after removal from the cell and are sufficiently different from species to species of bacteria to give an indication of bacteria type if not actual identification. Their detection would represent a new approach to bacteria detection and identification. This report documents the detection of the bacterial structures using the physical nanometer counting methodology in the Integrated Virus Detection System (IVDS) and electrospray ionization-mass spectrometry.

Major structural proteins of type 1 and type 3 Klebsiella fimbriae are effective protein carriers and immunogens in conjugates as revealed from their immunochemical characterization

Fimbriae are filamentous structures present on the cell surface of many bacteria, including genus Klebsiella. The use of fimbriae as protein carriers in conjugates may allow to formulate effective multivalent vaccines and suitable diagnostics. However, the evidences have been reported that fimbriae may enhance the inflammatory response. This prompted us to examine the degree of cytokine induction by the type 1 and type 3 Klebsiella fimbriae and their conjugates. Fimbriae were assessed as carrier proteins for Escherichia coli K12 endotoxin core oligosaccharide. MALDI-MS revealed the molecular mass of fimbrial monomer major protein, which was 15,847 Da for type 1 and 18,574 Da for type 3 fimbriae of Klebsiella. These two types of fimbriae were moderate inductors of IL-6 and interferon and almost inactive with regard to the stimulation of TNF when tested in human whole blood assay. Coupling of fimbriae with E. coli K12 core oligosaccharide gave immunogenic conjugates with respect to a saccharide ligand and protein carrier, although only 10% of the pilin monomers possessed the attached oligosaccharide. Rabbit antiserum reacted with a broad spectrum of lipopolysaccharides, as measured by ELISA and immunoblotting assays. The antibodies against glycoconjugates were bactericidal for the wild, S-type bacteria of some species. Regarding the induction of cytokines by conjugates only the TNF level was noticeably elevated. These results prompt for the practical use of fimbriae, as effective protein carriers for conjugates to obtain broad-spectrum antisera for diagnostic applications.

[Inhibition of peritoneal bacterial adhesion using oligosaccharides. An experimental model of peritonitis in rats]

BACKGROUND

Peritoneal colonization is a crucial event in the pathogenesis of peritonitis and its local complications. Adherence to the serosal mesothelium is mediated in a number of microorganisms derived from the digestive tract (especially E. coli) by type-1 fimbriae which have an oligosaccharide specificity.

PURPOSE

To evaluate the effect of repeated peritoneal washes with saline solution and oligosaccharides on E. coli peritoneal adherence in a rat peritonitis model.

METHODS

Sixty rats were randomized in 3 groups of 20. E. coli was inoculated at a constant concentration of 10(8)/mL per 100 g of weight. Then, peritoneal washes were achieved daily during three consecutive days (D1, D2, D3), with saline solution in Group I (control group), Methyl alpha-D-Mannoside (MADM) in Group II, and p-Nitro-phenyl alpha-D-Mannoside (pNADM) in Group III. Peritoneal samples were obtained before and after lavage at D1, D2, and D3. Microbial recovery was expressed as cfu/mg of tissue, and converted into a percentage of the initial value. A 10% threshold defined efficiency of the wash (inhibition of adherence for 90% of bacteries).

RESULTS

Compared with data from Group I, E. coli peritoneal adherence was significantly lower after washes in Group III (D1: p = 0.03; D2: p = 0.009; D3: p = 0.003). Repeated washes were more efficient in Group III than in Group II (D1: p = 0.1; D2: p = 0.5; D3: p = 0.001).

CONCLUSION

These results suggest that the addition of oligosaccharides, especially of pNADM, reduces the peritoneal adherence of E. coli when a peritoneal wash is performed for peritonitis.

Specificity of the high-mannose recognition site between Enterobacter cloacae pili adhesin and HT-29 cell membranes

Enterobacter cloacae has been implicated as one of the causative agents in neonatal infection and causes a septicemia thought to be initiated via the gastrointestinal tract. The adhesion of radiolabeled E. cloacae to HT-29 cells was concentration and temperature dependent and was effectively blocked by unlabeled bacteria or by millimolar concentrations of alpha-mannosides and micromolar concentrations of high-mannose oligosaccharides. A variety of well-characterized mannose oligosaccharides were tested as inhibitors of adhesion. The best inhibitor was the Man9(GlcNAc)2-tyrosinamide, which was considerably better than other tyrosinamide-linked oligosaccharides such as Man7(GlcNAc)2, Man6(GlcNAc)2 or Man5(GlcNAc)2. Further evidence that the bacteria preferred Man9(GlcNAc)2 structures was obtained by growing HT-29 cells in the presence of glycoprotein processing inhibitors that block mannosidase I and increase the amount of protein-bound Man9(GlcNAc)2 at the cell surface. Such cells bound 1.5- to 2-fold more bacteria than did control cells. The adhesin involved in binding to high-mannose structures was purified from isolated pili. On sodium dodecyl sulfate-gels, a 35-kDa protein was identified by its specific binding to a mannose-containing biotinylated albumin. The amino acid sequences of several peptides from the 35-kDa subunit showed over 85% identity to FimH, the mannose-specific adhesin of Salmonella typhimurium. Pili were labeled with 125I and examined for the ability to bind to HT-29 cells. Binding showed saturation kinetics and was inhibited by the addition of Man9(GlcNAc)2-tyrosinamide but not by oligosaccharides with fewer mannose residues. Polyclonal antibody against this 35-kDa protein also effectively blocked adhesion of pili or E. cloacae, but no effect was observed with nonspecific antibody. These studies demonstrate that the 35-kDa pilus subunit is a lectin whose specificity is directed toward Man, (GlcNAc)2 oligosaccharides.

Sulfur-binding protein of flagella of Thiobacillus ferrooxidans

The sulfur-binding protein of Thiobacillus ferrooxidans ATCC 23270 was investigated. The protein composition of the bacterium's cell surface changed according to the culture substrate. Sulfur-grown cells showed greater adhesion to sulfur than iron-grown cells. The sulfur-grown cells synthesized a 40-kDa surface protein which was not synthesized by iron-grown cells. The 40-kDa protein had thiol groups and strongly adhered to elemental sulfur powder. This adhesion was not disturbed by Triton X-100, which can quench hydrophobic interactions. However, adhesion was disturbed by 2-mercaptoethanol, which broke the disulfide bond. The thiol groups of the 40-kDa protein formed a disulfide bond with elemental sulfur and mediated the strong adhesion between T. ferrooxidans cells and elemental sulfur. The 40-kDa protein was located on the flagella. The location of the protein would make it possible for cells to be in closer contact with the surface of elemental sulfur powder.

Purification and characterization of type 1 fimbriae of Salmonella typhi

Type 1 fimbriae have been purified from a Salmonella typhi strain of clinical origin. Purified fimbriae retained their ability to bind to erythrocytes in a mannose-inhibitable fashion and, in doing so, behaved preferentially as a monovalent adhesin. SDS-PAGE analysis of the fimbrial preparation showed the presence of a 20-kDa major polypeptide component (fimbrillin) and of additional larger polypeptides present in smaller amounts. The amino-terminal sequence of fimbrillin was determined and turned out to be very similar but not identical to that of type 1 fimbrillins of other Salmonella serovars. A Western blot analysis of the purified fimbrial preparation using an antiserum raised against native fimbriae suggested that fimbrial proteins did not carry any major sequential epitope and that, in native fimbriae, conformational epitopes, possibly generated between different subunits, might provide for the major immunogenic epitopes. Analysis of different S. typhi clinical isolates using the anti-fimbrial antiserum showed an overall immunological similarity of these structures within this serovar.

Purification and N-terminal sequence of the alpha subunit of antigen 43, a unique protein complex associated with the outer membrane of Escherichia coli

Antigen 43 has been identified as a unique protein complex in the outer membrane of Escherichia coli. The complex contains two different polypeptides, alpha (Mr, 60,000) and beta (Mr, 53,000), in equal stoichiometry (P. Owen, P. Caffrey, and L.-G. Josefsson, J. Bacteriol. 169:3770-3777, 1987). The alpha subunit was released in a water-soluble form upon heating of outer membranes to 60 degrees C and was purified to apparent homogeneity by gel filtration and ion-exchange chromatography. The purified protein was acidic (pI 4.6) and had a polarity of 49.2%. The N-terminal sequence showed homology with the N termini of certain enterobacterial fimbrial subunits. In addition, antigen 43 underwent a reversible phase variation similar to that of type 1 fimbriae. By use of subunit-specific antisera, it was shown that the purified alpha subunit was capable of reassociating with the beta polypeptide. However, electron microscopic examination indicated that antigen 43 does not form a recognizable surface structure. The available evidence supports the view that antigen 43 is a complex consisting of a peripheral membrane protein (alpha) anchored to a subunit (beta) that is integral to the outer membrane.

Nucleotide sequences of the genes encoding type 1 fimbrial subunits of Klebsiella pneumoniae and Salmonella typhimurium

The nucleotide sequences of the genes encoding the subunits of Klebsiella pneumoniae and Salmonella typhimurium type 1 fimbriae were determined. Comparison of the predicted amino acid sequences of the two subunits revealed domains in which the sequences were highly conserved. Both gene products possessed signal peptides, a fact consistent with the transport of the fimbrial subunit across the membrane, but these regions showed no amino acid homology between the two proteins. The predicted N-terminal amino acid sequences of the processed fimbrial subunits were in good agreement with those obtained by purification of the fimbrial subunits.

Production of Pili (Fimbriae) by Pseudomonas fluorescens and Correlation with Attachment to Corn Roots

Pseudomonas fluorescens isolates 13525 and 2-79 were grown in Luria broth and low-nutrient medium (LNM). Pililike fibrils were very rarely produced in Luria broth but were abundantly produced in LNM. In LNM the pili were peritrichously distributed and had diameters ranging from 3 to 8 nm. Pili were purified from strain 2-79, and the pilin subunit was found to have a molecular weight of about 34,000. Strain 2-79 produced two colony types on Luria agar, nonmucoidal and mucoidal. Cells in LNM cultures of the nonmucoidal colony type were highly piliated, and cells from the mucoidal type were nearly devoid of pili. The presence of pili on nonmucoidal isolate 2-79 was quantitatively correlated with hydrophobic attachment to polystyrene, hemagglutination, and attachment to corn roots.

Opsonin independent interaction of Klebsiella strains with human polymorphonuclear leukocytes

Nine encapsulated Klebsiella strains with different types of fimbriation and their nonencapsulated mutants were tested for their stimulatory potency for human polymorphonuclear leukocytes in the absence of opsonins. The luminol chemiluminescence assay was used for these experiments. It could be shown that the interaction between Klebsiella bacteria and human leukocytes is rather complex depending not only on the presence of capsules but also on the hydrophobicity of Klebsiella surface and on the type of fimbriation existing.

Expression of pili from Bacteroides nodosus in Pseudomonas aeruginosa

The pili of Bacteroides nodosus, the causative agent of ovine footrot, constitute the major host-protective immunogen against homologous serotypic challenge. The pilin gene from B. nodosus 198 has been cloned and morphologically expressed as extracellular pili in Pseudomonas aeruginosa by using a plasmid-borne, thermoregulated expression system. B. nodosus pilin could not be detected in cultures of P. aeruginosa grown at 32 degrees C, but after induction at 37 degrees C, B. nodosus pili were expressed on the cell surface of P. aeruginosa to the virtual exclusion of the host cell pili. Pili harvested from induced P. aeruginosa cultures were used to immunize sheep against footrot. The serum agglutinating antibody titers of vaccinated sheep were comparable to those of sheep receiving pili from B. nodosus. Subsequent challenge of the sheep with B. nodosus 198 indicated that the recombinant- DNA-derived pili vaccine and the B. nodosus pili vaccine provided similar levels of protection against footrot.

Purification and characterization of fimbriae from Salmonella enteritidis

A human isolate of Salmonella enteritidis which displayed strong pellicle formation during static broth culture and mannose-sensitive hemagglutination produced fimbriae which were morphologically indistinguishable from type 1 fimbriae of members of the family Enterobacteriaceae. Fimbrin was purified to homogeneity, and the apparent molecular weight (Mr, 14,400) was markedly lower than that reported for the type 1 fimbrin of Salmonella typhimurium (Mr, 22,100). This fimbrin contained 40% hydrophobic amino acids and lacked cysteine. The sequence of the N-terminal 64 amino acids was determined, and sequence alignment revealed that although the 18 N-terminal residues of the S. enteritidis molecule shared considerable homology with Escherichia coli and S. typhimurium type 1 fimbrins, the S. enteritidis fimbrin lacked a 6- to 9-residue terminal sequence present in the other type 1 fimbrins and, after residue 18, shared little homology with the E. coli sequence. Antibodies raised to the purified S. enteritidis fimbrin bound to surface-exposed conformational epitopes on the native fimbriae and displayed pronounced serospecificity. These antibodies were used in the isolation of a nonfimbriated Tn10 insertion mutant which was unable to hemagglutinate.

Nucleotide sequence of the gene encoding the two-subunit pilin of Bacteroides nodosus 265

The nucleotide sequence of the gene encoding pilin from Bacteroides nodosus 265 has been determined. The pilin is encoded by a single-copy gene, from which can be predicted a prepilin comprising a single protein chain of Mr 16,637. The prepilin sequence differs in several respects from the mature protein sequence. Seven additional N-terminal amino acid residues are present in prepilin, whereas residue 8, phenylalanine, undergoes posttranslational modification to become the N-methylated amino-terminal residue of mature pilin. In addition, further processing occurs through internal cleavage to produce two noncovalently linked subunits characteristic of pilins from serogroup H of B. nodosus, of which strain 265 is a member. The position of cleavage has been identified between alanine residues at positions 72 and 73 of the mature 149-residue pilin protein. The predicted pilin sequence of B. nodosus 265 shows extensive N-terminal amino acid sequence homology with other pilins of the N-methylphenylalanine type. In addition this sequence also shows homology with these N-methylphenylalanine-type pilins in the C-terminal region of the molecule, especially with pilin from Pseudomonas aeruginosa PAK.

Role of Pili (Fimbriae) in Attachment of Bradyrhizobium japonicum to Soybean Roots

Pili (fimbriae) were observed on cells of each of the five strains of Bradyrhizobium japonicum and the one strain of Rhizobium trifolii examined. Pili on B. japonicum were about 4 nm in diameter and polarly expressed. Piliated cells were estimated by transmission electron microscopy and hydrophobic attachment to polystyrene to constitute only a small percentage of the total population. The proportion of piliated cells in these populations was dependent on culture age in some strains. Piliated B. japonicum cells were selectively and quantitatively removed from suspension when cultures were incubated with either soybean roots or hydrophobic plastic surfaces, indicating that pili were involved in the attachment of the bacteria to these surfaces. Pili from B. japonicum 110 ARS were purified and found to have a subunit molecular weight of approximately 21,000. Treatment of B. japonicum suspensions with antiserum against the isolated pili reduced attachment to soybean roots by about 90% and nodulation by about 80%. Pili appear to be important mediators of attachment of B. japonicum to soybean roots under the conditions examined.

A single-step isolation of K99 pili from B-44 strain of Escherichia coli

A single-step procedure has been developed to isolate pili from enterotoxigenic Escherichia coli strain B44 of calf origin. Pili, removed from the bacteria by heat shock treatment, were allowed to aggregate at 4 degrees C for 16 h. The precipitated pili, isolated by centrifugation, had typical pili morphology as shown by electron microscopy; ability to bind pig brush border; molecular weight greater than 6 million; and predominance of hydrophobic amino acids. On sodium dodecyl sulfate gel electrophoresis, the subunit pilin migrated as a single polypeptide of molecular weight 17,000.

Frequency among Enterobacteriaceae of the DNA sequences encoding type 1 pili

Type 1 pili, characterized by mannose-inhibitable agglutination of fowl or guinea pig erythrocytes, have been found throughout the family Enterobacteriaceae. A radiolabeled probe was prepared from a restriction endonuclease-digested fragment of the Escherichia coli pil operon and used to detect homologous DNA sequences in 236 bacteria representing 11 genera of Enterobacteriaceae. Only isolates identified as E. coli or Shigella spp. exhibited homology. In contrast, mannose-sensitive hemagglutination was observed in nine genera. Probe DNA did not hybridize to plasmid DNA, indicating a chromosomal location for the pil operon. Analysis of restriction nuclease-digested whole-cell DNA from 60 E. coli and two Shigella sp. isolates indicated that internal sequences were conserved in most strains, but that changes in flanking sequences in the chromosome were common.

Organization and expression of genes responsible for type 1 piliation in Escherichia coli

The genetic organization of a segment of recombinant DNA conferring the capacity of synthesize E. coli type 1 pili was examined. This 11.2-kilobase (kb) segment of DNA, derived from a clinical isolate, conferred a piliated phenotype (Pil+) on a nonpiliated (Pil-) strain of E. coli K-12 that lacked DNA homologous to the 11.2-kb region. Insertional mutagenesis, deletion mutagenesis, and subcloning of various regions of the 11.2-kb fragment allowed the localization of five genes, each encoding a polypeptide, that were associated with pilus expression. Three gene products, 17, 86, and 30 kilodaltons (kd) in size, were involved in pilus assembly; assembly of the 17-kd structural (pilin) protein into pili was not seen in mutants lacking either the 86- or 30-kd proteins, but pilin synthesis and proteolytic processing were not affected. The fourth polypeptide, 23 kd in size, appeared to be involved in the regulation of pilus expression because mutants lacking this protein exhibited a 40-fold increase in the amount of pilin antigen per cell. The last protein, 14 kd in size, was not associated with piliation by genetic criteria; however, the 14-kd protein was immunoprecipitated with pili, suggesting an association with pili or immunological cross-reactivity with pilin. Immunoprecipitates of minicell transcription translation products revealed that pilus polymerization was taking place in minicells. This may facilitate the study of the molecular steps in pilus biosynthesis and, as a consequence, provide clues to the assembly of supramolecular structures in general.

Progress in immunization against Klebsiella infections

Nosocomial infections with Klebsiella spp. are a leading cause of morbidity and mortality. The ability of Klebsiella spp. readily to colonize hospitalized patients, complications in treatment of infections due to R-factor-acquired antibiotic resistance, and the high mortality rate in certain patient populations, point to the need for immunoprophylactic/immunotherapeutic agents for disease control. The potential for vaccination against Klebsiella spp. is discussed in light of recent developments concerning the pathogenesis of Klebsiella infections as relates to the identification of protective antigens as possible vaccine candidates.

Type 3 fimbriae of Klebsiella sp.: molecular characterization and role in bacterial adhesion to plant roots

Type 3 fimbriae of Klebsiella were purified and characterized. The fimbriae were 4 to 5 nm in diameter and 0.5 to 2 microns long. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the fimbrillin had an apparent molecular weight of 23,500, and it differed from enterobacterial type 1 fimbrillins in its amino acid composition. Hydrophobic amino acids comprised 33.6% of all amino acids in the fimbrillin, which lacked cystine, phenylalanine, and arginine. Serologically, the type 3 fimbriae were also distinct from the type 1 fimbriae. Purified type 3 fimbriae agglutinated tannin-treated human blood group O erythrocytes; this confirms the role of type 3 fimbriae as hemagglutinins. Purified 125I-labeled type 3 fimbriae bound to the roots of Poa pratensis, and this binding could be inhibited by Fab fragments to the purified fimbriae. Anti-type 3 fimbriae Fab fragments also inhibited bacterial adhesion to plant roots. These results demonstrate that type 3 fimbriae mediate adhesion of klebsiellas to plant roots. Eight nitrogen-fixing strains of Klebsiella also produced type 3 fimbriae when grown under anaerobic nitrogen fixation conditions. It is proposed that type 3 fimbriae are involved in the establishment of the plant-bacterium association concerning nitrogen-fixing Klebsiella strains.

Isolation and characterization of F12 adhesive fimbrial antigen from uropathogenic Escherichia coli strains

The adhesive fimbrial antigen F12 from a strain of uropathogenic Escherichia coli has been isolated and characterized. The antigen was purified by ammonium sulfate precipitation and gel chromatography. The protein subunit of the F12 fimbria has a molecular weight of 18,200; the N-terminal amino acid sequence of the subunit shows close resemblance to that of the subunits of other F fimbriae and the type 1 fimbriae. We identified in these proteins a pattern of alternating conserved and variable amino acid residues which could indicate a special structural and functional feature.

Construction and expression of recombinant plasmids encoding type 1 fimbriae of a urinary Klebsiella pneumoniae isolate

The type 1 fimbriae of Klebsiella pneumoniae have been implicated as important virulence factors in mediating Klebsiella urinary infections. The chromosomally encoded fimbrial genes were cloned by a cosmid cloning technique. Further subcloning was performed with the cloning vehicles pBR322 and pACYC184, and a recombinant plasmid containing the fimbrial genes was constructed. After transformation by this plasmid, both Escherichia coli and Salmonella typhimurium were shown to express fimbriae which reacted with Klebsiella fimbrial antiserum. The approximate location of the relevant genes on the chimeric plasmid was determined by insertion of the transposable element Tn5. Hemagglutination-negative phenotypes were used to estimate the minimum size of the DNA fragment necessary to encode fimbrial biosynthesis and expression. The size of the coding region of this fragment was found to be 5.5 kilobase pairs.

Properties of pili from Escherichia coli SS142 that mediate mannose-resistant adhesion to mammalian cells

We isolated pili from Escherichia coli SS142. These pili had a diameter of 6 nm and an average length of 400 nm. They were composed of subunits with a molecular weight of 18,000. Their amino acid composition was determined; methionine and proline were not detected. The isolated pili retained mannose-resistant hemagglutinating activity. Proteolytic digestion and glutaraldehyde fixation led to partial or complete loss of the hemagglutinating activity of the pili without causing any detectable damage to their supramolecular structure, which was only disintegrated by treatment with hot sodium dodecyl sulfate. The hemagglutinating activity of E. coli SS142 was inhibited by the glycoproteins fetuin and Tamm-Horsfall protein, as well as by the glycolipids phytyl lactoside, dansyl-sphingosine lactoside, and digalactosyl diglyceride. Isolated pili inhibited the adhesion of the homologous strain E. coli SS142 to Intestine 407 cell monolayers, but did not inhibit the adhesion of E. coli strain B-413, B-506, or 2699. This indicates that E. coli SS142 binds to a receptor different from those recognized by the other strains and that mannose-resistant adhesion to tissue culture cells can be classified into different subtypes.

Immunoglobulin A and secretory immunoglobulin A antibodies to purified type 1 Klebsiella pneumoniae pili in human colostrum

Immunoglobulin A antibodies with binding specificity for purified Klebsiella pneumoniae type 1 pili were detected by an enzyme-linked immunosorbent assay in 20 of 21 human samples (95%). The concentrations of secretory immunoglobulin A antibody in colostrum directed against the pili were calculated by comparison of experimental enzyme-linked immunosorbent assay values with values obtained from known secretory immunoglobulin A concentrations. The presence of antibodies to K. pneumoniae type 1 pili was confirmed by double diffusion-gel studies with selected specimens of colostrum. This study shows that in the majority of human colostral samples examined, secretory immunoglobulin A antibodies with specificity for K. pneumoniae type 1 pili can be commonly found in variable, but frequently high, concentrations.

Proteinaceous bacterial adhesins and their receptors

The adhesion of bacteria to surfaces is an ecologically important property which enables them to colonize their natural habitats. Adhesion between bacteria mediated by sex pili and aggregation substances may also promote gene transfers. In this review, we describe the adhesive properties of bacteria (to eukaryotic and prokaryotic cells, and inert surfaces) and emphasize the characteristics of adhesins (structure, function, genetics, and morphology) and their cognate receptors on target surfaces. The physiochemical interactions between bacteria and surfaces can be described by the DLVO theory, but the interaction between bacterial adhesins and their receptor is better described as a ligand receptor interaction. The DLVO theory predicts that no physical contact can occur between bacteria and surface and, hence, predicts that adhesins must be filamentous in order to bridge the space between the two bodies and allow attachment of the bacteria. Adhesins are primarily proteinaceous, although adhesins of streptococci may involve dextrans or lipoteichoic acids. The cognate receptors for adhesins all appear to contain carbohydrates and as such as likely to be glycoconjugates with carbohydrate moieties acting as the receptor sites.