Extraction and properties of hemagglutinin from cell wall fragments of Fusobacterium nucleatum

Identification of a Fusobacterium nucleatum PK1594 galactose-binding adhesin which mediates coaggregation with periopathogenic bacteria and hemagglutination

Attachment of Fusobacterium nucleatum to various oral surfaces is mediated by several adhesins anchored on its outer surface. Monoclonal antibodies (MAbs) were prepared and used to identify the putative galactose-binding adhesin of F. nucleatum PK1594. Four unique MAbs, 8G7, 26B9, 28G11, and 29D4, were isolated on the basis of their ability to inhibit coaggregation of F. nucleatum PK1594 with Porphyromonas gingivalis PK1924. All four MAbs were also capable of inhibiting galactose-inhibitable interactions of F. nucleatum PK1594 with other oral gram-negative bacteria and with erythrocytes. Preincubation of F. nucleatum PK1594 with MAb 26B9 or its Fab fragments at concentrations lower than 1 microg/ml resulted in complete inhibition of coaggregation with P. gingivalis PK1924 or hemagglutination. F. nucleatum PK1594 surface components prepared by mild sonication or by extracting whole cells with detergents were subjected to Western blot analysis. None of the MAbs were able to recognize any polypeptide in these experiments. Therefore, detergent extracts of F. nucleatum PK1594 surface components were subjected to three experimental procedures: (i) separation by ion-exchange chromatography and testing of fractions for reaction with MAb 26B9 in an enzyme-linked immunosorbent assay (ELISA), (ii) lactose-Sepharose affinity chromatography and testing of the lactose eluate in ELISA with MAb 26B9, and (iii) immunoseparation with either MAb 26B9 or 8G7. Collectively, the results suggest that the putative adhesin is a 30-kDa outer membrane polypeptide which mediates the coaggregation with P. gingivalis PK1924 as well as other galactose-sensitive interactions of F. nucleatum PK1594.

Taxonomy, biology, and periodontal aspects of Fusobacterium nucleatum

The pathogenic potential of Fusobacterium nucleatum and its significance in the development of periodontal diseases, as well as in infections in other organs, have gained new interest for several reasons. First, this bacterium has the potential to be pathogenic because of its number and frequency in periodontal lesions, its production of tissue irritants, its synergism with other bacteria in mixed infections, and its ability to form aggregates with other suspected pathogens in periodontal disease and thus act as a bridge between early and late colonizers on the tooth surface. Second, of the microbial species that are statistically associated with periodontal disease, F. nucleatum is the most common in clinical infections of other body sites. Third, during the past few years, new techniques have made it possible to obtain more information about F. nucleatum on the genetic level, thereby also gaining better knowledge of the structure and functions of the outer membrane proteins (OMPs). OMPs are of great interest with respect to coaggregation, cell nutrition, and antibiotic susceptibility. This review covers what is known to date about F. nucleatum in general, such as taxonomy and biology, with special emphasis on its pathogenic potential. Its possible relationship to other periodontal bacteria in the development of periodontal diseases and the possible roles played by OMPs are considered.

Taxonomy, biology, and periodontal aspects of Fusobacterium nucleatum

The pathogenic potential of Fusobacterium nucleatum and its significance in the development of periodontal diseases, as well as in infections in other organs, have gained new interest for several reasons. First, this bacterium has the potential to be pathogenic because of its number and frequency in periodontal lesions, its production of tissue irritants, its synergism with other bacteria in mixed infections, and its ability to form aggregates with other suspected pathogens in periodontal disease and thus act as a bridge between early and late colonizers on the tooth surface. Second, of the microbial species that are statistically associated with periodontal disease, F. nucleatum is the most common in clinical infections of other body sites. Third, during the past few years, new techniques have made it possible to obtain more information about F. nucleatum on the genetic level, thereby also gaining better knowledge of the structure and functions of the outer membrane proteins (OMPs). OMPs are of great interest with respect to coaggregation, cell nutrition, and antibiotic susceptibility. This review covers what is known to date about F. nucleatum in general, such as taxonomy and biology, with special emphasis on its pathogenic potential. Its possible relationship to other periodontal bacteria in the development of periodontal diseases and the possible roles played by OMPs are considered.

Purification of arginine-sensitive hemagglutinin from Fusobacterium nucleatum and its role in coaggregation

Hemagglutinin of Fusobacterium nucleatum was extracted from Triton X-100-pronase P-treated cell envelopes, and was purified by affinity chromatography on L-arginine agarose. The hemagglutinin was inactivated by heating at 70 degrees C for 1 min. The activity was inhibited by L-arginine but was not affected by any sugars or by EDTA. The hemagglutinin aggregated 14 out of 17 strains of oral streptococci tested, and the bacterial aggregating activity was also inhibited by L-arginine. The results indicate the dominant role of this hemagglutinin in the adherence of this bacterium both to host cells and to other bacteria.

Three types of binding by Porphyromonas gingivalis and oral bacteria to fibronectin, buccal epithelial cells and erythrocytes

This study showed that the interaction of oral bacteria with fibronectin differed with the type of organism examined. Significant binding of fibronectin was found with Porphyromonas gingivalis non-fimbriated (F-) strain in comparison with the fimbriated strain (F+). However, the F+ strain adhered to buccal epithelial cells in significantly larger numbers than the F- strain. Fibronectin binding and epithelial cell adherence were not associated with haemagglutinating activity. These assays clearly define at least three distinct types of binding by oral bacteria: to fibronectin, buccal epithelial cells and erythrocytes.

A non-lectin-like mechanism by which Fusobacterium nucleatum 10953 adheres to and activates human lymphocytes

Most (approximately 80%) strains of Fusobacterium nucleatum adhere to human erythrocytes in a lectin-like manner that is strongly inhibited by N-acetyl-D-galactosamine (GalNAc). In this study, we investigated the capacity of F. nucleatum 10953, a strain that is weakly inhibited by GalNAc, to adhere to and activate human lymphocytes in vitro. Experiments using [3H]-labeled bacteria and scanning electron microscopy clearly showed that 10953 adhered to lymphocytes and that adherence was blocked by L-arginine+GalNAc greater than L-arginine much greater than GalNAc. Adherence was Ca(2+)-dependent, inhibited by pretreatment of the bacteria with proteases or heat, and unaffected by paraformaldehyde fixation of the bacteria. Strain 10953 induced lymphocyte mitogenesis that was blocked by L-arginine but not by GalNAc. These results suggest that certain strains of F. nucleatum, such as 10953, express a distinct, non-lectin-like mechanism by which they adhere to and activate lymphocytes. Activation of lymphocytes may be an important mechanism in the pathogenesis of periodontal diseases associated with these bacteria.

Adhesive properties of strains of Fusobacterium nucleatum of the subspecies nucleatum, vincentii and polymorphum

This study surveyed some adhesive properties of strains of Fusobacterium nucleatum representative of the 3 recently defined groups or subspecies that could relate to their colonization and virulence. With one exception, F. nucleatum strains agglutinated sheep erythrocytes, but the quantity of bacteria required and the sensitivity of the hemagglutination reactions to inhibition by 0.05 M galactose or arginine varied between strains, and did not exhibit clear-cut correlations with subspecies. Neuraminidase treatment of erythrocytes generally enhanced the hemagglutinating activity of most strains, but trypsin treatment had no effect. Strains of F. nucleatum also attached in moderate numbers to buccal epithelial cells. Treatment of the epithelial cells with neuraminidase or with trypsin increased the numbers of all Fusobacterium strains that attached. Treatment of hydroxyapatite (HA) beads with submandibular or parotid saliva also promoted the adhesion of all strains of F. nucleatum studied. Treatment of HA with human serum or albumin produced a selective effect. Adhesion of some strains was promoted by serum and albumin treatment, and that of other strains was unaffected. Adhesion of all strains of F. nucleatum was enhanced to statherin-treated HA, whereas HA treated with salivary proline-rich protein-1 did not foster F. nucleatum attachment. Three of 4 strains of the subspecies vincentii, and each of 2 polymorphum strains studied exhibited strong adhesion to HA treated with either human type I or type IV collagen. However, only 1 of 5 strains of the subspecies nucleatum bound well to collagen-treated HA.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of cryptic receptors (cryptitopes) in bacterial adhesion to oral surfaces

Progress in characterizing the receptors that promote bacterial attachment to teeth and oral epithelial cells has suggested that hidden molecular segments may frequently be involved. Such cryptic receptors, referred to as 'cryptitopes', may become exposed by several mechanisms. Hidden segments of salivary acidic proline-rich proteins evidently become exposed when the molecules undergo a conformational change as they adsorb to apatitic mineral. Adhesins of Actinomyces viscosus and certain other prominent dental plaque bacteria are able to bind to these cryptitopes, and this enables these organisms to bind to proline-rich proteins on apatitic surfaces while avoiding interactions with these proteins in solution. Cryptitopes may also become exposed as a result of enzymatic action. Thus, several bacteria, including Fusobacterium nucleatum, Eikenella corrodens, A. viscosus, A. naeslundii and Bacteroides intermedius, have adhesins that bind to galactosyl receptors which become exposed after treatment with neuraminidase. Similarly, the adhesion of some Gram-negative bacteria, such as Bact. gingivalis, is enhanced when tissue surfaces are treated with certain proteases, or lysosomal enzymes derived from human polymorphonuclear leucocytes. It seems likely that elevated levels of enzymes present in gingival fluid as sequelae of poor oral hygiene and gingivitis may generate cryptitopes for potentially periodontopathic bacteria, and thereby contribute to modulation of the gingival flora.

Surface properties and ultrastructure of Porphyromonas gingivalis W50 and pleiotropic mutants

Cell surface ultrastructure and other surface properties of Porphyromonas gingivalis strain W50 and pleiotropic mutants W50/BP1 (brown), and W50/BE1 (beige) were studied. The percentage hydrophobicity of strains W50, W50/BP1, W50/BR1, and W50/BE1 gradually decreased from 24 to 9. Ruthenium red stained cells studied by transmission electron microscopy revealed a layer of extracellular polymeric material of varying thickness depending on the strain. The layer was thickest in W50/BP1 (15-20 nm), strains W50 and W50/BR1 both had a layer of 12-15 nm, while strain W50/BE1 completely lacked this layer. The results clearly showed that the hydrophobicity of P. gingivalis was related not only to the thickness of the layer but also to other factors like the composition of the capsular material, such that only strain W50/BE1, for example, showed no haemagglutinating activity. The surface properties of the pleiotropic mutants appeared to be stable characteristics as cells grown on either solid or in liquid media gave comparable results. The loss of virulence of the beige strain (W50/BE1) is probably partly due to the alteration of these surface properties. Both virulent and avirulent strains, however, possessed extracellular vesicles.

Studies on the virulence properties and metabolism of pleiotropic mutants of Porphyromonas gingivalis (Bacteroides gingivalis) W50

Porphyromonas gingivalis (Bacteroides gingivalis) strain W50 and variants isolated from continuous culture designated W50/BP1 (black pigmented), W50/BR1 (brown pigmented) and W50/BE1 (beige or non-pigmented) were previously shown to lose virulence with the loss of pigmentation. Major properties which may affect the virulence and metabolism of P. gingivalis were compared amongst the 4 strains. The non-pigmented strain lost the ability to hemagglutinate sheep erythrocyte, had a reduced hydrophobicity and possessed lower levels of proteolytic activity. Defects in the electron transport system occurred at the level of cytochrome b but not menaquinone synthesis and resulted in an altered metabolic end product profile of the non-pigmented strain.

Partial characterization of a peptidoglycan-protein complex from Fusobacterium nucleatum Fev1

A protein in the cell wall of Fusobacterium nucleatum Fev1 remained associated with the peptidoglycan during extraction with various detergents and organic solvents. On digestion of this peptidoglycan-protein complex (PPC) with murein hydrolases, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed polypeptide bands with apparent molecular weights (MWs) in the range of 3000 to 40,000. After reaction with maleic anhydride the electrophoretic mobilities of these polypeptide bands increased to those of MWs 3000 to 12,000. The PPC protein showed a limited susceptibility toward trypsin, giving polypeptides that migrated in SDS-PAGE as a diffuse band with MW in the range of 3000 to 6000. The amino acid composition of all polypeptide bands eluted from SDS-PAGE was very similar, whichever enzyme was used for the solubilization of the PPC, and was nearly identical to that found for the protein moiety of the PPC. On the basis of a MW of 3000 for a protein unit, about one molecule of protein was found per five peptidoglycan subunits. Lanthionine was not found associated with released polypeptide, and muramic acid and glucosamine were either absent or present in amounts less than one molecule per protein unit. The PPC was immunogenic in rabbits, and purified anti-PPC IgG reacted with murein hydrolase-released protein separated on SDS-PAGE but preferentially with bands of MWs greater than 18,000.

Purification and properties of hemagglutinin from culture supernatant of Bacteroides gingivalis

The hemagglutinating factor (hemagglutinin) of Bacteroides gingivalis was prepared from the supernatant of a 5-day diffusate broth culture by ammonium sulfate precipitation and column chromatography with a hydrophobic column of Phenyl-Sepharose CL-4B, DEAE-Sephadex A-50, and Sephadex G-100 gel filtration. The hemagglutinating activity of the preparation was 53.3 times higher than that of ammonium sulfate precipitate. In electron microphotographs, hemagglutinin appears to have a vesicle or tubelike structure. The hemagglutinating activity of intact cells was completely destroyed by heating at 100 degrees C for 10 min, but the activity of extracted hemagglutinin was heat stable. The activity of hemagglutinin was inhibited by L-arginine and L-lysine and partially inhibited by phospholipase D, but it was not affected by proteolytic enzymes, neuraminidase, hyaluronidase, lipase, phospholipase A and C, or sugars. The B. gingivalis hemagglutinin appeared to be comprised mainly of a 40,000-molecular-weight material. The Fab fragment of immunoglobulin G prepared from rabbit antiserum to whole cells of B. gingivalis and monoclonal antibody against the hemagglutinin bound to the cell surface and inhibited the hemagglutinating activity of both the cells and the purified hemagglutinin.

Isolation and some properties of exohemagglutinin from the culture medium of Bacteroides gingivalis 381

Exohemagglutinin was found in the culture medium of Bacteroides gingivalis 381. Exohemagglutinin was purified 3,150-fold from culture fluid by ultracentrifugation followed by gel filtration on Sepharose CL-4B and by affinity chromatography on arginine-agarose. Examination of the final preparation of exohemagglutinin by biochemical analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the isolated exohemagglutinin contained three major proteins but not a detectable lipopolysaccharide. Hemagglutination inhibition experiments showed that the activity of exohemagglutinin was inhibited by L-arginine and the arginine-containing peptides, although the activity was unaffected by the sugars tested. Some protein and glycoproteins that were examined also exhibited the inhibitory activity. When the bovine submaxillary mucin was chemically modified by beta-elimination and bovine serum albumin was modified by guanidination, the inhibitory effects on hemagglutination were significantly enhanced. These results suggest that the hemagglutination of the isolated exohemagglutinin may be involved in arginine residues as components of ligand-binding sites on erythrocytes.