Evidence for the participation of N-acetylated amino sugars in the coaggregation between Cytophaga species strain DR2001 and Actinomyces israelii PK16

β-Glycyrrhetinic acid inhibits the bacterial growth and biofilm formation by supragingival plaque commensals

β-Glycyrrhetinic acid (BGA) is a natural antibacterial agent. Previous studies reported that BGA has antibacterial effects against several bacteria. This study evaluated the effects of BGA on the regulation of supragingival plaque bacteria. First, the minimum inhibitory concentrations (MICs) of BGA against oral bacteria were measured. Next, the minimum concentrations for inhibition of biofilm formation were evaluated against Streptococcus mutans and Streptococcus sobrinus, possessing insoluble glucan synthesis abilities. The MICs of biofilm formation by these bacteria ranged from 1/8 to 2× MIC. Furthermore, the inhibition effects of BGA against the coaggregation of Porphyromonas gingivalis and Streptococcus gordonii were evaluated. BGA at 32 or 64 μg/mL inhibited the coaggregation of these bacteria after a 30 min incubation. Lastly, the inhibition effects of BGA against human supragingival plaque bacteria were evaluated. Human supragingival plaque samples were obtained from 12 healthy donors. The inhibition effects of BGA against biofilm formation by these plaque bacteria were evaluated. Of 12 samples, the biofilm formation by 11 was significantly attenuated by 128-256 μg/mL of BGA. The number of colony forming units in these biofilms was also significantly attenuated. In conclusion, it was revealed that BGA inhibits the growth and biofilm formation of bacteria, furthermore, the same effect was confirmed with supragingival plaque bacteria. BGA is a good candidate for a natural agent that prevents the outbreak and progression of periodontal disease because it suppresses not only the growth and biofilm formation of bacteria, but also the coaggregation of P. gingivalis with plaque bacteria.

Probing of microbial biofilm communities for coadhesion partners

Investigations of interbacterial adhesion in dental plaque development are currently limited by the lack of a convenient assay to screen the multitude of species present in oral biofilms. To overcome this limitation, we developed a solid-phase fluorescence-based screening method to detect and identify coadhesive partner organisms in mixed-species biofilms. The applicability of this method was demonstrated using coaggregating strains of type 2 fimbrial adhesin-bearing actinomyces and receptor polysaccharide (RPS)-bearing streptococci. Specific adhesin/receptor-mediated coadhesion was detected by overlaying bacterial strains immobilized to a nitrocellulose membrane with a suspended, fluorescein-labeled bacterial partner strain. Coadhesion was comparable regardless of which cell type was labeled and which was immobilized. Formaldehyde treatment of bacteria, either in suspension or immobilized on nitrocellulose, abolished actinomyces type 2 fimbrial adhesin but not streptococcal RPS function, thereby providing a simple method for assigning complementary adhesins and glycan receptors to members of a coadhering pair. The method's broader applicability was shown by overlaying colony lifts of dental plaque biofilm cultures with fluorescein-labeled strains of type 2 fimbriated Actinomyces naeslundii or RPS-bearing Streptococcus oralis. Prominent coadhesion partners included not only streptococci and actinomyces, as expected, but also other bacteria not identified in previous coaggregation studies, such as adhesin- or receptor-bearing strains of Neisseria pharyngitis, Rothia dentocariosa, and Kingella oralis. The ability to comprehensively screen complex microbial communities for coadhesion partners of specific microorganisms opens a new approach in studies of dental plaque and other mixed-species biofilms.

Factors in virulence expression and their role in periodontal disease pathogenesis

The classic progression of the development of periodontitis with its associated formation of an inflammatory lesion is characterized by a highly reproducible microbiological progression of a Gram-positive microbiota to a highly pathogenic Gram-negative one. While this Gram-negative microbiota is estimated to consist of at least 300 different microbial species, it appears to consist of a very limited number of microbial species that are involved in the destruction of periodontal diseases. Among these "putative periodontopathic species" are members of the genera Porphyromonas, Bacteroides, Fusobacterium, Wolinella, Actinobacillus, Capnocytophaga, and Eikenella. While members of the genera Actinomyces and Streptococcus may not be directly involved in the microbial progression, these species do appear to be essential to the construction of the network of microbial species that comprise both the subgingival plaque matrix. The temporal fluctuation (emergence/disappearance) of members of this microbiota from the developing lesion appears to depend upon the physical interaction of the periodontal pocket inhabitants, as well as the utilization of the metabolic end-products of the respective species intimately involved in the disease progression. A concerted action of the end-products of prokaryotic metabolism and the destruction of host tissues through the action of a large number of excreted proteolytic enzymes from several of these periodontopathogens contribute directly to the periodontal disease process.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of adhesin-specific monoclonal antibodies to identify and localize an adhesin on the surface of Capnocytophaga gingivalis DR2001

Monoclonal antibodies capable of inhibiting coaggregation between Capnocytophaga gingivalis DR2001 and Actinomyces israelii PK16 were used to identify the adhesin on C. gingivalis that mediates the interaction. The monoclonal antibodies were used to demonstrate that a 140-kilodalton polypeptide found in the outer membrane of C. gingivalis was the adhesin responsible for coaggregation. A coaggregation-defective mutant that was unable to coaggregate with A. israelii lacked this large polypeptide. The monoclonal antibodies were also used to estimate the number of binding sites on the surfaces of individual cells and show how the adhesin molecules were arranged on the outer membrane. Values of between 220 and 280 were obtained for the number of adhesin molecules per cell. Immunoelectron microscopy performed with the monoclonal antibodies revealed that the adhesin molecules were arranged nonuniformly on the bacterial surface and occurred singly, in pairs, and in small clusters.

Utilization of a continuous streptococcal surface to measure interbacterial adherence in vitro and in vivo

Cell-to-cell interactions are essential for the formation of dental plaque. A continuous layer of Streptococcus sanguis SA-1 cells fixed to a solid surface has been used to evaluate interactions among this bacterium, Haemophilus parainfluenzae, and Streptococcus sobrinus. S. sanguis cells were attached to a Falcon 3001 tissue culture plates or bovine enamel chips, coated with a biological adhesive. Scanning electron microscopy of the chips showed the streptococci as a contiguous surface. Radiolabeled bacteria were used to measure a second-species interbacterial adherence to the streptococcal-coated culture plates. Strains of H. parainfluenzae known to coaggregate (strain HP-28) and not to coaggregate (strains HP-42 and HP-80), in suspension with S. sanguis strain SA-1, were studied for adherence. Ten-fold-higher numbers of coaggregating strain HP-28 adhered in vitro to the streptococcal layer than did the non-coaggregating strains. S. sobrinus strain 6715 did not show appreciable adherence to the S. sanguis surface. Saliva did not affect the adherence of coaggregating or non-coaggregating H. parainfluenzae strains to S. sanguis strain SA-1. Bovine enamel chips, coated with streptococci, mounted on modified orthodontic appliances and placed in the mouths of three volunteers, facilitated the measurement of interbacterial adherence in vivo of streptomycin-resistant strains of H. parainfluenzae (HP-28R or HP-42R). Suspensions of bacteria were placed into the mouth, distributed throughout, and expectorated. After 15 or 120 minutes, the appliance with the chips was removed, the chips sonified, and colony-forming units (CFU) of streptomycin-resistant haemophili determined per chip.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of lectinlike surface components on Capnocytophaga ochracea ATCC 33596 that mediate coaggregation with gram-positive oral bacteria

The interactions between Capnocytophaga ochracea ATCC 33596 and Streptococcus sanguis H1, Actinomyces naeslundii PK984, or Actinomyces israelii PK16 are dependent on specific recognitions between heat-sensitive adhesins on C. ochracea and heat-stable structures (probably carbohydrate-containing receptors) on the surfaces of these gram-positive coaggregation partners. The coaggregation of C. ochracea with each of these three organisms was inhibited by L-rhamnose and D-fucose and to a lesser extent by beta-methyl-galactoside. The reaction with S. sanguis was the most sensitive, while the coaggregation with A. israelii was the least sensitive and was only partially inhibited by each of the sugars that were considered to be effective inhibitors. A more effective inhibition of the coaggregation between C. ochracea and A. israelii was achieved by adding a combination of the 6-deoxysugars and N-acetylneuraminic acid. To further characterize the coaggregations, naturally occurring coaggregation-defective (Cog-) mutants of C. ochracea were obtained from several different selections. Three phenotypically distinct groups of mutants were were isolated. Type 1 mutants failed to coaggregate with S. sanguis only. Type 2 mutants lost ability to interact with both S. sanguis and A. naeslundii. Type 3 mutants failed to coaggregate with all three coaggregation partners. Characterization of the Cog- mutants by sugar inhibition studies made it possible to distinguish three classes of adhesin activity.

Multigeneric aggregations among oral bacteria: a network of independent cell-to-cell interactions

A radioactivity-based assay was developed to define the participation of radioactively labeled cell types within the milieu of unlabeled partners in multigeneric aggregates. The cell types in these multigeneric aggregations consisted of various combinations of 21 strains representing five genera of human oral bacteria. The coaggregation properties of each cell type, when paired individually with various strains, were delineated and were unchanged when the microbes took part in the more complex multigeneric aggregations. Competition between homologous labeled and unlabeled cells for binding to a partner cell type was achieved only when the homologous cells were mixed together before the addition of their partner cells. Attempts to displace a labeled cell type from an aggregate by subsequent addition of a large excess of the same unlabeled cell type were unsuccessful, which suggested that the forces that bound different cell types together were very strong and the cell-to-cell interactions were stable. However, a cell type that exhibited only lactose-reversible coaggregations with partners was easily and selectively released by the addition of lactose to multigeneric aggregates otherwise consisting solely of lactose-nonreversible cell-to-cell interactions. This not only indicates the independent nature of individual coaggregations but also suggests the involvement of lectinlike adhesins in these sugar-inhibitable coaggregations. Although the molecular mechanisms responsible for multigeneric aggregations are unknown, the principle of a common partner cell type serving as a bridge between two otherwise noncoaggregating cell types was firmly established by the observation of sequential addition of one cell type to another. Thus, competition, bridging, coaggregate stability, independent nature of interactions, and partner specificity are the key principles of adherence that form the framework for continued studies of multigeneric aggregates. While the human oral cavity is a prime example of a complex microbial community, collectively the community appears to consist of simple and testable individual interactions.

Identification and preliminary characterization of a lectinlike protein from Capnocytophaga gingivalis (emended)

A polypeptide believed to be the monomeric form of the lectin responsible for the coaggregation of Capnocytophaga gingivalis (emended) and Actinomyces israelii has been identified. Denaturing polyacrylamide gel electrophoresis and immunoblot analyses were used to distinguish the protein from other proteins in the outer membrane of C. gingivalis. The subunit of the putative lectin has a pI of 8.6 and a molecular weight of 155,000.

Coaggregation of oral Bacteroides species with other bacteria: central role in coaggregation bridges and competitions

Seventy-three freshly isolated oral strains representing 10 Bacteroides spp. were tested for their ability to coaggregate with other oral gram-negative and gram-positive bacteria. None coaggregated with any of the gram-negative strains tested, which included Capnocytophaga gingivalis, C. ochracea, C. sputigena, and Actinobacillus actinomycetemcomitans. Strains of Bacteroides buccae, B. melaninogenicus, B. oralis, and B. gingivalis failed to coaggregate with any of the gram-positive strains tested. However, six Bacteroides spp. coaggregated with one or more species of gram-positive bacteria. Most isolates of B. buccalis, B. denticola, B. intermedius, B. loescheii, B. oris, and B. veroralis coaggregated with strains of Actinomyces israelii, A. viscosus, A. naeslundii, A. odontolyticus, Rothia dentocariosa, or Streptococcus sanguis. The strongest coaggregations involved B. denticola, B. loescheii, or B. oris; 22 of 25 strains coaggregated with A. israelii. Only B. loescheii interacted with certain strains of S. sanguis; these coaggregations were lactose inhibitable and were like coaggregations between A. viscosus and the same strains of S. sanguis. In fact, B. loescheii and A. viscosus were competitors for binding to S. sanguis. Many bacteroides also acted as coaggregation bridges by mediating coaggregations between two noncoaggregating cell types (e.g., S. sanguis and A. israelii). Evidence for binding-site competition and coaggregation bridging involving noncoaggregating cell types from three different genera provides support for the hypothesis that these intergeneric cell-to-cell interactions have an active role in bacterial colonization of the oral cavity.