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H F Jenkinson

Publications and source records attributed to H F Jenkinson.

At least 19 recordsLinked to original sources
PubMed2003

From tooth to hoof: treponemes in tissue-destructive diseases.

With the advent of new molecular and immunological tools, there is better understanding of the roles that difficult to cultivate bacteria, and not-yet-cultivated bacteria such as spirochaetes, play in polymicrobial diseases. Only relatively recently have studies implicated Treponema spirochaetes in human periodontal disease, a destructive condition of the tissues supporting the teeth. A number of different Treponema species have been isolated and their surface protein components that mediate adhesion, cytotoxicity, and tissue damage have been characterized. More recently Treponema strains closely related to human oral isolates have been cultivated from active lesions of digital dermatitis, an ulcerative condition affecting the feet of cows and sheep. This condition, like periodontal disease, appears to have a polymicrobial aetiology in which enrichment for Treponema may play a crucial part. This article reviews the known mechanisms by which Treponema interact with eukaryotic host cells and tissue proteins, and how these interactions may contribute to pathogenic diversity.

Animals↗
PubMed2002

Invasion of dentinal tubules by oral bacteria.

Bacterial invasion of dentinal tubules commonly occurs when dentin is exposed following a breach in the integrity of the overlying enamel or cementum. Bacterial products diffuse through the dentinal tubule toward the pulp and evoke inflammatory changes in the pulpo-dentin complex. These may eliminate the bacterial insult and block the route of infection. Unchecked, invasion results in pulpitis and pulp necrosis, infection of the root canal system, and periapical disease. While several hundred bacterial species are known to inhabit the oral cavity, a relatively small and select group of bacteria is involved in the invasion of dentinal tubules and subsequent infection of the root canal space. Gram-positive organisms dominate the tubule microflora in both carious and non-carious dentin. The relatively high numbers of obligate anaerobes present-such as Eubacterium spp., Propionibacterium spp., Bifidobacterium spp., Peptostreptococcus micros, and Veillonella spp.-suggest that the environment favors growth of these bacteria. Gram-negative obligate anaerobic rods, e.g., Porphyromonas spp., are less frequently recovered. Streptococci are among the most commonly identified bacteria that invade dentin. Recent evidence suggests that streptococci may recognize components present within dentinal tubules, such as collagen type I, which stimulate bacterial adhesion and intra-tubular growth. Specific interactions of other oral bacteria with invading streptococci may then facilitate the invasion of dentin by select bacterial groupings. An understanding the mechanisms involved in dentinal tubule invasion by bacteria should allow for the development of new control strategies, such as inhibitory compounds incorporated into oral health care products or dental materials, which would assist in the practice of endodontics.

Animals↗
PubMed2001

The pavA gene of Streptococcus pneumoniae encodes a fibronectin-binding protein that is essential for virulence.

Streptococcus pneumoniae colonizes the nasopharynx in up to 40% of healthy subjects, and is a leading cause of middle ear infections (otitis media), meningitis and pneumonia. Pneumococci adhere to glycosidic receptors on epithelial cells and to immobilized fibronectin, but the bacterial adhesins mediating these reactions are largely uncharacterized. In this report we describe a novel pneumococcal protein PavA, which binds fibronectin and is associated with pneumococcal adhesion and virulence. The pavA gene, present in 64 independent isolates of S. pneumoniae tested, encodes a 551 amino acid residue polypeptide with 67% identical amino acid sequence to Fbp54 protein in Streptococcus pyogenes. PavA localized to the pneumococcal cell outer surface, as demonstrated by immunoelectron microscopy, despite lack of conventional secretory or cell-surface anchorage signals within the primary sequence. Full-length recombinant PavA polypeptide bound to immobilized human fibronectin in preference to fluid-phase fibronectin, in a heparin-sensitive interaction, and blocked binding of wild-type pneumococcal cells to fibronectin. However, a C-terminally truncated PavA' polypeptide (362 aa residues) failed to bind fibronectin or block pneumococcal cell adhesion. Expression of pavA in Enterococcus faecalis JH2-2 conferred > sixfold increased cell adhesion levels to fibronectin over control JH2-2 cells. Isogenic mutants of S. pneumoniae, either abrogated in PavA expression or producing a 42 kDa C-terminally truncated protein, showed up to 50% reduced binding to immobilized fibronectin. Inactivation of pavA had no effects on growth rate, cell morphology, cell-surface physico-chemical properties, production of pneumolysin, autolysin, or surface proteins PspA and PsaA. Isogenic pavA mutants of encapsulated S. pneumoniae D39 were approximately 104-fold attenuated in virulence in the mouse sepsis model. These results provide evidence that PavA fibronectin-binding protein plays a direct role in the pathogenesis of pneumococcal infections.

Adhesins, Bacterial↗
PubMed2001

Intra- and interspecies signaling between Streptococcus salivarius and Streptococcus pyogenes mediated by SalA and SalA1 lantibiotic peptides.

Streptococcus salivarius 20P3 produces a 22-amino-acid residue lantibiotic, designated salivaricin A (SalA), that inhibits the growth of a range of streptococci, including all strains of Streptococcus pyogenes. Lantibiotic production is associated with the sal genetic locus comprising salA, the lantibiotic structural gene; salBCTX genes encoding peptide modification and export machinery proteins; and salYKR genes encoding a putative immunity protein and two-component sensor-regulator system. Insertional inactivation of salB in S. salivarius 20P3 resulted in abrogation of SalA peptide production, of immunity to SalA, and of salA transcription. Addition of exogenous SalA peptide to salB mutant cultures induced dose-dependent expression of salA mRNA (0.2 kb), demonstrating that SalA production was normally autoregulated. Inactivation of salR encoding the response regulator of the SalKR two-component system led to reduced production of, and immunity to, SalA. The sal genetic locus was also present in S. pyogenes SF370 (M type 1), but because of a deletion across the salBCT genes, the corresponding lantibiotic peptide, designated SalA1, was not produced. However, in S. pyogenes T11 (M type 4) the sal locus gene complement was apparently complete, and active SalA1 peptide was synthesized. Exogenously added SalA1 peptide from S. pyogenes T11 induced salA1 transcription in S. pyogenes SF370 and in an isogenic S. pyogenes T11 salB mutant and salA transcription in S. salivarius 20P3 salB. Thus, SalA and SalA1 are examples of streptococcal lantibiotics whose production is autoregulated. These peptides act as intra- and interspecies signaling molecules, modulating lantibiotic production and possibly influencing streptococcal population ecology in the oral cavity.

Amino Acid Sequence↗
PubMed2000

Subgingival colonization by Porphyromonas gingivalis.

Porphyromonas gingivalis, a gram-negative anaerobe, is a major causative agent in the initiation and progression of severe forms of periodontal disease. In order to cause periodontal disease, P. gingivalis must colonize the subgingival region, a process that involves several distinct steps and multiple gene products. The organism must first navigate within the oral fluids in order to reach the hard or soft tissues of the mouth. Retention and growth of bacteria on these surfaces is facilitated by a repertoire of adhesins including fimbriae, hemagglutinins and proteinases. Once established subgingivally, P. gingivalis cells participate in intercellular communication networks with other oral prokaryotic cells and with eukaryotic cells. The establishment of these multiple interactive interfaces can lead to biofilm formation, invasion of root dentin and internalization within gingival epithelial cells. The resulting bacterial and host cellular locations, products and fate contribute to the success of P. gingivalis in colonizing the periodontal region.

Adhesins, Bacterial↗
PubMed2000

Expression of the virulence-related Sca (Mn2+) permease in Streptococcus gordonii is regulated by a diphtheria toxin metallorepressor-like protein ScaR.

The acquisition of transition metal ions by pathogenic bacteria is crucial to their growth and survival within the human host, however, the mechanisms of metal ion homeostasis in streptococci are unknown. The scaCBA operon in the human oral bacterium Streptococcus gordonii encodes the components of an ABC-type transporter for manganese (Mn2+). Production of substrate-binding lipoprotein ScaA was increased approximately fivefold in cells cultured in low Mn2+ medium (< 0.1 microM Mn2+), but not in iron (Fe2+/Fe3+)-limited medium, and was enhanced in the presence of human saliva or serum. mRNA analysis revealed that under low Mn2+ conditions, levels of scaCBA transcript (2.6 kb) were increased > 20-fold. The Mn2+-responsive transcriptional regulator of the sca operon was purified and characterized as a 215-amino-acid residue polypeptide, designated ScaR, with 26% identity to the Corynebacterium diphtheriae diphtheria toxin repressor (DtxR). Inactivation of scaR in S. gordonii DL1 (Challis) resulted in constitutive derepression of sca operon transcription. Expression of tpx, located immediately downstream of scaA and encoding a putative thiol peroxidase, was not subject to ScaR regulation. Purified ScaR protein bound to the scaC promoter region in vitro in the presence of Mn2+ (Kd approximately 80 nM) and, to a lesser extent, in the presence of Ni2+ or Zn2+. The metalloregulator protein binding region was localized by DNA protection analysis to a 46 bp sequence encompassing the -35 and -10 promoter signatures. This sequence was well conserved within the promoters of corresponding virulence-related permease operons in other streptococci. The results identify a new Mn2+-sensing regulator of Mn2+ transport in streptococci, important for Mn2+ homeostasis during infection of the human host.

Bacterial Adhesion↗
PubMed2000

Expression of green fluorescent protein in Streptococcus gordonii DL1 and its use as a species-specific marker in coadhesion with Streptococcus oralis 34 in saliva-conditioned biofilms in vitro.

Streptococcus gordonii is one of the predominant streptococci in the biofilm ecology of the oral cavity. It interacts with other bacteria through receptor-adhesin complexes formed between cognate molecules on the surfaces of the partner cells. To study the spatial organization of S. gordonii DL1 in oral biofilms, we used green fluorescent protein (GFP) as a species-specific marker to identify S. gordonii in a two-species in vitro oral biofilm flowcell system. To drive expression of gfp, we isolated and characterized an endogenous S. gordonii promoter, PhppA, which is situated upstream of the chromosomal hppA gene encoding an oligopeptide-binding lipoprotein. A chromosomal chloramphenicol acetyltransferase (cat) gene fusion with PhppA was constructed and used to demonstrate that PhppA was highly active throughout the growth of bacteria in batch culture. A promoterless 0.8-kb gfp ('gfp) cassette was PCR amplified from pBJ169 and subcloned to replace the cat cassette downstream of the S. gordonii-derived PhppA in pMH109-HPP, generating pMA1. Subsequently, the PhppA-'gfp cassette was PCR amplified from pMA1 and subcloned into pDL277 and pVA838 to generate the Escherichia coli-S. gordonii shuttle vectors pMA2 and pMA3, respectively. Each vector was transformed into S. gordonii DL1 aerobically to ensure GFP expression. Flow cytometric analyses of aerobically grown transformant cultures were performed over a 24-h period, and results showed that GFP could be successfully expressed in S. gordonii DL1 from PhppA and that S. gordonii DL1 transformed with the PhppA-'gfp fusion plasmid stably maintained the fluorescent phenotype. Fluorescent S. gordonii DL1 transformants were used to elucidate the spatial arrangement of S. gordonii DL1 alone in biofilms or with the coadhesion partner Streptococcus oralis 34 in two-species biofilms in a saliva-conditioned in vitro flowcell system. These results show for the first time that GFP expression in oral streptococci can be used as a species-specific marker in model oral biofilms.

Amino Acid Sequence↗
PubMed2000

Coinvasion of dentinal tubules by Porphyromonas gingivalis and Streptococcus gordonii depends upon binding specificity of streptococcal antigen I/II adhesin.

Cell wall-anchored polypeptides of the antigen I/II family are produced by many species of oral streptococci. These proteins mediate adhesion of streptococci to salivary glycoproteins and to other oral microorganisms and promote binding of cells to collagen type I and invasion of dentinal tubules. Since infections of the root canal system have a mixed anaerobic bacterial etiology, we investigated the hypothesis that coadhesion of anaerobic bacteria with streptococci may facilitate invasive endodontic disease. Porphyromonas gingivalis ATCC 33277 cells were able to invade dentinal tubules when cocultured with Streptococcus gordonii DL1 (Challis) but not when cocultured with Streptococcus mutans NG8. An isogenic noninvasive mutant of S. gordonii, with production of SspA and SspB (antigen I/II family) polypeptides abrogated, was deficient in binding to collagen and had a 40% reduced ability to support adhesion of P. gingivalis. Heterologous expression of the S. mutans SpaP (antigen I/II) protein in this mutant restored collagen binding and tubule invasion but not adhesion to P. gingivalis or the ability to promote P. gingivalis coinvasion of dentin. An isogenic afimbrial mutant of P. gingivalis had 50% reduced binding to S. gordonii cells but was unaffected in the ability to coinvade dentinal tubules with S. gordonii wild-type cells. Expression of the S. gordonii SspA or SspB polypeptide on the surface of Lactococcus lactis cells endowed these bacteria with the abilities to bind P. gingivalis, penetrate dentinal tubules, and promote P. gingivalis coinvasion of dentin. The results demonstrate that collagen-binding and P. gingivalis-binding properties of antigen I/II polypeptides are discrete functions. Specificity of antigen I/II polypeptide recognition accounts for the ability of P. gingivalis to coinvade dentinal tubules with S. gordonii but not with S. mutans. This provides evidence that the specificity of interbacterial coadhesion may influence directly the etiology of pulpal and periapical diseases.

Adhesins, Bacterial↗
PubMed1999

Influence of different functional elements of plasmid pGT232 on maintenance of recombinant plasmids in Lactobacillus reuteri populations in vitro and in vivo.

Plasmid pGT232 (5.1 kb), an indigenous plasmid of Lactobacillus reuteri 100-23, was determined, on the basis of nucleotide and deduced protein sequence data, to belong to the pC194-pUB110 family of plasmids that replicate via the rolling-circle mechanism. The minimal replicon of pGT232 was located on a 1.7-kb sequence consisting of a double-strand origin of replication and a gene encoding the replication initiation protein, repA. An erythromycin-selectable recombinant plasmid containing this minimal replicon was stably maintained (>97% erythromycin-resistant cells) without antibiotic selection in an L. reuteri population under laboratory growth conditions but was poorly maintained (<33% resistant cells) in the L. reuteri population inhabiting the murine gastrointestinal tract. Stable maintenance (>90% resistant cells) of pGT232-derived plasmids in the lactobacillus population in vivo required an additional 1.0-kb sequence which contained a putative single-strand replication origin (SSO). The SSO of pGT232 is believed to be novel and functions in an orientation-specific manner.

Amino Acid Sequence↗
PubMed1999

Cell wall-anchored CshA polypeptide (259 kilodaltons) in Streptococcus gordonii forms surface fibrils that confer hydrophobic and adhesive properties.

It has been shown previously that inactivation of the cshA gene, encoding a major cell surface polypeptide (259 kDa) in the oral bacterium Streptococcus gordonii, generates mutants that are markedly reduced in hydrophobicity, deficient in binding to oral Actinomyces species and to human fibronectin, and unable to colonize the oral cavities of mice. We now show further that surface fibrils 60.7 +/- 14.5 nm long, which are present on wild-type S. gordonii DL1 (Challis) cells, bind CshA-specific antibodies and are absent from the cell surfaces of cshA mutants. To more precisely determine the structural and functional properties of CshA, already inferred from insertional-mutagenesis experiments, we have cloned the entire cshA gene into the replicative plasmid pAM401 and expressed full-length CshA polypeptide on the cell surface of heterologous Enterococcus faecalis JH2-2. Enterococci expressing CshA exhibited a 30-fold increase in cell surface hydrophobicity over E. faecalis JH2-2 carrying the pAM401 vector alone and 2.4-fold-increased adhesion to human fibronectin. CshA expression in E. faecalis also promoted cell-cell aggregation and increased the ability of enterococci to bind Actinomyces naeslundii cells. Electron micrographs of negatively stained E. faecalis cells expressing CshA showed peritrichous surface fibrils 70.3 +/- 9.1 nm long that were absent from control E. faecalis JH2-2(pAM401) cells. The fibrils bound CshA-specific antibodies, as detected by immunoelectron microscopy, and the antibodies inhibited the adhesion of E. faecalis cells to fibronectin. The results demonstrate that the CshA polypeptide is the structural and functional component of S. gordonii adhesive fibrils, and they provide a molecular basis for past correlations of surface fibril production, cell surface hydrophobicity, and adhesion in species of oral "sanguis-like" streptococci.

Actinomyces↗
PubMed1999

The microbiology of periodontal disease.

Periodontal disease result from mixed bacterial infections, in which both host resistance barriers and bacterial interactions are important. Approximately ten bacterial species are strongly implicated with various forms of periodontal disease, although species that cannot yet be cultivated are likely also to be relevant. New technologies have shown that pathogenic bacterial species are present in defined complexes within subgingival plaque, thus identifying specific targets for therapeutic intervention. In light of increasing antibiotic resistance amongst oral bacteria, new strategies for control of periodontal bacterial complexes must be developed that inhibit the bacterial factors necessary for colonization and destruction of host tissues.

Aggregatibacter actinomycetemcomitans↗
PubMed1998

Binding properties of Streptococcus gordonii SspA and SspB (antigen I/II family) polypeptides expressed on the cell surface of Lactococcus lactis MG1363.

The oral bacterium Streptococcus gordonii expresses two cell wall-associated polypeptides, designated SspA (1,542 amino acid residues) and SspB (1,462 amino acid residues), that have 70% sequence identity. These polypeptides are members of the antigen I/II family of oral streptococcal adhesins and mediate the binding of streptococci to salivary glycoproteins, collagen, and other oral microorganisms such as Actinomyces naeslundii. To determine if SspA and SspB have differential binding properties, the coding sequences of the sspA and sspB genes were cloned into expression plasmid vector pTREX1-usp45LS to generate pTREX1-sspA and pTREX1-sspB, respectively, and the Ssp polypeptides were displayed on the cell surface of Lactococcus lactis MG1363. Lactococcal cells expressing similar levels of surface SspA or SspB polypeptide were then compared for their abilities to adhere to a range of antigen I/II polypeptide substrates. More than twice as many L. lactis cells expressing SspA bound to immobilized salivary agglutinin glycoprotein (SAG) as did L. lactis cells expressing SspB. In contrast, lactococci expressing SspB adhered twice as well as lactococci producing SspA to collagen type I and to Candida albicans. The binding of A. naeslundii to lactococci was only weakly enhanced by surface expression of Ssp polypeptides. L. lactis(pTREX1-sspB) cells bound in greater numbers to SAG than did Enterococcus faecalis JH2-2 cells expressing SspB from pAM401EB-5. The results suggest that SspA and SspB have markedly different binding affinities for their oral substrates and thus may function to promote site diversity in colonization by S. gordonii.

Adhesins, Bacterial↗
PubMed1998

The adhesion-associated sca operon in Streptococcus gordonii encodes an inducible high-affinity ABC transporter for Mn2+ uptake.

ScaA lipoprotein in Streptococcus gordonii is a member of the LraI family of homologous polypeptides found among streptococci, pneumococci, and enterococci. It is the product of the third gene within the scaCBA operon encoding the components of an ATP-binding cassette (ABC) transporter system. Inactivation of scaC (ATP-binding protein) or scaA (substrate-binding protein) genes resulted in both impaired growth of cells and > 70% inhibition of 54Mn2+ uptake in media containing < 0.5 microM Mn2+. In wild-type and scaC mutant cells, production of ScaA was induced at low concentrations of extracellular Mn2+ (< 0.5 microM) and by the addition of > or = 20 microM Zn2+. Sca permease-mediated uptake of 54Mn2+ was inhibited by Zn2+ but not by Ca2+, Mg2+, Fe2+, or Cu2+. Reduced uptake of 54Mn2+ by sca mutants and by wild-type cells in the presence of Zn2+ was abrogated by the uncoupler carbonylcyanide m-chlorophenylhydrazone, suggesting that Mn2+ uptake under these conditions was proton motive force dependent. The frequency of DNA-mediated transformation was reduced > 20-fold in sca mutants. The addition of 0.1 mM Mn2+ to the transformation medium restored only partly the transformability of mutant cells, implying an alternate role for Sca proteins in the transformation process. Cells of sca mutants were unaffected in other binding properties tested and were unaffected in sensitivity to oxidants. The results show that Sca permease is a high-affinity mechanism for the acquisition of Mn2+ and is essential for growth of streptococci under Mn2+-limiting conditions.

ATP-Binding Cassette Transporters↗
PubMed1998

Life below the gum line: pathogenic mechanisms of Porphyromonas gingivalis.

Porphyromonas gingivalis, a gram-negative anaerobe, is a major etiological agent in the initiation and progression of severe forms of periodontal disease. An opportunistic pathogen, P. gingivalis can also exist in commensal harmony with the host, with disease episodes ensuing from a shift in the ecological balance within the complex periodontal microenvironment. Colonization of the subgingival region is facilitated by the ability to adhere to available substrates such as adsorbed salivary molecules, matrix proteins, epithelial cells, and bacteria that are already established as a biofilm on tooth and epithelial surfaces. Binding to all of these substrates may be mediated by various regions of P. gingivalis fimbrillin, the structural subunit of the major fimbriae. P. gingivalis is an asaccharolytic organism, with a requirement for hemin (as a source of iron) and peptides for growth. At least three hemagglutinins and five proteinases are produced to satisfy these requirements. The hemagglutinin and proteinase genes contain extensive regions of highly conserved sequences, with posttranslational processing of proteinase gene products contributing to the formation of multimeric surface protein-adhesin complexes. Many of the virulence properties of P. gingivalis appear to be consequent to its adaptations to obtain hemin and peptides. Thus, hemagglutinins participate in adherence interactions with host cells, while proteinases contribute to inactivation of the effector molecules of the immune response and to tissue destruction. In addition to direct assault on the periodontal tissues, P. gingivalis can modulate eucaryotic cell signal transduction pathways, directing its uptake by gingival epithelial cells. Within this privileged site, P. gingivalis can replicate and impinge upon components of the innate host defense. Although a variety of surface molecules stimulate production of cytokines and other participants in the immune response, P. gingivalis may also undertake a stealth role whereby pivotal immune mediators are selectively inactivated. In keeping with its strict metabolic requirements, regulation of gene expression in P. gingivalis can be controlled at the transcriptional level. Finally, although periodontal disease is localized to the tissues surrounding the tooth, evidence is accumulating that infection with P. gingivalis may predispose to more serious systemic conditions such as cardiovascular disease and to delivery of preterm infants.

Animals↗
PubMed1997

Structure, function and immunogenicity of streptococcal antigen I/II polypeptides.

The antigen I/II family of cell-surface-anchored polypeptides in oral streptococci are structurally complex multi-functional adhesins, with multiple ligand-binding sites. Discrete regions within these polypeptides bind human salivary glycoproteins, other microbial cells, and calcium. Sequences within the N-terminal region bind preferentially fluid-phase glycoproteins, while the C-terminal half of the polypeptide contains species-specific adhesion-mediating sequences that bind surface-immobilized glycoproteins. These features may assist streptococcal adhesion to oral surface receptors despite the presence of excess fluid-phase receptors. Immunological studies reveal an array of T-cell and B-cell epitopes presented by antigen I/II polypeptides and suggest the occurrence of natural suppression of human antibodies to the adhesion-mediating sequences. The functional and immunological properties of antigen I/II proteins may account to a major extent for the success of oral streptococci colonizing and surviving within the human host.

Antigens, Bacterial↗
PubMed1997

Differential expression of type I cytokeratins in hamster cheek pouch epithelium following treatment with dimethylbenzanthracene.

Cytokeratin (CK) expression in untreated, paraffin-treated or dimethylbenzanthracene (DMBA)-treated hamster cheek pouch epithelium was investigated utilizing monoclonal antibodies AE1 or AE3, which react with type I or type II CKs, respectively, and by in situ hybridization utilizing type I CK-specific probes. The latter were isolated from a cDNA library of hamster cheek pouch mRNA and designated CK 13 and CK 10 based on their respective homologies (> 95% amino acids) with murine CK 13 and human CK 10. Treatment of hamster cheek pouch epithelium with DMBA resulted in increased expression of type I CK, detected immunohistochemically with monoclonal AE1, but decreased expression of type II CKs detected with AE3. Despite an overall increase in type I CKs, in situ hybridization demonstrated differential expression of type I CKs with altered distribution of CK 13 mRNA and reduced expression of CK 10 mRNA, providing additional sensitive markers for DMBA-associated changes in CKs. These changes were constant at 2 to 22 weeks in the pre-neoplastic and neoplastic epithelium following the initial application of DMBA.

9,10-Dimethyl-1,2-benzanthracene↗