title: The rag locus of Porphyromonas gingivalis: a novel pathogenicity island.
abstract: Previous studies in our laboratories of the serum IgG antibody response of periodontal patients have demonstrated the presence of an immunodominant surface antigen (Mr 55 kDa) in the outer membrane of Porphyromonas gingivalis W50. Genetic analysis of this antigen revealed that the corresponding gene forms part of a small operon which may have arisen via horizontal gene transfer into the genome of this strain. On the basis of sequence homology, the 55 kDa antigen (RagB) and the product of a cotranscribed gene (RagA) may act in concert at the surface of the bacterium to facilitate active transport, mediated through the periplasmic spanning protein, TonB, or form part of a signal transduction system in this organism. The rag locus is present in only a proportion of P. gingivalis laboratory strains and clinical isolates. Analysis of the distribution of ragB in subgingival samples by PCR demonstrated that rag+ P. gingivalis are more frequently detected in deep periodontal pockets than shallow sites in periodontal patients. These findings indicate that the rag genes may influence the virulence potential of P. gingivalis strains which harbour this locus and may thus be considered a novel pathogenicity island. Furthermore, horizontal gene transfer between organisms in subgingival plaque may represent a significant force in the evolution of these bacteria with ramifications for both diagnosis and targeted treatment of periodontal disease.
authors.affiliation: Department of Oral Microbiology, St Bartholomew's and the Royal London School of Medicine and Dentistry, Queen Mary and Westfield College, UK. M.A.Curtis@mds.qmw.ac.uk
authors.forename: M A
authors.initials: MA
authors.lastname: Curtis
authors.forename: S A
authors.initials: SA
authors.lastname: Hanley
authors.forename: J
authors.initials: J
authors.lastname: Aduse-Opoku
mesh_terms: D000328:Adult; D000907:Antibodies, Bacterial / Q000097:blood; D000942:Antigens, Bacterial / Q000032:analysis; D000954:Antigens, Surface / Q000032:analysis; D001425:Bacterial Outer Membrane Proteins / Q000276:immunology; D001426:Bacterial Proteins / Q000502:physiology; D001693:Biological Transport, Active / Q000235:genetics; D002874:Chromosome Mapping; D003773:Dental Plaque / Q000382:microbiology; D022761:Gene Transfer, Horizontal; D005881:Gingiva / Q000382:microbiology; D006801:Humans; D016056:Immunodominant Epitopes / Q000032:analysis; D007074:Immunoglobulin G / Q000097:blood; D008565:Membrane Proteins / Q000502:physiology; D008875:Middle Aged; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics*; D009876:Operon / Q000235:genetics; D010510:Periodontal Diseases / Q000382:microbiology / Q000628:therapy; D010514:Periodontal Pocket / Q000382:microbiology; D016966:Porphyromonas gingivalis / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity*; D017385:Sequence Homology; D015398:Signal Transduction / Q000235:genetics; D014774:Virulence
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D016056:Immunodominant Epitopes; D007074:Immunoglobulin G; D008565:Membrane Proteins; C484343:RagA protein, Porphyromonas gingivalis; C484346:RagB protein, bacteria; C057616:tonB protein, Bacteria; D020559:Monomeric GTP-Binding Proteins