title: Identification of bistable populations of Porphyromonas gingivalis that differ in epithelial cell invasion.
abstract: Bistable populations of bacteria give rise to two or more subtypes that exhibit different phenotypes. We have explored whether the periodontal pathogen Porphyromonas gingivalis exhibits bistable invasive phenotypes. Using a modified cell invasion assay, we show for the first time that there are two distinct subtypes within a population of P. gingivalis strains NCTC 11834 and W50 that display differences in their ability to invade oral epithelial cells. The highly invasive subtype invades cells at 10-30-fold higher levels than the poorly invasive subtype and remains highly invasive for approximately 12-16 generations. Analysis of the gingipain activity of these subtypes revealed that the highly invasive type had reduced cell-associated arginine-specific protease activity. The role of Arg-gingipain activity in invasion was verified by enhancement of invasion by rgpAB mutations and by inclusion of an Arg-gingipain inhibitor in invasion assays using wild-type bacteria. In addition, a population of ΔrgpAB bacteria did not contain a hyperinvasive subtype. Screening of the protease activity of wild-type populations of both strains identified high and low protease subtypes which also showed a corresponding reduction or enhancement, respectively, of invasive capabilities. Microarray analysis of these bistable populations revealed a putative signature set of genes that includes oxidative stress resistance and iron transport genes, and which might be critical to invasion of or survival within epithelial cells.
authors.affiliation: Oral and Maxillofacial Pathology, School of Clinical Dentistry, The University of Sheffield, Sheffield S10 2TA, UK.
authors.forename: S
authors.initials: S
authors.lastname: Suwannakul
authors.affiliation: Oral and Maxillofacial Pathology, School of Clinical Dentistry, The University of Sheffield, Sheffield S10 2TA, UK.
authors.forename: G P
authors.initials: GP
authors.lastname: Stafford
authors.affiliation: Oral and Maxillofacial Pathology, School of Clinical Dentistry, The University of Sheffield, Sheffield S10 2TA, UK.
authors.forename: S A
authors.initials: SA
authors.lastname: Whawell
authors.affiliation: Oral and Maxillofacial Pathology, School of Clinical Dentistry, The University of Sheffield, Sheffield S10 2TA, UK.
authors.forename: C W I
authors.initials: CWI
authors.lastname: Douglas
mesh_terms: D018829:Adhesins, Bacterial / Q000378:metabolism*; D016866:Bacteroidaceae Infections / Q000382:microbiology*; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004847:Epithelial Cells / Q000382:microbiology*; D020869:Gene Expression Profiling; D000080867:Gingipain Cysteine Endopeptidases; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D018384:Oxidative Stress; D010447:Peptide Hydrolases / Q000378:metabolism; D010641:Phenotype; D016966:Porphyromonas gingivalis / Q000201:enzymology / Q000235:genetics / Q000472:pathogenicity*; D014774:Virulence
chemical_list: D018829:Adhesins, Bacterial; D000080867:Gingipain Cysteine Endopeptidases; D006861:Hydrogen Peroxide; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases