Identification of bistable populations of Porphyromonas gingivalis that differ in epithelial cell invasion.
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.
Suwannakul
S
S
Oral and Maxillofacial Pathology, School of Clinical Dentistry, The University of Sheffield, Sheffield S10 2TA, UK.
Stafford
G P
GP
Oral and Maxillofacial Pathology, School of Clinical Dentistry, The University of Sheffield, Sheffield S10 2TA, UK.
Whawell
S A
SA
Oral and Maxillofacial Pathology, School of Clinical Dentistry, The University of Sheffield, Sheffield S10 2TA, UK.
Douglas
C W I
CWI
Oral and Maxillofacial Pathology, School of Clinical Dentistry, The University of Sheffield, Sheffield S10 2TA, UK.
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
D018829:Adhesins, Bacterial; D000080867:Gingipain Cysteine Endopeptidases; D006861:Hydrogen Peroxide; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases