gingivalis strains in spreading. Whereas non-encapsulated strains are tackled directly by the immune system in localized abscesses, the more virulent encapsulated strains can evade this defence and cause phlegmonous infections [4–7]. Conclusions The epimerase-coding gene epsC of P. gingivalis is essential for CPS synthesis. The absence of CPS results in increased induction of IL-1β, IL-6 and IL-8 in human gingival fibroblasts upon in vitro infection with viable P. gingivalis cells. P. gingivalis CPS acts as a functional interface GM6001 in vivo between the pathogen and the host. The CPS-related reduced pro-inflammatory response can explain

why natural non-encapsulated strains cause localized abscesses and encapsulated strains spreading

phlegmonous infections. Methods Bacterial maintenance P. gingivalis strains were grown EPZ015938 molecular weight either on 5% horse blood agar plates (Oxoid no. 2, Basingstoke, UK) supplemented with hemin (5 μg/ml) and menadione (1 μg/ml) (BA+H/M plates) or BHI+H/M, both, at 37°C in an anaerobic atmosphere of 80% N2, 10% H2, and 10% CO2. Mutants were selected in the presence of 5 μg/ml erythromycin. Complemented mutants were selected in the presence of 50 μg/ml gentamycin and 1 μg/ml tetracycline. Purity of P. gingivalis liquid and plate-grown cultures was routinely checked by gram staining and microscopic examination. Escherichia coli DH5α was used for maintenance and construction of plasmids. CBL0137 datasheet DH5α was cultured in Luria-Bertani (LB) broth or on solid medium (LB broth with addition of 1.5% agar). Ampicillin (Na+ salt; 100 μg/ml) was added to the growth media to select for pUC-derived plasmids. E. coli S17-1 grown on LB supplemented with 5 μg/ml tetracycline carrying the complementation

construct pT-PG0120 was used for conjugation with P. gingivalis. Human gingival fibroblasts The gingival fibroblasts (HGF1 and HGF2) used in this study were collected from extracted third molars of two periodontally healthy subjects with a high pro-inflammatory immunological response when challenged with P. gingivalis [20]. Donors had given written informed consent, and the study was approved by the VUmc Medical Ethical committee. Genomic DNA isolation from P. gingivalis Genomic DNA from P. gingivalis strains was isolated from plate-grown bacteria using the DNeasy tissue kit (Qiagen Immune system Benelux BV). The DNA concentration of all samples after purification was between 20 ng/μl and 60 ng/μl. Generation of an insertional knockout construct for epsC To make an insertional knockout of epsC in the W83 wild type strain we constructed plasmid pΔEpsC. Primers epsC BamHI-F and epsC EcoRI-R (see table 1 for details) were used to amplify the 1.2 Kb epsC gene from P. gingivalis W83 genomic DNA in a PCR reaction. Pfu polymerase (Fermentas, GmbH, St. Leon-Rot, Germany) was used according to the manufacturer’s protocol with 100 ng of genomic DNA.