P. gingivalis é um dos principais patógenos da doença periodontal, é encontrado em biofilmes orais com S. gordonii e P. intermedia e em células endoteliais da artéria coronária in vivo. P. gingivalis necessita de ferro em seu metabolismo e pode usar certas proteínas do hospedeiro como fontes deste íon em ambientes limitantes. Assim, este estudo investigou o papel dos genes PGN0741/PG0637 (receptor dependente de TonB) e PGN0531/PG1380 (fvW) de P. gingivalis na formação de biofilme em diferentes concentrações de ferro, em biofilmes mistos com S. gordonii e P. intermedia, e na adesão e invasão de células endoteliais da artéria coronária. Os resultados mostraram divergências no papel dos genes TonB e fvW na formação dos monobiofilmes e mistos e em diferentes concentrações de ferro, demonstrando uma relação cepa-dependente. Na adesão, fvW se mostrou importante para ambas cepas, mas na persistência apenas para P. gingivalis W83. Este trabalho enfatiza, assim, a necessidade do uso de mais de uma cepa de P. gingivalis no estudo do papel de genes em ensaios experimentais. / P. gingivalis is one of the major pathogens of periodontal diseases. It is found in oral biofilms associated with S. gordonii and P. intermedia, and inside of coronary artery endothelial cells in vivo. P. gingivalis requires iron for growth and can exploit iron-carrying proteins of the host as sources in limiting environments. Thus, this work aimed to study the role of genes PGN0741/PG0637 (TonB-dependent receptor) and PGN0531/PG1380 (fvW) of P. gingivalis in biofilm formation under different iron concentrations, in mixed biofilms with S. gordonii and P. intermedia, and in the adhesion and invasion of coronary artery endothelial cells. Our data showed discordance for the role of TonB and fvW in homo- and heterotypic biofilm formation and in different iron concentrations. The relevance of both genes was strain-dependent. Gene fvW was relevant for adhesion to endothelial cells, but only for strain W83 during persistence. Therefore, our study emphasizes the importance of using different strains for a better understanding of the role of genes in experimental assays.

Dental plaque forms sequentially, with Fusobacterium nucleatum facilitating the adhesion of pathogenic late colonizers. We hypothesize that a single-chain variable fragment (scFv) antibody library will enable the identification of F. nucleatum adhesins and help elucidate the molecular mechanisms of coaggregation between F. nucleatum and other bacteria. A 4X10^8 clones scFv phage display library was created using spleen RNA from a mouse immunized with F. nucleatum. The library was enriched by biopanning against F. nucleatum 6 times and 292 individual clones tested by ELISA reacted strongly to F. nucleatum. Sixty-two of those clones inhibited F. nucleatum coaggregation with Streptococcus sanguinus. Analysis of select clones revealed differences in coaggregation inhibition, recognition of outer membrane proteins, and BstOI restriction pattern. DNA sequencing showed 6 unique scFvs and of them 3 strongly inhibited interaction with 5 Streptococcus species. These scFvs recognize the outer membrane autotransporter protein RadD (Fn1526), as determined by mass spectrometry. / Farhan Khan placed second in the International Association for Dental Research/Unilever Hatton Competition in the Senior Basic Science Research Category representing Canada, while presenting the research contained in this dissertation. This international competition took place during the 90th General Session & Exhibition of the International Association for Dental Research in Iguaçu Falls, Brazil in June 2012.

P. gingivalis é um dos principais patógenos da doença periodontal, é encontrado em biofilmes orais com S. gordonii e P. intermedia e em células endoteliais da artéria coronária in vivo. P. gingivalis necessita de ferro em seu metabolismo e pode usar certas proteínas do hospedeiro como fontes deste íon em ambientes limitantes. Assim, este estudo investigou o papel dos genes PGN0741/PG0637 (receptor dependente de TonB) e PGN0531/PG1380 (fvW) de P. gingivalis na formação de biofilme em diferentes concentrações de ferro, em biofilmes mistos com S. gordonii e P. intermedia, e na adesão e invasão de células endoteliais da artéria coronária. Os resultados mostraram divergências no papel dos genes TonB e fvW na formação dos monobiofilmes e mistos e em diferentes concentrações de ferro, demonstrando uma relação cepa-dependente. Na adesão, fvW se mostrou importante para ambas cepas, mas na persistência apenas para P. gingivalis W83. Este trabalho enfatiza, assim, a necessidade do uso de mais de uma cepa de P. gingivalis no estudo do papel de genes em ensaios experimentais. / P. gingivalis is one of the major pathogens of periodontal diseases. It is found in oral biofilms associated with S. gordonii and P. intermedia, and inside of coronary artery endothelial cells in vivo. P. gingivalis requires iron for growth and can exploit iron-carrying proteins of the host as sources in limiting environments. Thus, this work aimed to study the role of genes PGN0741/PG0637 (TonB-dependent receptor) and PGN0531/PG1380 (fvW) of P. gingivalis in biofilm formation under different iron concentrations, in mixed biofilms with S. gordonii and P. intermedia, and in the adhesion and invasion of coronary artery endothelial cells. Our data showed discordance for the role of TonB and fvW in homo- and heterotypic biofilm formation and in different iron concentrations. The relevance of both genes was strain-dependent. Gene fvW was relevant for adhesion to endothelial cells, but only for strain W83 during persistence. Therefore, our study emphasizes the importance of using different strains for a better understanding of the role of genes in experimental assays.