The array data indicated that three putative sigma factors of the σ70 family PG0594 (rpoD), PG1660 and PG1827 were differentially regulated in biofilm cells. Both PG0594 and PG1660 were up-regulated whilst PG1827 was down-regulated in biofilm cells. The observed differential expression of these sigma factors in biofilm cells may indicate that these proteins are important regulators of P. gingivalis during biofilm growth. Genes encoding transport and binding proteins

Many genes predicted Semaxanib to encode transport and binding proteins were up-regulated in biofilm cells (Fig. 2). Six of these genes encode components of putative ABC transporter systems (PG0280, PG0281, PG1175, PG1663, PG2199 and PG2206). PG1175 and PG1663 are each predicted to be the inner membrane components Mizoribine price of an ABC transporter complex, each having an N-terminal https://www.selleckchem.com/products/BEZ235.html transmembrane domain and a C-terminal ABC ATPase domain. Interestingly, a RPSBLAST search based on the conserved domain database CDD [57] revealed that PG0280 and PG0281 encode putative permeases belonging to the family which includes LolC that has been shown to transport lipids across the inner membrane [58]. Potential virulence determinants and hypothetical genes The complete P. gingivalis genome sequence

has revealed a number of putative virulence determinants, several of which were highly up-regulated in biofilm cells. These include a putative sialidase (PG0352) and ADP-heptose-LPS heptosyltransferase (PG1155) with an average fold change of 3.22 and 2.58 respectively, a putative extracellular protease (PG0553) and thiol protease, tpr (PG1055) [59] with average fold changes of 6.22 and 12.28 respectively. We also observed an increased expression of the gene encoding HtrA, a putative periplasmic serine protease (htrA; PG0593) with an average fold change of 2.96. HtrA is known to play a role in biofilm formation of Streptococcus mutans [60] and virulence in a variety of bacterial species [61–63]. In P. gingivalis, HtrA has been shown to confer protection against oxidative stress and be involved in long term adaptation

to elevated temperature [64, 65]. HtrA has also been implicated in the modulation of the activity Bay 11-7085 of the gingipain cysteine proteinases at elevated temperature but it is not essential for the maturation or activation of the gingipains under normal conditions [64]. Interestingly htrA occurs in a predicted operon upstream of rpoD. In Salmonella enterica serovar Typhimurium [66, 67] and Yersinia enterocolitica [68, 69] an alternative sigma factor RpoE has been implicated in the regulation of htrA and resistance to oxidative stress. Taken together, these results suggest that perhaps HtrA in concert with RpoD may be part of a stress response that is activated during P. gingvalis biofilm growth. The majority of the differentially regulated P.