They

also suggested that the expression of hmuY mRNA in P. gingivalis cells grown in the same cell densities was similar regardless of the presence of heme. These results are different from those demonstrating higher hmuY mRNA expression levels in P. gingivalis cells grown under low-heme conditions and in biofilm, the latter resembling high-cell-density conditions [35–37]. Our results presented in this study corroborate the latter findings and demonstrate that HmuY protein is constitutively produced in the cell at low levels when bacteria are grown under high-iron/heme conditions; however, significantly higher protein levels are found in cells grown under low-iron/heme conditions, maintained in vitro by the addition of an iron chelator or human serum to the heme-free medium (figure 3). These experiments were performed using P. gingivalis cultures grown in the first selleck screening library passage of starvation, thus allowing achieving similar cell densities, especially in the early growth phase (data not shown). HmuY participates in homotypic MDV3100 mouse biofilm accumulation To cope with a changing environment and with continuous attacks of the host antimicrobial defense systems, bacteria produce a biofilm, which plays an important role in chronic infections due

to its ability to challenge the host immune system and resist antimicrobial treatment [39]. It has been demonstrated that P. gingivalis actively participates in biofilm formation [40], which facilitates learn more the long-term survival of the bacterium and induces an inflammatory reaction that is responsible for the destruction of the hard and soft tooth-supporting tissues. The transition from planktonic bacteria Org 27569 to biofilm-associated

cells involves changes in gene expression and is mediated at least in part by intercellular communication. A recent study demonstrated that HmuY is produced predominantly in P. gingivalis cells grown in biofilm compared with the cells growing in a planktonic form [35]. Biofilm formation begins with the production of an extracellular matrix, a structure that creates a shared space within the cellular community. In prokaryotes, the extracellular matrix is typically composed of carbohydrate polymers and proteins, and many of these proteins possess lipoprotein secretion signals. To determine if HmuY could be engaged in biofilm accumulation, we examined in vitro the homotypic biofilm-forming capabilities of wild-type (A7436, W83, and ATCC 33277) strains and a hmuY deletion mutant constructed in the A7436 strain (TO4). As shown in figure 5, bacteria grown under low-iron/heme conditions exhibited significantly greater biofilm accumulation than cells grown under high-iron/heme conditions. In addition, our data demonstrated that HmuY is involved in biofilm formation since P.