In contrast, all P. gingivalis cells grown in a planktonic form exhibited similar growth rates, suggesting that the mutation did not influence bacterial growth (see Additional file 3). All these data suggest that HmuY may play a significant role in biofilm accumulation on abiotic surfaces and support the importance of HmuY for P. gingivalis R788 in vitro survival during starvation, conditions similar to those found in plaque. Figure 5 Homotypic biofilm formation by P. gingivalis.

P. gingivalis wild-type (A7436, W83, and ATCC 33277) strains and the hmuY deletion mutant strain constructed in A7436 (TO4) were grown in basal medium supplemented with hemin (Hm) or dipyridyl (DIP). The microtiter plate biofilms were stained with crystal violet. Data are shown as the mean ± SD of three independent experiments (n = 24). Differences between the TO4 mutant and the wild-type A7436 strain expressed as p values are given above the respective bars. To facilitate adaptation to life within the oral cavity, P. gingivalis must be capable of sensing and responding to the prevailing environmental conditions, including nutrient availability, cell density,

and the presence of other bacteria. It has been recently shown that P. gingivalis possesses the luxS gene and produces a functional AI-2 autoinducer [41]. In P. gingivalis, among the many different bacterial features that are regulated by quorum sensing using LuxS ABT-888 clinical trial protein Clomifene is the expression of genes involved in iron and heme acquisition,

including the heme receptor HmuR [41, 42]. Although the authors analyzed hmuR gene expression only, it is highly possible that the expressions of other components of hmu operon, such as hmuY, may also be regulated by LuxS signaling. It has been shown that LuxS is also required in P. gingivalis for the development of biofilm under low-heme conditions [43], which additionally supports an involvement of HmuY in both heme uptake and biofilm accumulation. Anti-HmuY antibodies inhibit P. gingivalis growth and biofilm accumulation We further tested whether anti-HmuY antibodies had inhibitory activity against P. gingivalis, which was first determined by measuring the OD at 660 nm for planktonic bacteria after GSK2118436 research buy incubation of bacterial suspensions with pre-immune or immune anti-HmuY IgGs (figure 6). As shown in figure 7, incubation of P. gingivalis wild-type strains with immune anti-HmuY IgGs slightly decreased subsequent bacterial growth, especially in the early growth phase. The growth curves resemble those obtained for the hmuY-deficient strain. The lack of inhibition of bacterial growth in the late growth phase may be caused by the expression of other iron/heme uptake systems important for P. gingivalis at this growth stage. In contrast, anti-HmuY antibodies demonstrated a greater ability to reduce biofilm formation since P.