cenocepacia. In addition, we have investigated the molecular mechanisms with which BDSF signaling system influencing AHL signal production and unveiled the involvement of the second messenger c-di-GMP. Furthermore, we have determined the relationships of these two QS systems in the cell-cell communication signaling cascade and their

impacts on bacterial physiology and virulence. Results BDSF system positively regulates AHL signal production To further confirm whether the AHL and BDSF systems are functionally related, we determined Trichostatin A price the AHL and BDSF signal production levels in corresponding mutants. Consistently, we found deletion of either the AHL synthase gene cepI or the AHL receptor gene cepR had no effect on BDSF production (data no www.selleckchem.com/products/Vincristine-Sulfate.html shown). However, we found that disruption of the BDSF synthase gene rpfF Bc in B. cenocepacia H111 caused a significant reduction of the total AHL signal level with the aid of AHL reporter strain (Figure 1A). BDSF production was restored by in trans expression of the wild type rpfF Bc (Figure 1A), confirming the role of BDSF system in regulation of AHL biosynthesis. In contrast, in trans expression of rpfF Bc in the cepI deletion mutant displayed no effect, suggesting that BDSF probably functions through

modulation of CepI expression level or enzyme activity. Furthermore, we used the TLC method to analyze the different AHL signals produced by these strains. Results showed that deletion of rpfF Bc affected the production of both HHL and OHL signals in B. cenocepacia H111 (Figure 1B). Figure 1 Influence of the BDSF system on AHL signal production. (A) AHL signal

production was quantified with the aid of AHL reporter strain CF11 to test the β-galactosidase activity. (B) TLC assay of AHL signal production. For convenient comparison, the AHL signal production of wild-type strain was defined as 100% and used to normalize the AHL signal production of other strains. The data presented are the means of three replicates and error bars represents the standard deviation. BDSF system positively controls cepI expression at transcriptional level To further study the regulation mechanism of the BDSF system on AHL Thalidomide signal production, we constructed the cepI reporter system in B. cenocepacia H111 strains to test whether BDSF system controls cepI expression at transcriptional level. In agreement with the above results, deletion of rpfF Bc resulted in a reduced expression of cepI at various growth stages (Figure 2A). Exogenous addition of BDSF rescued the cepI expression in ΔrpfFBc close to the wild-type level (Figure 2A). In agreement with the above results, western blotting analysis showed that null mutation of RpfFBc substantially decreased the CepI protein level (Figure 2B).