2, red circles and Additional File 5, Table S5). Of these 82 statistically significant altered transcripts, only 4 were commonly altered with the same magnitude by a deletion of vjbR or wildtype cells treated with C12-HSL (Fig. 2). At the exponential growth phase, administration of C12-HSL exerted an equal effect on gene expression, up and down-regulating

19 and find more 23 genes (respectively, Fig. 2). On the contrary, at the stationary phase all 48 genes were up-regulated, a dramatically different profile than the down-regulation observed for the majority of differently expressed genes in C12-HSL treated wildtype cells (Fig. 2). Collectively, this data supports that C12-HSL is capable of influencing gene expression independent of VjbR. There is evidence that C12-HSL may interact with a second LuxR homologue, BlxR [18]. Induction of blxR expression in response to C12-HSL was highly variable by microarray analysis; however, qRT-PCR revealed that blxR was up-regulated 99.5-fold in bacteria lacking HSP inhibitor drugs vjbR treated with C12-HSL, compared to 27.5-fold in wildtype cells that were administered C12-HSL at the stationary growth phase. One possible explanation for this observation is that VjbR inhibits the induction of blxR by binding the AHL substrate and therefore

lowering the cellular concentration of available C12-HSL for blxR induction, but has not been demonstrated. Interestingly, 58% of the gene transcripts found to be altered in an recent study of the function of ΔblxR were also found to be altered by the addition of C12-HSL in the ΔvjbR background, and increased to 88% if we lowered the threshold from our 1.5-fold cutoff (Additional File 5, Table S5) [15]. A second study that similarly examined the transcript and proteomic alterations due to a deletion in babR corresponded with 6 genes identified in our study: with 2 genes found to be unique to the addition of C12-HSL in the ΔvjbR background (BMEI0231 and I1638, Additional File 5, Table S5), and 4 genes additionally altered by the deletion of vjbR or addition

of C12-HSL in the wildtype background (BMEI0451, I0712, I1196 and II0358, Additional File 3, Table S3) [23]. Although Cyclin-dependent kinase 3 many of these genes were not statistically significant in our analyses, this is a strikingly high correlation since the same conditions were not examined (ΔblxR vs. wt compared to ΔvjbR vs. ΔvjbR + C12-HSL), as well as the use of differing microarray platforms and analyses procedures. This connection may suggest that the genes altered by the presence of C12-HSL in the absence of VjbR may be due to C12-HSL activation of BlxR. Conclusions The goal of this work was to provide an elementary understanding in the role of the putative QS components in the virulence and survival of B. melitensis.