Project description:Histone-like nucleoid structuring (H-NS) proteins silence horizontally-acquired genes, facilitating their the acquisition and integration of important traits such as virulence and antibiotic resistance in bacterial pathogens. In this work, we describe the H-NS proteins in the environmental opportunistic pathogen Chromobacterium violaceum. We show that C. violaceum encodes two H-NS proteins, Chn1 and Chn2. Transcriptomic analyses revealed that Chn1 is the predominant H-NS-family protein in C. violaceum, repressing many genes, while Chn2 is largely compensatory, exhibiting a phenotype only in a double mutant, chn1 chn2 strain. This is reinforced by in silico analyses showing that chn1 is conserved throughout Chromobacterium, while chn2 is species-dependent, and likely horizontally-acquired. The expression of 213 genes, including the Chromobacterium pathogenic island 2 (Cpi-2), was de-repressed in the chn1 chn2 mutant. Phenotypic analyses revealed altered virulence, violacein production, motility and acid and osmolarity tolerance in chn1 and chn1 chn2 mutant strains, demonstrating the prominent role of these H-NS-family proteins as global regulators of virulence-associated traits in C. violaceum.
Project description:Violacein, an indole-derived purple-colored natural pigment isolated from Chromobacterium violaceum has shown multiple biological activities. In this study, we report that violacein activates murine macrophages through the up-regulation of TNF-α expression at non-cytotoxic concentrations (2 µmol/L). This was evaluated by measurement of TNF-α expression using real-time qRT-PCR. In addition, we obtained evidence of the molecular mechanism of activation by determining the mRNA expression pattern upon treatment with violacein. Interestingly, the mRNA expression pattern also allowed us to observe that incubation with violacein caused activation of pathways related with an immune and inflammatory response. Together, our data indicate that violacein activates the TLR8 receptor signaling pathway, and in consequence induces production of inflammatory cytokines such as TNF-α, CCL3 and CCL4 and of negative regulators of TLR signaling such as AP20, IRG1, IκBα and IκBε. Finally, we studied the interaction of TLR8 with violacein in silico, and obtained evidence that violacein could bind to TLR8 in a similar fashion to imidazoquinoline compounds. Therefore, our results indicate that violacein could be a candidate to be applied in immune therapy.
Project description:Frequency-dependent response of Chromobacterium violaceum to sonic stimulation, and altered gene expression associated with enhanced violacein production at 300 Hz
