Project description:Here, we described a novel transcriptional regulator belonging to the MarR family that we named OsbR (oxidative stress response and biofilm formation regulator) in the opportunistic pathogen Chromobacterium violaceum. Transcriptome profiling by DNA microarray using strains with deletion or overexpression of osbR showed that OsbR exert a global regulatory role in C. violaceum, regulating genes involved in oxidative stress response, nitrate reduction, biofilm formation, and several metabolic pathways. EMSA assays showed that OsbR binds to the promoter regions of several OsbR-regulated genes and the in vitro DNA binding activity was inhibited by oxidants. We demonstrated that the overexpression of osbR caused activation of ohrA even in the presence of the repressor OhrR, which resulted in improved growth under organic hydroperoxide treatment. We showed that the proper regulation of the nar genes by OsbR ensures an optimal growth of C. violaceum under anaerobic conditions by tuning the reduction of nitrate to nitrite. Finally, the osbR overexpressing strain showed reduction in biofilm formation and this phenotype correlated with the OsbR-mediated repression of two gene clusters encoding putative adhesins.
Project description:A cDNA microarray was constructed from the expressed sequence tags (ESTs) of different developmental stages, and comparative genome hybridization based on microarray procedures were carried out. Dermatophyte species are classified into three genera: Epidermophyton, Microsporum, and Trichophyton. To determine the relationship between these three groups comparative genome hybridization were used in our experiment. Trichophyton rubrum genmic DNA was reference DNA and labelled by Cy3 while the other dermatophytes genomic DNA were test DNA and labelled by CY5. Test and reference DNA were co-hybridized with the T. rubrum cDNA microarray and the numbers of genes shared between each species and T. rubrum were determined. Keywords: Comparative Genomic Hybridization We used a Trichophyton rubrum cDNA microarray prepared in our lab through comparative genome hybridization of genomic DNA of 21 dermatophyte strains (belonging to 20 species) to elucidate the taxonomy and evolution profiles of 20 dermatophyte species. The numbers of genes shared between each species and T. rubrum were determined. Each strain DNA hybridized for 3 times. The slides were separated into three groups base on different datasets.