Project description:Gene expression in the obligatory aerobic acetic acid bacterium Gluconobacter oxydans was shown to respond to oxygen limitation, but the regulators involved are unknown. In this study, we analyzed the function of a transcriptional regulator named GoxR, which belongs to the FNR family. Here, we applied ChAP-seq analysis with a strep-tagged GoxR version to identify binding sites of this regulator in the genome of G. oxydans.
Project description:Toxic inhibitory compounds from lignocellulose pretreatment are the major obstacle to achieve high bioconversion efficiency in biorefinery fermentations. This study shows a unique glucose oxidation catalysis of Gluconobacter oxydans with its gluconic acid productivity free of inhibitor disturbance. The microbial experimentations and the transcriptome analysis revealed that both the activity of the membrane-bound glucose dehydrogenase (mGDH) and the transcription level of the genes in periplasmic glucose oxidation respiratory chain of G. oxydans were essentially not affected under the existence of inhibitory compounds. G. oxydans also rapidly converted furan and phenolic aldehyde inhibitors into the less toxic alcohols or acids. The synergy of the robust periplasmic glucose oxidation and the rapid inhibitor conversion of G. oxydans significantly elevated the efficiency of the oxidative fermentation in lignocellulose hydrolysate. The corresponding genes responsible for the conversion of furan and phenolic aldehyde inhibitors were also mined by DNA microarrays. The synergistic mechanism of G. oxydans provided an important option of metabolic modification for enhancing inhibitor tolerance of general fermentation strains.
Project description:Gene expression in the obligatory aerobic acetic acid bacterium Gluconobacter oxydans was shown to respond to oxygen limitation, but the regulators involved are unknown. In this study, we analyzed the function of a transcriptional regulator named GoxR, which belongs to the FNR family. Here, we aplied RNAseq to identify target genes of GoxR by comparing genes expression of a delta-goxR and its parental strain after 20 min of oxygen limitation.
Project description:The genome-wide transcriptional responses of the strictly aerobic -proteobacterium Gluconobacter oxydans 621H to oxygen limitation, to the absence of the cytochrome bc1 complex, and to low pH were studied using DNA microarray analyses. Oxygen limitation caused expression changes of 486 genes, representing 20% of the chromosomal genes. Genes with an increased mRNA level included those for terminal oxidases, the cytochrome bc1 complex, transhydrogenase, two alcohol dehydrogenases, heme biosynthesis, PTS proteins, proteins involved in cyclic diGMP synthesis and degradation, two sigma factors, flagella and chemotaxis proteins, several stress proteins, and a putative exporter protein. The downregulated genes comprised those for respiratory dehydrogenases, enzymes of central metabolism, PQQ biosynthesis, outer membrane receptors, Sec proteins, and proteins involved in transcription and translation. A M-NM-^TqrcABC mutant of G. oxydans showed a growth defect during cultivation on mannitol at pH 4 under oxygen saturation. Comparison of the transcriptomes of this mutant versus the wild type under these conditions revealed 51 differentially expressed genes. Interestingly, almost all of the 45 genes with increased expression in the M-NM-^TqrcABC mutant at pH 4 were also upregulated in the wild type grown at pH 6 under oxygen limitation. These results support an active role of the cytochrome bc1 complex in G. oxydans respiration. The transcriptome comparison of G. oxydans wild type at pH 4 versus pH 6 in mannitol medium under oxygen-saturated conditions uncovered only 72 differentially expressed genes. The 35 upregulated genes included those for cytochrome bd oxidase, major polyol dehydrogenase, iron storage and oxidative stress proteins. Among the 37 downregulated genes were some encoding enzymes dealing with carbon dioxide, such as biotin carboxylase, biotin carboxyl carrier protein, and carboanhydrase. These results give first insights into global transcriptional responses of G. oxydans. DNA microarray experiments were repeated independently three times for G. oxydans M-NM-^TqrcABC versus wild type and G. oxydans grown at pH 4 versus pH 6 and four times for G. oxydans grown at oxygen limitation versus pH oxygen saturation in biological replicates.