Project description:The gene expression profile of wild-type Desulfovibrio vulgaris grown on cathodic hydrogen, generated at an iron electrode surface with an imposed negative potential of -1.1 V (cathodic protection conditions). The gene expression profile of cells grown on cathodic hydrogen was compared to that of cells grown with gaseous hydrogen bubbling through the culture. Relative to the latter, the electrode-grown cells over-expressed two hydrogenases, the hyn1 genes for [NiFe] hydrogenase-1, and the hyd genes, encoding [Fe] hydrogenase. The hmc genes for the high molecular weight cytochrome (Hmc) complex, which allows electron flow from the hydrogenases across the cytoplasmic membrane, were also over-expressed. In contrast, cells grown on gaseous hydrogen over-expressed the hys genes for [NiFeSe] hydrogenase. Cells growing on the electrode also over-expressed genes encoding proteins which promote biofilm formation. Although the gene expression profiles for these two modes of growth were distinct, they were more closely related to each other than to that for cells grown in a lactate- and sulfate-containing medium. Electrochemically measured corrosion rates were lower for iron electrodes covered with hyn1-, hyd-, and hmc-mutant biofilms, as compared to wild-type biofilms. This confirms the importance, suggested by the gene expression studies, of the corresponding gene products in D. vulgaris-mediated iron corrosion. Keywords: Growth on Iron Electrode and Biofilm formation
Project description:The gene expression profile of wild-type Desulfovibrio vulgaris grown on cathodic hydrogen, generated at an iron electrode surface with an imposed negative potential of -1.1 V (cathodic protection conditions). The gene expression profile of cells grown on cathodic hydrogen was compared to that of cells grown with gaseous hydrogen bubbling through the culture. Relative to the latter, the electrode-grown cells over-expressed two hydrogenases, the hyn1 genes for [NiFe] hydrogenase-1, and the hyd genes, encoding [Fe] hydrogenase. The hmc genes for the high molecular weight cytochrome (Hmc) complex, which allows electron flow from the hydrogenases across the cytoplasmic membrane, were also over-expressed. In contrast, cells grown on gaseous hydrogen over-expressed the hys genes for [NiFeSe] hydrogenase. Cells growing on the electrode also over-expressed genes encoding proteins which promote biofilm formation. Although the gene expression profiles for these two modes of growth were distinct, they were more closely related to each other than to that for cells grown in a lactate- and sulfate-containing medium. Electrochemically measured corrosion rates were lower for iron electrodes covered with hyn1-, hyd-, and hmc-mutant biofilms, as compared to wild-type biofilms. This confirms the importance, suggested by the gene expression studies, of the corresponding gene products in D. vulgaris-mediated iron corrosion. Keywords: Growth on Iron Electrode and Biofilm formation For each condition 2 unique biological samples were hybridized to 4 arrays that each contained duplicate spots. Genomic DNA was used as universal reference.
Project description:Identification of putative proteins of interest that are involved in cathodic electron uptake by the novel iron-corroding strain D. ferrophilus IS5
Project description:<p>Understanding the extracellular electron transfer mechanisms of electroactive bacteria could help determine their potential in microbial fuel cells (MFCs) and their microbial syntrophy with redox-active minerals in natural environments. However, the mechanisms of extracellular electron transfer to electrodes by sulfate-reducing bacteria (SRB) remain underexplored. Here, we utilized double-chamber MFCs with carbon cloth electrodes to investigate the extracellular electron transfer mechanisms of Desulfovibrio vulgaris Hildenborough (DvH), a model SRB, under varying lactate and sulfate concentrations using different DvH mutants. Our MFC setup indicated that DvH can harvest electrons from lactate at the anode and transfer them to cathode, where DvH could further utilize these electrons. Patterns in current production compared to variations of electron donor/acceptor ratios in the anode and cathode suggested that attachment of DvH to the electrode and biofilm density were critical for effective electricity generation. Electron microscopy analysis of DvH biofilms indicated DvH utilized filaments that resemble pili to attach on electrodes and facilitate extracellular electron transfer from cell-to-cell and to the electrode. Proteomics profiling indicated that DvH adapted to electroactive respiration by presenting more pili- and flagellar- related proteins. The mutant with a deletion of the major pilus-producing gene yielded less voltage and far less attachment to both anodic and cathodic electrodes, suggesting the importance of pili in extracellular electron transfer. The mutant with a deficiency in biofilm formation, however, did not eliminate current production indicating the existence of indirect extracellular electron transfer. Untargeted metabolomics profiling showed flavin-based metabolites, potential electron shuttles.</p>
Project description:To identify novel genes modulating Candida albicans biofilm formation, a screen of 2451 overexpression strains allowed us to identify 16 genes whose overexpression significantly reduced biofilm formation. Genome-wide expression and binding analyses were conducted upon overexpression of ZCF15 and ZCF26 and wild type planktonic and biofilm cells were performed. A ChIP assays was performed. Briefly, untagged strain (CEC4665) and two replicates each of ZCF15 (CEC5929 and CEC5930) and ZCF26 (CEC5931 and CEC5932) strain were grown in biofilm condition for 18 h and cells were cross-linked with 1% final concentration of formaldehyde for 25 min at 30°C.The DNA was immunoprecipitated with anti-protein A antibodies (Sigma Aldrich Cat. No. P3775). The immunoprecipitated (IP) DNA were used to determine the binding of Zcf15 and Zcf26 across the genome by ChIP-sequencing