Project description:Anode-associated multi-species exoelectrogenic biofilms are essential to the function of bioelectrochemical systems (BESs). The investigation of electrode-associated biofilms is critical to advance understanding of the function of individual members within communities that thrive using an electrode as the terminal electron acceptor. This study focusses on the analysis of a model biofilm community consisting of Shewanella oneidensis, Geobacter sulfurreducens and Geobacter metallireducens. The conducted experiments revealed that the organisms can build a stable biofilm on an electrode surface that is rather resilient to changes in the redox potential of the anode surface. The community operated at maximum electron transfer rates with electrode potentials of 0.04 V versus normal hydrogen electrode. Current densities decreased gradually with lower potentials and reached half-maximal values at -0.08 V. A positive interaction of the individual strains could be observed in our experiments. At least S. oneidensis and G. sulfurreducens show an upregulation of their central metabolism as a response to cultivation under mixed-species conditions. Interestingly, G. sulfurreducens was detected in the planktonic phase of the bioelectrochemical reactors only in mixed-culture experiments but not when it was grown in the absence of the other two organisms. It is possible that G. sulfurreducens cells used flavins which were released by S. oneidensis cells as electron shuttles. This would allow the organism to broaden its environmental niche. To the best of our knowledge, this is the first study describing the dynamics of biofilm formation of a model exoelectrogenic community, the resilience of the biofilm, and the molecular responses towards mixed-species conditions.
Project description:This SuperSeries is composed of the following subset Series: GSE22497: Transcriptome analysis of Geobacter sulfurreducens under multiple growth conditions GSE22503: ChIP-chip of Geobacter sulfurreducens PCA with antibody against RNAP and RpoD under various conditions GSE22511: Genome-wide transcription start site determination of Geobacter sulfurreducens under multiple growth conditions Refer to individual Series
Project description:This SuperSeries is composed of the following subset Series: GSE17834: Transcriptome analysis of Geobacter sulfurreducens grown with different nitrogen sources GSE17837: ChIP-chip of Geobacter sulfurreducens PCA with antibody against RpoN under various conditions. Refer to individual Series
Project description:There is a wide diversity of potential applications for direct electron transfer from electrodes to microorganisms, which might be better optimized if the mechanisms for this novel electrode-biofilm interaction were further understood. Geobacter sulfurreducens is one of the few microorganisms available in pure culture that is known to be capable of directly accepting electrons from a negatively poised electrode. Gene transcript abundance in cells of G. sulfurreducens using electrons delivered from a graphite electrode as the sole electron donor for fumarate reduction was compared with transcript abundance in cells growing on the same graphite material, but without an electrical connection and acetate as the electron donor.
Project description:Microtoming Coupled with Microarray Analysis to Evaluate Potential Differences in the Metabolic Status of Geobacter sulfurreducens at Different Depths in Anode Biofilms Differences in the Metabolic Status of Geobacter sulfurreducens at Different Depths in A Current Producing Biofilm Further insight into the metabolic status of cells within anode biofilms is essential for understanding the functioning of microbial fuel cells and developing strategies to optimize their power output. In order to further compare the metabolic status of cells growing close to the anode versus cells in the outer portion of the anode biofilm, mature anode biofilms were treated to stop turnover over of mRNA and then encased in resin which was sectioned into 100 nm shavings with a diamond knife and pooled into inner (0-20 µm from anode surface) and outer (30-60 µm) fractions. Whole genome DNA microarray analysis of RNA extracted from the shavings revealed that, at a 2-fold lower threshold, there were 146 genes that had significant (p<0.05), differences in transcript abundance between the inner and outer portions of the biofilm. Only 1 gene, GSU0093, a hypothetical ABC transporter, had significantly higher transcript abundances in the outer biofilm. Genes with lower transcript abundance in the outer biofilm included genes for ribosomal proteins and NADH dehydrogenase, suggesting that cells in the outer biofilm had lower metabolic rates. However, the differences in transcript abundance were relatively low (<3-fold) and the outer biofilm did not have significantly lower expression of the genes for TCA cycle enzymes which previous studies have demonstrated are sensitive indicators of changes in rates of metabolism in G. sulfurreducens. There also was no significant difference in the transcript levels for outer-surface cell components thought to be important in electron transfer in anode biofilms. Lower expression of genes involved in stress responses in the outer biofilm may reflect the development of low pH near the surface of the anode. The results of the metabolic staining and gene expression studies suggest that cells throughout the biofilm are metabolically active and can potentially contribute to current production. The microtoming/microarray strategy described here may be useful for evaluating gene expression with depth in a diversity of microbial biofilms.
Project description:Microtoming Coupled with Microarray Analysis to Evaluate Potential Differences in the Metabolic Status of Geobacter sulfurreducens at Different Depths in Anode Biofilms Differences in the Metabolic Status of Geobacter sulfurreducens at Different Depths in A Current Producing Biofilm Further insight into the metabolic status of cells within anode biofilms is essential for understanding the functioning of microbial fuel cells and developing strategies to optimize their power output. In order to further compare the metabolic status of cells growing close to the anode versus cells in the outer portion of the anode biofilm, mature anode biofilms were treated to stop turnover over of mRNA and then encased in resin which was sectioned into 100 nm shavings with a diamond knife and pooled into inner (0-20 µm from anode surface) and outer (30-60 µm) fractions. Whole genome DNA microarray analysis of RNA extracted from the shavings revealed that, at a 2-fold lower threshold, there were 146 genes that had significant (p<0.05), differences in transcript abundance between the inner and outer portions of the biofilm. Only 1 gene, GSU0093, a hypothetical ABC transporter, had significantly higher transcript abundances in the outer biofilm. Genes with lower transcript abundance in the outer biofilm included genes for ribosomal proteins and NADH dehydrogenase, suggesting that cells in the outer biofilm had lower metabolic rates. However, the differences in transcript abundance were relatively low (<3-fold) and the outer biofilm did not have significantly lower expression of the genes for TCA cycle enzymes which previous studies have demonstrated are sensitive indicators of changes in rates of metabolism in G. sulfurreducens. There also was no significant difference in the transcript levels for outer-surface cell components thought to be important in electron transfer in anode biofilms. Lower expression of genes involved in stress responses in the outer biofilm may reflect the development of low pH near the surface of the anode. The results of the metabolic staining and gene expression studies suggest that cells throughout the biofilm are metabolically active and can potentially contribute to current production. The microtoming/microarray strategy described here may be useful for evaluating gene expression with depth in a diversity of microbial biofilms. Three biological replicates were hybridized in triplicate on a coustom affimetrix tilling array using prokaryotic protocol (p69Affy, p75 Adobe) for labeling, hybridization and scanning.
Project description:This SuperSeries is composed of the following subset Series: GSE21312: Gene expression in a Geobacter sulfurreducens strain adapted for faster Fe(III) oxide reduction grown with ferric citrate as an electron acceptor GSE21313: Gene expression in a Geobacter sulfurreducens strain adapted for faster Fe(III) oxide reduction grown with fumarate as an electron acceptor Refer to individual Series
Project description:We gained insights into the environmental controls of Geobacter activities in cobamide-driven microbiomes by investigating the adaptive responses of the model representative G. sulfurreducens to growth and reproduction in the presence of CoII. Consistent with environmental exposure, we demonstrate high CoII resistance in this species and describe from genomic rand transcriptomic data multiple pathways for protein and DNA repair, cell envelope modifications, and biofilm formation that allow the cells to effectively cope with CoII stress. Importantly, we show that metal acclimation also involves respiratory chains for the reductive precipitation of the metal on the cell’s surface. These adaptive responses allow Geobacter species to grow in CoII-rich environments, sustaining the productivity of the native microbiomes and contributing to hitherto abiotic reactions of the Co cycle.