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: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:Xiangjiang River (Hunan, China) has been contaminated with heavy metal for several decades by surrounding factories. However, little is known about the influence of a gradient of heavy metal contamination on the diversity, structure of microbial functional gene in sediment. To deeply understand the impact of heavy metal contamination on microbial community, a comprehensive functional gene array (GeoChip 5.0) has been used to study the functional genes structure, composition, diversity and metabolic potential of microbial community from three heavy metal polluted sites of Xiangjiang River.
Project description:Xiangjiang River (Hunan, China) has been contaminated with heavy metal for several decades by surrounding factories. However, little is known about the influence of a gradient of heavy metal contamination on the diversity, structure of microbial functional gene in sediment. To deeply understand the impact of heavy metal contamination on microbial community, a comprehensive functional gene array (GeoChip 5.0) has been used to study the functional genes structure, composition, diversity and metabolic potential of microbial community from three heavy metal polluted sites of Xiangjiang River. Three groups of samples, A, B and C. Every group has 3 replicates.
Project description:Prolific heterotrophic biofilm growth is a common occurrence in airport receiving streams containing deicer and anti-icer runoff. This study investigated relations of heterotrophic biofilm prevalence and community composition to environmental conditions at stream sites upstream and downstream of Milwaukee Mitchell International Airport in Milwaukee, WI, during two deicing seasons (2009–2010 and 2010–2011). Modern genetic tools (such as microarray) have not previously been applied to biofilm communities in this type of setting. We used microarray results to characterize biofilm community composition as well as the response of the biofilm community to environmental factors (i.e., organic content (using chemical oxygen demand concentration) and temperature).
Project description:AgNPs was added to MFCs, exposed for 7 days, and recovered for 14 days after stopping the addition. The effects of AgNPs recovery after exposure on electroactive microorganisms and EET of MFC anode biofilm were studied.
Project description:Biofilm lifestyle is critical for bacterial pathogens to colonize and protect themselves from host immunity and antimicrobial chemicals in plants and animals. The formation and regulation mechanism of phytobacterial biofilm are still obscure. Here, we found that Ralstonia solanacearum Resistance to ultraviolet C (RuvC) is highly abundant in biofilm and positively regulates pathogenicity by governing systemic movement in tomato xylem. RuvC protein accumulates at the later stage of biofilm and specifically targets the Holliday junction (HJ) like structures to disrupt biofilm extracellular DNA (eDNA) lattice, thus facilitating biofilm dispersal. Recombinant RuvC protein can resolve extracellular HJ prevent bacterial biofilm formation. Heterologous expression of R. solanacearum or Xanthomonas oryzae pv. oryzae RuvC with plant secretion signal in tomato or rice confers resistance to bacterial wilt or bacterial blight disease, respectively. Plant chloroplast localized HJ resolvase monokaryotic chloroplast 1 (MOC1) which is structural similar to bacterial RuvC shows a strong inhibit effect on bacterial biofilm formation. Re-localization of SlMOC1 to apoplast in tomato roots leads to increase resistance to bacterial wilt. Our novel finding reveals a critical pathogenesis mechanism of R. solanacearum and provides an efficient biotechnology strategy to improve plant resistance to bacteria vascular disease.