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:The formation of electroactive biofilms is a crucial process for the generation of bioelectricity and bioremediation. G. sulfurreducens is a dissimilatory metal-reducing microorganism that can couple oxidation of organic matter with extracellular electron transfer to different insoluble electron acceptors. It has the capability to form biofilms in insoluble metal oxides and electroconductive biofilms in electrodes in bioelectrochemical systems. The formation of electroactive biofilms in this microorganism is a process that has been studied from a physiological, genetic, physical, and electrochemical approach. In G. sulfurreducens, we found that the transcriptional regulator GSU1771 participates in the gene expression of essential genes involved in electron transfer and biofilm formation. Strains deficient in GSU1771 increases Fe(III) reduction, produces more c-type cytochromes and exopolysaccharides. Furthermore, the biofilms produced are thicker and more electroactive than wild-type. In this work, we investigate the global gene expression profile performing RNA-seq comparing Δgsu1771 mutant biofilm grown in non-conductive support (glass) and respiring-graphite electrode. RNA-seq analysis of Δgsu1771 biofilm grown in glass support revealed a total of 467 (167 upregulated and 300 downregulated) differentially expressed genes versus the wild-type biofilm. Meanwhile, in Δgsu1771 biofilm developed in respiring-electrode graphite, we detect 119 (79 upregulated and 40 downregulated) differentially expressed genes with respect to wild-type biofilm. Moreover, transcriptional changes of 67 (56 with the same regulation and in 11 counterregulation) genes were shared in Δgsu1771 biofilm developed in glass and graphite electrodes. We locate upregulated in Δgsu1771 biofilms potential target genes, involved in exopolysaccharide synthesis (gsu1961-63, gsu1959, gsu1972-73, gsu1976-77). We confirmed the upregulation of gsu1979, gsu0972, gsu0783, pgcA, omcM, aroG, panC gnfK, gsu2507, and the downregulation of asnA, ato-1, gsu0810, pilA, csrA, ppcD, and gsu3356 genes by RT-qPCR. DNA-protein binding assay shows direct binding of the GSU1771 regulator to the promoter region of pgcA, pulF, relA, and gsu3356. Also, heme-staining and western blotting revealed an increase of c-type cytochromes in Δgsu1771 biofilms such as OmcS and OmcZ. In general, our data shows that GSU1771 is a global regulator involved in controlling the extracellular electron transfer and exopolysaccharide synthesis, processes required for electroconductive biofilm development.
Project description:Biofilm formation by Escherichia coli was significantly inhibited when co-cultured with Stenotrophomonas maltophilia in static systems. Genes of E. coli involved in species interactions with S. maltophilia were identified in order to allow the study of the mechanisms of inhibited E. coli biofilm formation in co-culture. A total of 89 and 108 genes were identified as differentially expressed in mixed species cultures when growing as biofilm and as planktonic cultures, respectively, compared to the counterpart of pure cultured E. coli. Differential expression of certain identified genes was confirmed using E. coli reporter strains combined with single-cell based flow cytometry analysis. Co-culture with S. maltophilia affected genes involved in metabolism, signal transduction, cell wall composition, and biofilm formation of E. coli. Several selected genes were further confirmed as affecting E. coli biofilm formation in mixed species cultures with S. maltophilia. The data suggest that these genes were involved in species interactions between E. coli and S. maltophilia. This SuperSeries is composed of the SubSeries listed below.
Project description:Shewanella oneidensis MR-1 was grown on electrodes in electrochemical flow cells (EFC), and the transcriptome profiles of electrode-attached MR-1 cells were compared under electrolyte-flow and static (non-flow) conditions. The results revealed that the SO_3096 gene encoding a putative extracytoplasmic function (ECF) sigma factor, as well as genes related to cyclic-di-guanosine monophosphate and flagella synthesis (e.g., SO_3556 and flrC) and c-type cytochrome maturation (dsbD), was significantly up-regulated under the electrolyte-flow condition. Compared to wild-type MR-1 (WT), a deletion mutant of SO_3096 (∆SO_3096) showed an impaired biofilm formation and a decreased current generation in EFC, suggesting that the ECF sigma factor encoded by this gene is involved in the regulation of biofilm formation and current generation under electrolyte-flow conditions. We also compared the transcriptome profiles of WT and ∆SO_3096 grown in EFC, confirming that many genes up-regulated under the electrolyte-flow condition, including dsbD, were down-regulated in ∆SO_3096. Transcription analysis using lacZ as a reporter gene showed that the promoter of dsbD is activated in the presence of SO_3096. Measurement of current generation by a dsbD-deletion mutant revealed that this gene is essential for electron transfer to electrodes. These results suggest that the SO_3096 protein serves as an ECF sigma factor that regulates cellular functions related to electroactive biofilm formation under electrolyte-flow conditions.
Project description:Shewanella oneidensis MR-1 was grown on electrodes in electrochemical flow cells (EFC), and the transcriptome profiles of electrode-attached MR-1 cells were compared under electrolyte-flow and static (non-flow) conditions. The results revealed that the SO_3096 gene encoding a putative extracytoplasmic function (ECF) sigma factor, as well as genes related to cyclic-di-guanosine monophosphate and flagella synthesis (e.g., SO_3556 and flrC) and c-type cytochrome maturation (dsbD), was significantly up-regulated under the electrolyte-flow condition. Compared to wild-type MR-1 (WT), a deletion mutant of SO_3096 (∆SO_3096) showed an impaired biofilm formation and a decreased current generation in EFC, suggesting that the ECF sigma factor encoded by this gene is involved in the regulation of biofilm formation and current generation under electrolyte-flow conditions. We also compared the transcriptome profiles of WT and ∆SO_3096 grown in EFC, confirming that many genes up-regulated under the electrolyte-flow condition, including dsbD, were down-regulated in ∆SO_3096. Transcription analysis using lacZ as a reporter gene showed that the promoter of dsbD is activated in the presence of SO_3096. Measurement of current generation by a dsbD-deletion mutant revealed that this gene is essential for electron transfer to electrodes. These results suggest that the SO_3096 protein serves as an ECF sigma factor that regulates cellular functions related to electroactive biofilm formation under electrolyte-flow conditions.
Project description:Transcriptome analysis to determine the impact of oral exposure (in a sugar meal) to the liquid supernatant (i.e. LB culture media) of Chromobacterium sp. Panama biofilm culture. The biofilm supernatant (i.e. media) was first filtered with a 0.2uM filter to remove all live bacterial cells. It was then mixed with 10% sucrose, and a control sucrose meal was mixed with filtered LB. Mosquitoes were exposed to each sugar meal for 24 hours and then midguts were dissected from 20 adult females per treatment. The entire experiment was performed 4 independent times.
Project description:To explain enhanced biofilm formation and increased dissemination of S. epidermidis in mixed-species biofilms, microarrays were used to explore differential gene expression of S. epidermidis in mixed-species biofilms. One sample from single species biofilm (S1) and mixed-species biofilm (SC2) were excluded from analyses for outliers. We observed upregulation (2.7%) and down regulation (6%) of S. epidermidis genes in mixed-species biofilms. Autolysis repressors lrgA and lrgB were down regulated 36-fold and 27-fold respectively and was associated with increased eDNA possibly due to enhanced autolysis in mixed-species biofilms. These data suggest that bacterial autolysis and release of eDNA in the biofilm matrix may be responsible for enhancement and dissemination of mixed-species biofilms of S. epidermidis and C. albicans.
Project description:Biofilm formation by Escherichia coli was significantly inhibited when co-cultured with Stenotrophomonas maltophilia in static systems. Genes of E. coli involved in species interactions with S. maltophilia were identified in order to allow the study of the mechanisms of inhibited E. coli biofilm formation in co-culture. A total of 89 and 108 genes were identified as differentially expressed in mixed species cultures when growing as biofilm and as planktonic cultures, respectively, compared to the counterpart of pure cultured E. coli. Differential expression of certain identified genes was confirmed using E. coli reporter strains combined with single-cell based flow cytometry analysis. Co-culture with S. maltophilia affected genes involved in metabolism, signal transduction, cell wall composition, and biofilm formation of E. coli. Several selected genes were further confirmed as affecting E. coli biofilm formation in mixed species cultures with S. maltophilia. The data suggest that these genes were involved in species interactions between E. coli and S. maltophilia. This SuperSeries is composed of the SubSeries listed below. Refer to individual Series.