Relative Abundance Of Geobacter Research Articles

Calcium carbonate enhanced As uptake in Pteris vittata by increasing pH and As bioavailability and mediating rhizosphere As-transformation bacterial community

Pteris vittata is the first reported arsenic (As) hyperaccumulator, which is also a calcium (Ca) indicator and adapts to calcareous environment. Therefore, it is hypothesized that Ca plays a role in As accumulation but detail effects and mechanisms are unclear. Typical Ca-compounds (CaCO3, Ca3(PO4)2 and CaSO4) were added to hydroponics. CaCO3 and Ca3(PO4)2 increased pH by 0.75 and 0.31, while CaSO4 decreased it by 0.26. Besides, CaCO3 increased As concentration in P. vittata frond by 25.8 % from 65.4 to 82.3 mg kg–1, while Ca3(PO4)2 and CaSO4 decreased it by 15.1–38.2 % to 40.4–55.5 mg kg–1. So the effect of CaCO3 on soil pH, As bioavailability and As-transformation bacterial community was further examined. In pots, CaCO3 increased soil pH by 0.57 and increased bioavailable As concentration by 6.2 μg kg–1, thereby induced 27.3–28.5 % promotion in As plant accumulation. Rhizosphere bacterial community variance can be explained by soil pH and bioavailable As changes at 49–66 %. P. vittata frond As concentration was negatively correlated with rhizosphere As-transformation bacterial diversity (arrA and arsM) (R=-0.57 and -0.66), and positively correlated with the relative abundance of Geobacter (R=0.66) and Pseudomanas (R=0.48), which mediating As mobilization and transformation. This indicated that CaCO3 can enhance As uptake by P. vittata via increasing soil pH, As bioavailability and mediating As-transformation bacterial community in the rhizosphere. The information helps to better understand how calcareous environment-adaptation benefits P. vittata to uptake and accumulate As. This helps to strategize more efficient processes for As-contaminated soils remediation using the hyperaccumulating plants.

Potassium channel blocker selectively enriched Geobacter from mixed-cultured electroactive biofilm: Insights from microbial community, functional prediction and gene expressions

This study investigated the effects of electrical signaling disruption induced by adding tetraethylammonium (TEA, a potassium channel blocker) on the formation of mixed-cultured electroactive biofilms, especially the relative abundance of Geobacter over time. Results showed that TEA addition decelerated the biofilm formation, but selectively enriched Geobacter over time (45.8% on Day 32, 67.7% on Day 60 and 78.1% on Day 90), thus resulting in higher final extracellular electron transfer (EET) efficiency. Redundancy analysis (RDA) confirmed that TEA and operation time were significant factors for the selective enrichment of Geobacter. Moreover, increase in cellular processes and signal processing by PICRUSt analysis indicated adaptive responses of electrogenic biofilms to electrical signaling disruption. Furthermore, qRT-PCR indicated the compensatory roles of key cytochromes and pilA in electrochemical communication, which induced Geobacter enrichment. This work provided a broader understanding of electroactive biofilm regulation and potential applications for electricity generation and biosensor in the future.

GO/iron series systems enhancing the pH shock resistance of anaerobic systems for sulfate-containing organic wastewater treatment.

In this study, the effect of pH shock during the treatment of sulfate-containing organic wastewater was investigated using an anaerobic fermentation system reinforced with graphene oxide (GO)/iron series systems. The results show that the anaerobic system with the GO/iron series systems exhibited enhanced resistance to pH shock. Among them, the GO/Fe0 system had the strongest resistance to pH shock, the systems of GO/Fe3O4 and GO/Fe2O3 followed close behind, while the blank system performed the worst. After pH shock, the CODCr removal rate, SO42− removal rate, and gas production of the GO/Fe0 group were significantly improved compared with those of the control group by 51.0%, 65.3%, and 34.6%, respectively, while the accumulation of propionic acid was the lowest. Further, detailed microbial characterization revealed that the introduction of the GO/iron series systems was beneficial to the formation of more stable anaerobic co-metabolic flora in the system, and the relative abundance of Geobacter, Clostridium, Desulfobulbus and Desulfovibrio increased after acidic and alkaline shock.

Dissolved organic carbon drives nutrient cycling via microbial community in paddy soil

Microbial mediated iron cycling drives the biogeochemical cycling of carbon, nitrogen, sulfur, and phosphorus. However, the fate of the microbial community and the relative metabolic pathways in paddy soil after the addition of biogas slurry are poorly understood. In this study, the response of functional genes was investigated by growing one-season rice in paddy soils in a pot experiment. Seven treatments were prepared: 1) control (CK); 2) organic carbon (OC); 3) fertilizer (F); 4) 5% of biogas slurry (B05); 5) 10% of biogas slurry (B10); 6) 15% of biogas slurry (B15); 7) 20% of biogas slurry (B20). In the biogas slurry treatments, Geobacter increased more than in the other treatments during rice growth, which were structured by TOC. Particularly, in the B10 treatment, the relative abundance of Geobacter was 1.6 and 14.8 times higher than that of CK at the heading and mature stages, respectively. At the heading stage, the addition of biogas slurry and OC shifted the microbial phosphorus-transformation communities differently. There were no significant differences in the carbon, nitrogen, and sulfur metabolic pathways between the two treatments. At the mature stage, the carbon: nitrogen: phosphorus balance was significantly influenced by the regulation of functional gene expression and metabolic activities. These findings provide insight into the key factors affecting carbon, nitrogen, sulfur, phosphorus, and iron during rice growth after carbon inputs.

Promoting direct interspecies electron transfer and acetoclastic methanogenesis for enhancing anaerobic digestion of butanol octanol wastewater by coupling granular activated carbon and exogenous hydrogen

Butanol octanol wastewater (BOW) generated from syngas conversion of coal contained abundant toxic organic pollutants. Anaerobic digestion is a promising technology for BOW, but abundant toxic substances would inhibit the activity of anaerobic microorganisms. Granular activated carbon (GAC) and exogenous hydrogen (EH2) were employed to enhance anaerobic digestion of BOW. The results indicated that methane production increased to 289.55 ± 17.43 mL CH4/g COD in EH2/GAC group, which was 1.07, 2.04, and 1.98 times of that in GAC, EH2, and control groups, respectively. In EH2/GAC group. The relative abundance of Geobacter and Methanosaeta increased rapidly to 25.36% and 52.81%, respectively, and the relative abundance of Clostridium was 9.78%. The underlying mechanism might be that GAC promoted the enrichment of Geobacter, and EH2 changed metabolic mechanism of Clostridium, stimulating the enrichment of Methanosaeta. Direct interspecies electron transfer was promoted by EH2/GAC, thus improving the methane production rate of BOW.

Magnetite-enhanced bioelectrochemical stimulation for biodegradation and biomethane production of waste activated sludge

Microbial electrolytic cell (MEC) and magnetite (M) have shown excellent performance in promoting anaerobic digestion (AD) of biowastes. In this study, four types of anaerobic systems (i.e. single AD, M-AD, MEC-AD, and M-MEC-AD) were developed to comprehensively investigate the potential effects of magnetite-enhanced bioelectrochemical stimulation on the biodegradation of waste activated sludge (WAS) and methane (CH4) production. Results showed that M-MEC-AD system produced the highest cumulative CH4 yield, 9.4% higher than that observed in MEC-AD system. Bioelectrochemical stimulation enriched electroactive Geobacter, and classical methanogens (Methanosaeta and Methanobacterium), and the proliferation was further promoted when coupling with magnetite. The relative abundance of Geobacter (6.9%), Methanosaeta (0.3%), and Methanobacterium (12.6%) in M-MEC-AD system was about 10.8, 1.2, and 1.2 times of MEC-AD system, respectively. The integration of magnetite could serve as the conductive materials, and promote inherent indirect electron transfer (IET) and emerging direct electron transfer (DET) between methanogens and fermentative bacteria, building a more energy-efficient route for interspecies electron transfer and methane productivity. This study demonstrated the positive promotion of the coupled bioelectrochemical regulation and magnetite on organic biodegradation, process stability and CH4 productivity, providing some references for the integrated technology in sludge treatment and bioenergy recovery.

Biochar and magnetite promote methanogenesis during anaerobic decomposition of rice straw

Conductive materials like magnetite nanoparticles (nanoFe3O4) are known to stimulate methanogenesis from syntrophic oxidation of butyrate and propionate. Whether conductive materials increase the decomposition of complex organic substrates like plant residues is unknown. Here, we investigated the effects of biochar and nanoFe3O4 on anaerobic decomposition of rice straw and methanogenesis in a rice paddy soil. The straw decomposition and CH4 production were greatly stimulated by both treatments. Major bacterial populations were Bacteroidetes, Clostridia, Deltaproteobacteria, Actinobacteria and Anaerolineae, while methanogens were predominately Methanosarcina, Methanosaeta and Methanobacterium. Bacteroides were relatively enriched in the biochar treatment, while the Deltaproteobacteria and Anaerolineae were favored by nanoFe3O4. The relative abundance of typical syntrophs including Syntrophomonas, Syntrophus and Smithella were positively correlated with the degradation of intermediate short-chain fatty acids. Notably, the relative abundance of Geobacter, which increased during the incubation, was approximately tenfold greater than all other syntrophs. The co-occurrence of Geobacter together with Methanosarcina and Methanosaeta suggests that the enhanced decomposition of rice straw and methanogenesis by biochar and magnetite may be related to direct interspecies electron transfer involved in the syntrophic oxidation of intermediate products.

Activated carbon stimulates microbial diversity and PAH biodegradation under anaerobic conditions in oil-polluted sediments

Biodegradation by microorganisms is a useful tool that helps alleviating hydrocarbon pollution in nature. Microbes are more efficient in degradation under aerobic than anaerobic conditions, but the majority of sediment by volume is generally anoxic. Incubation experiments were conducted to study the biodegradation potential of naphthalene—a common polycyclic aromatic hydrocarbon (PAH)—and the diversity of microbial communities in presence/absence of activated carbon (AC) under aerobic/anaerobic conditions. Radio-respirometry experiments with endogenous microorganisms indicated that degradation of naphthalene was strongly stimulated (96%) by the AC addition under anaerobic conditions. In aerobic conditions, however, AC had no effects on naphthalene biodegradation. Bioaugmentation tests with cultured microbial populations grown on naphthalene showed that AC further stimulated (92%) naphthalene degradation in anoxia. Analysis of the 16S rRNA gene sequences implied that sediment amendment with AC increased microbial community diversity and changed community structure. Moreover, the relative abundance of Geobacter, Thiobacillus, Sulfuricurvum, and methanogenic archaea increased sharply after amendment with AC under anaerobic conditions. These results may be explained by the fact that AC particles promoted direct interspecies electron transfer (DIET) between microorganisms involved in PAH degradation pathways. We suggest that important ecosystem functions mediated by microbes—such as hydrocarbon degradation—can be induced and that AC enrichment strategies can be exploited for facilitating bioremediation of anoxic oil-contaminated sediments and soils.

Magnet anode enhances extracellular electron transfer and enrichment of exoelectrogenic bacteria in bioelectrochemical systems

BackgroundOptimizing the ability of exoelectrogens is a key factor in boosting the overall efficiency of bioelectrochemical systems. In this study, we construct magnetic microbial fuel cells (MFCs) with magnets with different static magnetic field (SMF) intensities for use as anodes. It is proposed as an in situ study of the effects of magnetic fields on the performance and exoelectrogenic biofilm of bioelectrochemical system.ResultsThe magnetic MFCs obtain a 71.0–105% increase in voltage production and a 42.9–104% increase in power density compared with non-magnetic MFCs. MFCs with a MF intensity of 80 mT obtain the best performances. SMF decreases the internal resistance of MFCs, especially its diffusion resistance. The relative abundance of Geobacter in magnetic MFCs is up to 32.5% higher than that of non-magnetic MFC. SMFs also lead to the shifts in microbial community structure of methanogens.ConclusionThe constructed magnetic MFCs obtained better performance compared with the non-magnetic MFC, in terms of voltage production, power density, and coulombic efficiency. The relative abundance of Geobacter spp. (one kind of exoelectrogen) was much higher in the magnetic MFCs. The optimal static magnetic field intensity for enriching exoelectrogens is around 80 mT. It is likely that the decrease of internal resistance, enrichment in exoelectrogens, and the syntrophic interactions between exoelectrogens and methanogens result in the enhanced performance of magnetic MFCs. This study provides a magnetic method for the enrichment of exoelectrogens, which can be extensively applied in bioelectrochemical systems.

Improved performance of the microbial electrolysis desalination and chemical-production cell with enlarged anode and high applied voltages

The aim of this study was to improve performance of the microbial electrolysis desalination and chemical-production cell (MEDCC) using enlarged anode and high applied voltages. MEDCCs with anode lengths of 9 and 48cm (i.e., the 9cm-anode MEDCC and 48cm-anode MEDCC, respectively) were tested under different voltages (1.2–3.0V). Our results demonstrated for the first time that the MEDCC could maintain high performance even under the applied voltage higher than that for water dissociation (i.e., 1.8V). Under the applied voltage of 2.5V, the maximum current density in the 48cm-anode MEDCC reached 32.8±2.6A/m2, which is one of the highest current densities reported so far in the bioelectrochemical system (BES). The relative abundance of Geobacter was changed along the anode length. Our results show the great potential of the BES with enlarged anode and high applied voltages.

Effect of in-situ immobilized anode on performance of the microbial fuel cell with high concentration of sodium acetate

To improve performance of the microbial fuel cell (MFC) with high concentration of organics, a procedure for in-situ immobilized anode with agarose gel was proposed in this study. The performance of power generation, electrochemical activity, and microbial community of the MFC with immobilized anode (i-MFC) was investigated using different concentrations (i.e., 1, 5, 10, and 20g/L) of sodium acetate. The i-MFC could generate electricity within one hour after refreshing substrate. With 5g/L acetate, the maximum voltages were 560 and 460mV in the i-MFC and controlled MFC (c-MFC), respectively. With 10g/L acetate, the maximum voltage of the i-MFC was much higher than that of the c-MFC (500 vs. 300mV). With the acetate concentrations of 5 and 10g/L, the maximum power densities in the i-MFC were 610±50 and 370±40mW/m2, respectively, while the maximum power densities in the c-MFC were 343±30 and 240±20mW/m2, respectively. Cyclic voltammetry measurements indicated that microbial activity of the i-MFC anode was higher than that of the c-MFC anode under the high acetate concentration (3.00 vs. 2.19mA). The relative abundance of Geobacter on the i-MFC anode was much higher than that on the c-MFC anode (62% vs. 40%). The in-situ immobilization strategy provided an easily performed and efficient way to keep the activity of exoelectrogens, resulting in the improvement of MFC performance.

Comparison of microbial taxonomic and functional shift pattern along contamination gradient.

BackgroundThe interaction mechanism between microbial communities and environment is a key issue in microbial ecology. Microbial communities usually change significantly under environmental stress, which has been studied both phylogenetically and functionally, however which method is more effective in assessing the relationship between microbial communities shift and environmental changes still remains controversial.ResultsBy comparing the microbial taxonomic and functional shift pattern along heavy metal contamination gradient, we found that both sedimentary composition and function shifted significantly along contamination gradient. For example, the relative abundance of Geobacter and Fusibacter decreased along contamination gradient (from high to low), while Janthinobacterium and Arthrobacter increased their abundances. Most genes involved in heavy metal resistance (e.g., metc, aoxb and mer) showed higher intensity in sites with higher concentration of heavy metals. Comparing the two shift patterns, there were correlations between them, because functional and phylogenetic β-diversities were significantly correlated, and many heavy metal resistance genes were derived from Geobacter, explaining their high abundance in heavily contaminated sites. However, there was a stronger link between functional composition and environmental drivers, while stochasticity played an important role in formation and succession of phylogenetic composition demonstrated by null model test.ConclusionsOverall our research suggested that the responses of functional traits depended more on environmental changes, while stochasticity played an important role in formation and succession of phylogenetic composition for microbial communities. So profiling microbial functional composition seems more appropriate to study the relationship between microbial communities and environment, as well as explore the adaptation and remediation mechanism of microbial communities to heavy metal contamination.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0731-6) contains supplementary material, which is available to authorized users.

Electricity generation and microbial community changes in microbial fuel cells packed with different anodic materials

Four materials, carbon felt cube (CFC), granular graphite (GG), granular activated carbon (GAC) and granular semicoke (GS) were tested as packed anodic materials to seek a potentially practical material for microbial fuel cells (MFCs). The microbial community and its correlation with the electricity generation performance of MFCs were explored. The maximum power density was found in GAC, followed by CFC, GG and GS. In GAC and CFC packed MFCs, Geobacter was the dominating genus, while Azospira was the most populous group in GG. Results further indicated that GAC was the most favorable for Geobacter adherence and growth, and the maximum power densities had positive correlation with the total biomass and the relative abundance of Geobacter, but without apparent correlation with the microbial diversity. Due to the low content of Geobacter in GS, power generated in this system may be attributed to other microorganisms such as Synergistes, Bacteroidetes and Castellaniella.