Community analysis of biofilms on flame-oxidized stainless steel anodes in microbial fuel cells fed with different substrates

BackgroundThe flame-oxidized stainless steel anode (FO-SSA) is a newly developed electrode that enhances microbial fuel cell (MFC) power generation; however, substrate preference and community structure of the biofilm developed on FO-SSA have not been well characterized. Herein, we investigated the community on FO-SSA using high-throughput sequencing of the 16S rRNA gene fragment in acetate-, starch-, glucose-, and livestock wastewater-fed MFCs. Furthermore, to analyze the effect of the anode material, the acetate-fed community formed on a common carbon-based electrode—carbon-cloth anode (CCA)—was examined for comparison.ResultsSubstrate type influenced the power output of MFCs using FO-SSA; the highest electricity was generated using acetate as a substrate, followed by peptone, starch and glucose, and wastewater. Intensity of power generation using FO-SSA was related to the abundance of exoelectrogenic genera, namely Geobacter and Desulfuromonas, of the phylum Proteobacteria, which were detected at a higher frequency in acetate-fed communities than in communities fed with other substrates. Lactic acid bacteria (LAB)—Enterococcus and Carnobacterium—were predominant in starch- and glucose-fed communities, respectively. In the wastewater-fed community, members of phylum Planctomycetes were frequently detected (36.2%). Exoelectrogenic genera Geobacter and Desulfuromonas were also detected in glucose-, starch-, and wastewater-fed communities on FO-SSA, but with low frequency (0–3.2%); the lactate produced by Carnobacterium and Enterococcus in glucose- and starch-fed communities might affect exoelectrogenic bacterial growth, resulting in low power output by MFCs fed with these substrates. Furthermore, in the acetate-fed community on FO-SSA, Desulfuromonas was abundant (15.4%) and Geobacter had a minor proportion (0.7%), while in that on CCA, both Geobacter and Desulfuromonas were observed at similar frequencies (6.0–9.8%), indicating that anode material affects exoelectrogenic genus enrichment in anodic biofilm.ConclusionsAnodic community structure was dependent on both substrate and anode material. Although Desulfuromonas spp. are marine microorganisms, they were abundant in the acetate-fed community on FO-SSA, implying the presence of novel non-halophilic and exoelectrogenic species in this genus. Power generation using FO-SSA was positively related to the frequency of exoelectrogenic genera in the anodic community. Predominant LAB in saccharide-fed anodic biofilm caused low abundance of exoelectrogenic genera and consequent low power generation

Community analysis of biofilms on flame-oxidized stainless steel anodes in microbial fuel cells fed with different substrates

Abstract Background The flame-oxidized stainless steel anode (FO-SSA) is a newly developed electrode that enhances microbial fuel cell (MFC) power generation; however, substrate preference and community structure of the biofilm developed on FO-SSA have not been well characterized. Herein, we investigated the community on FO-SSA using high-throughput sequencing of the 16S rRNA gene fragment in acetate-, starch-, glucose-, and livestock wastewater-fed MFCs. Furthermore, to analyze the effect of the anode material, the acetate-fed community formed on a common carbon-based electrode—carbon-cloth anode (CCA)—was examined for comparison. Results Substrate type influenced the power output of MFCs using FO-SSA; the highest electricity was generated using acetate as a substrate, followed by peptone, starch and glucose, and wastewater. Intensity of power generation using FO-SSA was related to the abundance of exoelectrogenic genera, namely Geobacter and Desulfuromonas, of the phylum Proteobacteria, which were detected at a higher frequency in acetate-fed communities than in communities fed with other substrates. Lactic acid bacteria (LAB)—Enterococcus and Carnobacterium—were predominant in starch- and glucose-fed communities, respectively. In the wastewater-fed community, members of phylum Planctomycetes were frequently detected (36.2%). Exoelectrogenic genera Geobacter and Desulfuromonas were also detected in glucose-, starch-, and wastewater-fed communities on FO-SSA, but with low frequency (0–3.2%); the lactate produced by Carnobacterium and Enterococcus in glucose- and starch-fed communities might affect exoelectrogenic bacterial growth, resulting in low power output by MFCs fed with these substrates. Furthermore, in the acetate-fed community on FO-SSA, Desulfuromonas was abundant (15.4%) and Geobacter had a minor proportion (0.7%), while in that on CCA, both Geobacter and Desulfuromonas were observed at similar frequencies (6.0–9.8%), indicating that anode material affects exoelectrogenic genus enrichment in anodic biofilm. Conclusions Anodic community structure was dependent on both substrate and anode material. Although Desulfuromonas spp. are marine microorganisms, they were abundant in the acetate-fed community on FO-SSA, implying the presence of novel non-halophilic and exoelectrogenic species in this genus. Power generation using FO-SSA was positively related to the frequency of exoelectrogenic genera in the anodic community. Predominant LAB in saccharide-fed anodic biofilm caused low abundance of exoelectrogenic genera and consequent low power generation

Identification of the gene for disaggregatase from Methanosarcina mazei

The gene sequences encoding disaggregatase (Dag), the enzyme responsible for dispersion of cell aggregates of Methanosarcina mazei to single cells, were determined for three strains of M. mazei (S-6T, LYC and TMA). The dag genes of the three strains were 3234 bp in length and had almost the same sequences with 97% amino acid sequence identities. Dag was predicted to comprise 1077 amino acid residues and to have a molecular mass of 120 kDa containing three repeats of the DNRLRE domain in the C terminus, which is specific to the genus Methanosarcina and may be responsible for structural organization and cell wall function. Recombinant Dag was overexpressed in Escherichia coli and preparations of the expressed protein exhibited enzymatic activity. The RT-PCR analysis showed that dag was transcribed to mRNA in M. mazei LYC and indicated that the gene was expressed in vivo. This is the first time the gene involved in the morphological change of Methanosarcina spp. from aggregate to single cells has been identified

Nickel ions selectively inhibit lipopolysaccharide-induced interleukin-6 production by decreasing its mRNA stability.

Nickel (Ni) ions easily elute from many alloys and elicit inflammation and allergies. Previous studies have shown that infections due to the implantation of medical devices cause inflammation and enhance the elution of Ni ions (Ni²⁺). However, cross-talk between infection- and Ni²⁺-induced signaling pathways has not yet been elucidated in detail. In the present study, we investigated the effects of Ni2+ on the lipopolysaccharide (LPS)-induced production of cytokines in a LPS-induced air pouch-type inflammation model in BALB/c mice and the murine macrophage cell line RAW264. We demonstrated that Ni²⁺ inhibited the LPS-induced production of interleukin (IL)-6, but not that of tumor necrosis factor (TNF)-α both in vivo and in vitro. This inhibitory effect was also observed with cobalt ion (Co²⁺), but not with chloride ion (Cl⁻), zinc ion (Zn²⁺), or palladium ion (Pd²⁺), and was highly selective to the production of IL-6. Ni²⁺ did not inhibit the activation of ERK1/2, p38 MAPK, or JNK. Although Ni²⁺ decreased IL-6 mRNA levels, it failed to inhibit the LPS-induced activation of the IL-6 promoter. An experiment using actinomycin D, a transcription inhibitor, revealed that Ni²⁺ decreased the stability of IL-6 mRNA. Moreover, Ni²⁺ inhibited the LPS-induced expression of Arid5a, but not regnase-1. These results demonstrated that Ni²⁺ may have selectively inhibited the LPS-induced production of IL-6 by decreasing the Arid5a-dependent stabilization of IL-6 mRNA

Synthesis of regioselectively monosubstituted propargyl derivatives of γ-cyclodextrin

Additional file 1: Figure S1. XPS narrow spectra of Fe2p (A), Cr2p (B), and Ni2p (C) for FO-SS and untreated SS

Time course of IL-6 and TNF-α expression and effects of NiCl2 on the stability of IL-6 and TNF-α mRNA.

<p>RAW264 cells were incubated in medium containing LPS (1 μg/ml) in the presence or absence of NiCl₂ (300 μM) for the indicated time. (A and B) IL-6 (A) and TNF-α mRNA (B) levels were measured by quantitative real-time PCR. Values are normalized to those of GAPDH and the mean value of the control was set to 1.0. (C and D) IL-6 (C) and TNF-α (D) concentrations were determined by ELISA. Data represent the mean ± S.E.M. (n = 3, 4). (E and F) RAW264 cells were incubated in medium containing LPS (1 μg/ml) in the presence or absence of NiCl₂ (300 μM). After the 4 h stimulation, AcD (5 μg/ml) was added and the cells were further incubated for the indicated time. IL-6 (E) and TNF-α (F) mRNA levels were determined by quantitative real-time PCR. Values are normalized to those of GAPDH and the mean value of the control at time 0 was set to 1.0. Data represent the mean ± S.E.M. (<i>n</i> = 4). **<i>p</i> < 0.01 vs. vehicle, <i>#p</i> < 0.05 and <i>##p</i> < 0.01 vs. LPS. Data are representative of two independent experiments.</p

Effects of various metal ions on the LPS-induced production of IL-6 and TNF-α in RAW264 cells.

<p>RAW264 cells were incubated for 8 h in medium containing LPS (1 μg/ml) (A, B, and C), poly(I:C) (50 μg/ml) (D), or zymosan A (500 μg/ml) (E) in the presence or absence of NiCl₂ or NiSO₄ at the indicated concentrations, or 300 μM of NiCl₂, CoCl₂, ZnCl₂, or PdCl₂ (B and C). The concentrations of IL-6 and TNF-α in the medium were determined by ELISA and cell viability was determined by the MTT assay. The mean value of the control was set to 1.0 (C). Data represent the mean ± S.E.M. (<i>n</i> = 3, 4). **<i>p</i> < 0.01 between the indicated groups. Data are representative of three independent experiments.</p

MOESM2 of Enhanced electrical power generation using flame-oxidized stainless steel anode in microbial fuel cells and the anodic community structure

Additional file 2: Figure S2. SEM images of the biofilms binding to FO-SSA, untreated SSA, and CCA. The bars represent 0.1 mm