There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Microbial fuel cell (MFC) research is a rapidly evolving field that lacks established terminology and methods for the analysis of system performance. This makes it difficult for researchers to compare devices on an equivalent basis. The construction and analysis of MFCs requires knowledge of different scientific and engineering fields, ranging from microbiology and electrochemistry to materials and environmental engineering. Describing MFC systems therefore involves an understanding of these different scientific and engineering principles. In this paper, we provide a review of the different materials and methods used to construct MFCs, techniques used to analyze system performance, and recommendations on what information to include in MFC studies and the most useful ways to present results.

Microbial Fuel Cells: Methodology and Technology†

The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

American Society for Testing and Materials

Microbial fuel cell cathodes: from bottleneck to prime opportunity?

Hydrocarbons released during oil spills are persistent in marine sediments due to the absence of suitable electron acceptors below the oxic zone. Here, we investigated an alternative bioremediation strategy to remove toluene, a model monoaromatic hydrocarbon, using a bioanode. Bioelectrochemical reactors were inoculated with sediment collected from a hydrocarbon-contaminated marine site, and anodes were polarized at 0 mV and +300 mV (versus an Ag/AgCl [3 M KCl] reference electrode). The degradation of toluene was directly linked to current generation of up to 301 mA m(-2) and 431 mA m(-2) for the bioanodes polarized at 0 mV and +300 mV, respectively. Peak currents decreased over time even after periodic spiking with toluene. The monitoring of sulfate concentrations during bioelectrochemical experiments suggested that sulfur metabolism was involved in toluene degradation at bioanodes. 16S rRNA gene-based Illumina sequencing of the bulk anolyte and anode samples revealed enrichment with electrocatalytically active microorganisms, toluene degraders, and sulfate-reducing microorganisms. Quantitative PCR targeting the α-subunit of the dissimilatory sulfite reductase (encoded by dsrA) and the α-subunit of the benzylsuccinate synthase (encoded by bssA) confirmed these findings. In particular, members of the family Desulfobulbaceae were enriched concomitantly with current production and toluene degradation. Based on these observations, we propose two mechanisms for bioelectrochemical toluene degradation: (i) direct electron transfer to the anode and/or (ii) sulfide-mediated electron transfer.

Anodes stimulate anaerobic toluene degradation via sulfur cycling in marine sediments

A microbial community is engaged in a complex economy of co-operation and competition for carbon and energy. In engineered systems such as anaerobic digestion and fermentation, these relationships are exploited for conversion of a broad range of substrates into products, such as biogas, ethanol and carboxylic acids. Medium chain fatty acids (MCFA), for example hexanoic acid, are valuable, energy dense microbial fermentation products, however MCFA exhibit microbial toxicity to a broad range of microorganisms at low concentrations. Here we operated continuous mixed-population MCFA fermentations on biorefinery thin stillage to investigate the community response associated with the production and toxicity of MCFA. Here, an uncultured species from the Clostridium group IV (related to Clostridium sp. BS-1) became enriched in two independent reactors that produced hexanoic acid (up to 8.1 gL-1), octanoic acid (up to 3.2 gL-1), and trace concentrations of decanoic acid. Decanoic acid is reported here for the first time as a possible product of a Clostridium group IV species. Other species in the community, Lactobacillus spp. and Acetobacterium sp., generate intermediates in MCFA production, and their collapse in relative abundance resulted in an overall production decrease. A strong correlation was present between the community composition and both the hexanoic acid concentration (p = 0.026) and total VFA concentration (p = 0.003). MCFA suppressed species related to Clostridium sp. CPB-6 and Lactobacillus spp. to a greater extent than others. The proportion of the species related to Clostridium sp. BS-1 over Clostridium sp. CPB-6 had a strong correlation to the concentration of octanoic acid (p = 0.003). The dominance of this species and the increase in MCFA resulted in an overall toxic effect on the mixed community, most significantly on the Lactobacillus spp., which resulted in a decrease of total hexanoic acid concentration to 32  2 % below the steady state average. As opposed to the current view of MCFA toxicity broadly leading to production collapse, this study demonstrates that varied tolerance to MCFA within the community can lead to the dominance of some species and the suppression of others, which can result in a decreased productivity of the fermentation.

https://biblio.ugent.be/publication/8508357/file/8521742.pdf

A Clostridium Group IV Species Dominates and Suppresses a Mixed Culture Fermentation by Tolerance to Medium Chain Fatty Acids Products.

Hydrogen sulfide is ubiquitously present in many waste streams originating from industrial activities as well as in sewage. It needs to be removed as it is toxic, corrosive, and odorous. Conventional abatement strategies involve physicochemical methods, which require significant amounts of chemicals and/or high energy input. Considering the limitations of physicochemical methods, there is a need for more cost-effective and sustainable abatement strategies. Recent advances in electrode materials and operation have stimulated interest in electrochemical methods for pollutant remediation. Several electrochemical approaches for sulfide abatement have been proposed over the last few years. Electrochemical techniques offer several advantages including the avoidance of dosage, handling, transport and storage of potentially hazardous chemicals, and the possibility of recovering sulfide or sulfur from wastewater as a product. This paper reviews electrochemical strategies that have been proposed for removal of dissolved and gaseous hydrogen sulfide. The advantages and disadvantages as well as the economic potential of each of the proposed methods are discussed. The technical aspects and key challenges to enable full-scale implementation are highlighted. Finally, opportunities for expanding electrochemical methods for sulfide abatement are presented.

Electrochemical Abatement of Hydrogen Sulfide from Waste Streams

The treatment of wastewater containing sulfides in bioelectrochemical systems (BES) causes deposition of sulfur on the anode as a result of a solely electrochemical process. In this study, we investigate whether microorganisms can use this sulfur, rather than the anode or soluble sulfate, as an electron acceptor for the oxidation of acetate. Our results indicate that microorganisms use electrodeposited sulfur as preferable electron acceptor over the anode and sulfate and produce sulfide irrespective of electrochemical conditions. Bioelectrochemical and biological sulfide generation pathways were studied under different electrochemical conditions. The obtained results show that the sulfide generation rate at open circuit condition (anode potential −235 ± 5 mV versus standard hydrogen electrode, SHE) was higher in comparison to the electrochemical sulfide generation even at a lower potential of −275 mV (vs SHE), confirming that sulfide is produced through biological processes without any current generation. However, during closed circuit operation, the overall Coulombic efficiency (97% ± 2%) is not affected as the produced sulfide (originating from the reduction of deposited sulfur) is spontaneously reoxidized to sulfur when a favorable potential is maintained. This confirms the mediator role of sulfur during acetate oxidation in BES. A diagrammatic representation of the mechanism is proposed to characterize the interactions between acetate oxidation and sulfur conversions on the anode.

Korneel Rabaey

Papers

Microbial fuel cell cathodes: from bottleneck to prime opportunity?

Anodes stimulate anaerobic toluene degradation via sulfur cycling in marine sediments

A Clostridium Group IV Species Dominates and Suppresses a Mixed Culture Fermentation by Tolerance to Medium Chain Fatty Acids Products.

Electrochemical Abatement of Hydrogen Sulfide from Waste Streams

Role of Sulfur during Acetate Oxidation in Biological Anodes