Microbial extracellular electron transfer plays an important role in diverse biogeochemical cycles, metal corrosion, bioelectrochemical technologies, and anaerobic digestion. Evaluation of electron uptake from pure Fe(0) and stainless steel indicated that, in contrast to previous speculation in the literature, Desulfovibrio ferrophilus and Desulfopila corrodens are not able to directly extract electrons from solid-phase electron-donating surfaces. D. ferrophilus grew with Fe(III) as the electron acceptor, but Dp. corrodens did not. D. ferrophilus reduced Fe(III) oxide occluded within porous alginate beads, suggesting that it released a soluble electron shuttle to promote Fe(III) oxide reduction. Conductive atomic force microscopy revealed that the D. ferrophilus pili are electrically conductive and the expression of a gene encoding an aromatics-rich putative pilin was upregulated during growth on Fe(III) oxide. The expression of genes for multi-heme ctype cytochromes was not upregulated during growth with Fe(III) as the electron acceptor, and genes for a porin-cytochrome conduit across the outer membrane were not apparent in the genome. The results suggest that D. ferrophilus has adopted a novel combination of strategies to enable extracellular electron transport, which may be of biogeochemical and technological significance.

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The effect of Co 2 C crystal facets on the selectivity of C 2 species (C 2 oxygenates and hydrocarbons) in Fischer−Tropsch synthesis (FTS) reaction was investigated using density functional theory calculations, and the selectivity comparisons among five exposed Co-termination ( 101), ( 011), ( 010), (110), and (111) crystal facets are examined to shed light on the essential relationship between FTS selectivity and the structure of Co 2 C crystal facets. The results show that the C−C bond of C 2 species prefers to be formed instead of C 1 species CH 4 over Co 2 C catalysts in the FTS reaction, and the selectivity of C 2 species and the dominant existence form of key CH x intermediates are sensitive to the crystal facet of Co 2 C catalysts, which are closely associated with Co 2 C crystal facet's electronic and structural properties. The electronic and structural properties of different Co 2 C crystal facets show that the high selectivity of C 2 oxygenates over the ( 011) and ( 111) facets are attributed to the upshift of their surface d-band centers, as well as the presence of the step B 5 -type active unit with five Co atoms consisted of much denser surface active sites. However, both ( 101) and ( 010) facets exhibit high selectivity toward C 2 hydrocarbons, and the (110) facet presents high selectivity toward the formation of CH 4 . Thus, regulating the exposed crystal facets of Co 2 C catalyst can control the selectivity of desirable C 2 species. This work provides evidence at a molecular level to support that the sensitivity of Co 2 C crystal facet is a cause to affect the selectivity of desired products in the FTS reaction.

The accelerated use of iron oxide nanoparticles (IONPs) and multi-wall carbon nanotubes (MWCNTs) in the consumer and industrial sectors has triggered the need to understand their potential environmental impact. The response of anaerobic granular sludge (AGS) to IONPs and MWCNTs during the anaerobic digestion of beet sugar industrial wastewater (BSIW) was investigated in this study. The IONPs increased the biogas and subsequent CH production rates in comparison with MWCNTs and the control samples. This might be due to the utilization of IONPs and MWCNTs as conduits for electron transfer toward methanogens. The MWCNTs majorly enriched the bacterial growth, while IONP enrichment mostly benefitted the archaea population. Furthermore, scanning electron microscopy and confocal laser scanning microscopy revealed that AGS produced extracellular polymeric substances, which interacted with the IONPs and MWCNTs. This provided cell protection and prevented the nanoparticles from piercing through the membranes and thus cytotoxicity. The results provide useful information and insights on the adjustment of anaerobic microorganisms to the natural complex environment based on nanoparticles infiltration.

A giant planar Hall effect (PHE) and anisotropic magnetoresistance (AMR) is observed in TaP, a nonmagnetic Weyl semimetal with ultrahigh mobility. The perpendicular resistivity (i.e., the planar magnetic field applied normal to the current) far exceeds the zero-field resistivity, which thus rules out the possible origin of negative longitudinal magnetoresistance. The giant PHE/AMR is finally attributed to the large anisotropic orbital magnetoresistance that stems from the ultrahigh mobility.Furthermore, the mobility-enhanced current jetting effects are found to strongly deform the line shape of the curves, and their evolution with the changing magnetic field and temperature is also studied. Although the giant PHE/AMR suggests promising applications in spintronics, the enhanced current jetting shows the other side of the coin, which needs to be considered in the future device design.

Besides the negative longitudinal magnetoresistance (MR), planar Hall effect (PHE)is a newly emerging experimental tool to test the chiral anomaly or nontrivial Berry curvature in Weyl semimetals (WSMs). However, the origins of PHE in various systems are not fully distinguished and understood. Here we perform a systematic study on the PHE and anisotropic MR (AMR) of Td-MoTe2, a type-II WSM. Although the PHE and AMR curves can be well fitted by the theoretical formulas, we demonstrate that the anisotropic resistivity arises from the orbital MR (OMR), instead of the negative MR as expected in the chiral anomaly effect. In contrast, the absence of negative MR indicates that the large OMR dominates over the chiral anomaly effect. This explains why it is difficult to measure negative MR in type-II WSMs. We argue that the measured PHE can be related with the chiral anomaly only when the negative MR is simultaneously observed.

Impact statement Methane‐producing microorganisms accelerate the corrosion of iron‐containing metals. Previous studies have inferred that some methanogens might directly accept electrons from Fe(0), but when this possibility was more intensively investigated, H2 was shown to be an intermediary electron carrier between Fe(0) and methanogens. Here, we report that Methanosarcina acetivorans catalyzes direct metal‐to‐microbe electron transfer to support methane production. Deletion of the gene for the multiheme, outer‐surface c‐type cytochrome MmcA eliminated methane production from Fe(0), consistent with the key role of MmcA in other forms of extracellular electron exchange. These findings, coupled with the previous demonstration that outer‐surface c‐type cytochromes are also electrical contacts for electron uptake from Fe(0) by Geobacter and Shewanella species, suggest that the presence of multiheme c‐type cytochromes on corrosion surfaces might be diagnostic for direct metal‐to‐microbe electron transfer and that interfering with cytochrome function might be a strategy to mitigate corrosion.

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