Syntrophic interaction occurs during anaerobic fermentation of organic substances forming methane as the final product. H2 and formate are known to serve as the electron carriers in this process. Recently, it has been shown that direct interspecies electron transfer (DIET) occurs for syntrophic CH4 production from ethanol and acetate. Here, we constructed paddy soil enrichments to determine the involvement of DIET in syntrophic butyrate oxidation and CH4 production. The results showed that CH4 production was significantly accelerated in the presence of nanoFe3 O4 in all continuous transfers. This acceleration increased with the increase of nanoFe3 O4 concentration but was dismissed when Fe3 O4 was coated with silica that insulated the mineral from electrical conduction. NanoFe3 O4 particles were found closely attached to the cell surfaces of different morphology, thus bridging cell connections. Molecular approaches, including DNA-based stable isotope probing, revealed that the bacterial Syntrophomonadaceae and Geobacteraceae, and the archaeal Methanosarcinaceae, Methanocellales and Methanobacteriales, were involved in the syntrophic butyrate oxidation and CH4 production. Among them, the growth of Geobacteraceae strictly relied on the presence of nanoFe3 O4 and its electrical conductivity in particular. Other organisms, except Methanobacteriales, were present in enrichments regardless of nanoFe3 O4 amendment. Collectively, our study demonstrated that the nanoFe3 O4 -facilitated DIET occurred in syntrophic CH4 production from butyrate, and Geobacter species played the key role in this process in the paddy soil enrichments.

Deep eutectic solvents are found to be highly hygroscopic when exposed to the atmosphere.

Surface tension is a key physiochemical property for the application of deep eutectic solvents (DESs) in the field of interface and colloid. However, the surface tension of DESs has not been systematically studied. Here, a comprehensive investigation on the surface tension of 50 typical DESs was carried out. The effect of hydrogen-bonding donors (HBDs) and hydrogen-bonding acceptors (HBAs) on the surface tension was investigated. Furthermore, the surface tension of mixed systems of DESs with other solvents, water, water+salt (e.g., KCl), ethanol, acetone, isopropyl alcohol, and ethyl acetate (EtAc), was studied. It was found that both HBDs and HBAs had a significant influence on the surface tension of DESs. The presence of crystal water in the salt component of DESs would decrease the surface tension of DESs. Besides, the surface tension of DESs increased significantly when the water mole fraction was higher than 0.9, which was well consistent with the tendency of IR spectra. However, the surface tension of DESs decreased continuously with the increase of the mole ratio of other investigated solvents.

Magnetite nanoparticles (nanoFe3O4) have been reported to facilitate direct interspecies electron transfer (DIET) between syntrophic bacteria and methanogens thereby improving syntrophic methanogenesis. However, whether or how nanoFe3O4 affects acetotrophic methanogenesis remain unknown. Herein, we demonstrate the unique role of nanoFe3O4 in accelerating methane production from direct acetotrophic methanogenesis in Methanosarcina-enriched cultures, which was further confirmed by pure cultures of Methanosarcina barkeri. Compared with other nanomaterials of higher electrical conductivity such as carbon nanotubes and graphite, nanoFe3O4 with mixed valence Fe(II) and Fe(III) had the most significant stimulatory effect on methane production, suggesting its redox activity rather than electrical conductivity led to enhanced methanogenesis by M. barkeri. Cell morphology and spectroscopy analysis revealed that nanoFe3O4 penetrated into the cell membrane and cytoplasm of M. barkeri. These results provide the unprecedented possibility that nanoFe3O4 in the cell membrane of methanogens serve as electron shuttles to facilitate intracellular electron transfer and thus enhance methane production. This work has important implications not only for understanding the mechanisms of mineral-methanogen interaction but also for optimizing engineered methanogenic processes.

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Common organic volatile solvents would volatilize in air, thus causing air pollution and harming human health. Deep eutectic solvents (DESs) are one type of the green solvents with low volatility, deemed as the new solvents of the 21st century. Previous investigation showed that the DESs would undergo volatilization at high temperature and/or vacuum pressure. However, how DESs volatile at ambient temperature and pressure is unknown. Here the volatilization of DESs in air at ambient temperature and pressure was investigated by in situ FT−IR and 2D FT−IR. ChCl (choline chloride):Nmethylacetamide was taken as an example of DESs and we found that it underwent severely volatilization even at ambient temperature and pressure. Moreover, the dynamics process of the volatilization was investigated by 2D FT−IR. It was found that N-methylacetamide volatilizes from ChCl:N-methylacetamide by destroying the hydrogen bond between free NH group and ChCl in ChCl:N-methylacetamide during the first 60 min. H-bonded NH II with strong H-bonding interaction with ChCl also undergoes a remark alternation at this turning point at ca. 60 min. During the period from 60 and 190 min, there also exists free NH in the DES ChCl:N-methylacetamide. The shift of free NH group ceases after ca. 70 min. After 190 min, most of Nmethylacetamide in ChCl:N-methylacetamide have volatilized, only trace of N-methylacetamide is left, therefore, the shift of IR absorption peaks is negligible. This works shows that we should pay more attention to the volatilization of DESs even at ambient temperature and pressure.

Background Garlic is an entirely sterile crop with important value as a vegetable, condiment, and medicine. However, the evolutionary history of garlic remains largely unknown. Results Here we report a comprehensive map of garlic genomic variation, consisting of amazingly 129.4 million variations. Evolutionary analysis indicates that the garlic population diverged at least 100,000 years ago, and the two groups cultivated in China were domesticated from two independent routes. Consequently, 15.0 and 17.5% of genes underwent an expression change in two cultivated groups, causing a reshaping of their transcriptomic architecture. Furthermore, we find independent domestication leads to few overlaps of deleterious substitutions in these two groups due to separate accumulation and selection-based removal. By analysis of selective sweeps, genome-wide trait associations and associated transcriptomic analysis, we uncover differential selections for the bulb traits in these two garlic groups during their domestication. Conclusions This study provides valuable resources for garlic genomics-based breeding, and comprehensive insights into the evolutionary history of this clonal-propagated crop.