Soil domestication by rice cultivation results in plant-soil feedback through shifts in soil microbiota.

BackgroundSoils are a key component of agricultural productivity, and soil microbiota determine the availability of many essential plant nutrients. Agricultural domestication of soils, that is, the conversion of previously uncultivated soils to a cultivated state, is frequently accompanied by intensive monoculture, especially in the developing world. However, there is limited understanding of how continuous cultivation alters the structure of prokaryotic soil microbiota after soil domestication, including to what extent crop plants impact soil microbiota composition, and how changes in microbiota composition arising from cultivation affect crop performance.ResultsWe show here that continuous monoculture (> 8 growing seasons) of the major food crop rice under flooded conditions is associated with a pronounced shift in soil bacterial and archaeal microbiota structure towards a more consistent composition, thereby domesticating microbiota of previously uncultivated sites. Aside from the potential effects of agricultural cultivation practices, we provide evidence that rice plants themselves are important drivers of the domestication process, acting through selective enrichment of specific taxa, including methanogenic archaea, in their rhizosphere that differ from those of native plants growing in the same environment. Furthermore, we find that microbiota from soils domesticated by rice cultivation contribute to plant-soil feedback, by imparting a negative effect on rice seedling vigor.ConclusionsSoil domestication through continuous monoculture cultivation of rice results in compositional changes in the soil microbiota, which are in part driven by the rice plants. The consequences include a negative impact on plant performance and increases in greenhouse gas emitting microbes

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Magnetic PSA-Fe 3 O 4 @C 3D mesoporous microsphere as anode for lithium ion batteries

Fe3O4 has long been regarded as one of the most promising anode materials for lithium ion batteries due to its high theoretical capacity, low cost, and nontoxic properties. Here, we report a facile hydrothermal way to perform carbonization of poly (ST-AN) (PSA) to obtain a PSA-Fe3O4@C3Dmesoporousmicrosphere. (∗) Its electrochemical performance as an anode material was evaluated by cyclic voltammetry (CV) and galvanostatic charge/discharge experiments. The PSA-Fe3O4@C electrode delivers a capacity of 1130 mA h g-1 at 0.5 C, in contrast to that of the CA (Citric Acid)-Fe3O4@C (1111 mA h g-1) and Fe3O4 (817 mA h g-1). The improvements can be attributed to the unique composition and microstructure that endow the electrode with large contact area between material and electrolyte, short diffusion path for lithium ions transportation in the active material, low electron transfer resistance from a current collector to the active material, and large buffering space for volume change during charging/discharging process.Department of Electrical Engineerin