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This research was developed to investigate whether inoculation with Azospirillum brasilense in combination with silicon (Si) can enhance N use efficiency (NUE) in wheat and to evaluate and correlate nutritional and productive components and wheat grain yield. The study was carried out on a Rhodic Hapludox under a no-till system with a completely randomized block design with four replications in a 2 × 2 × 5 factorial scheme: two liming sources (with Ca and Mg silicate as the Si source and limestone); two inoculations (control - without inoculation and seed inoculation with A . brasilense ) and five side-dress N rates (0, 50, 100, 150 and 200 kg ha −1 ). The results of this study showed positive improvements in wheat growth production parameters, NUE and grain yield as a function of inoculation associated with N rates. Inoculation can complement and optimize N fertilization, even with high N application rates. The potential benefits of Si use were less evident; however, the use of Si can favour N absorption, even when associated with A . brasilense . Therefore, studies conducted under tropical conditions with Ca and Mg silicate are necessary to better understand the role of Si applied alone or in combination with growth-promoting bacteria such as A . brasilense .

The extraction of K(+) and SiO(2 )from silicate minerals by Bacillus mucilaginosus in liquid culture was studied in incubation experiments. B. mucilaginosus was found to dissolve soil minerals and mica and simultaneously release K(+) and SiO(2) from the crystal lattices. In contrast, the bacterium did not dissolve feldspar. B. mucilaginosus also produced organic acids and polysaccharides during growth. The polysaccharides strongly adsorbed the organic acids and attached to the surface of the mineral, resulting in an area of high concentration of organic acids near the mineral. The polysaccharides also adsorbed SiO(2) and this affected the equilibrium between the mineral and fluid phases and led to the reaction toward SiO(2 )and K(+) solubilization. These two processes led to the decomposition of silicate minerals by the bacterium.

The performance of two bacteria, Arthrobacter viscosus and Streptococcus equisimilis , and the effect of the interaction of these bacteria with four different clays on the retention of diethylketone were investigated in batch experiments. The uptake, the removal percentages and the kinetics of the processes were determined. S. equisimilis , by itself, had the best performance in terms of removal percentage, for all the initial diethylketone concentrations tested: 200, 350 and 700 mg/L. The uptake values are similar for both bacteria. A possible mechanism to explain the removal of diethylketone includes its degradation by bacteria, followed by the adsorption of the intermediates/sub-products by the functional groups present on the cells' surfaces. The assays performed with bacteria and clays indicated that the uptake values are similar despite of the clay used, for the same microorganism and mass of clay, but in general, higher values are reached when S. equisimilis is used, compared to A. viscosus . Kinetic data were described by pseudo-first- and pseudo-second-order models.

Depending on toothpaste formulation, part of the fluoride is insoluble and would not be totally absorbable in the gastrointestinal tract, thus changing dental fluorosis risk estimation. This hypothesis was tested with formulations with either all fluoride in a soluble form (NaF/SiO 2 -based toothpaste, 1,100 µg F/g as labeled, 1,129.7 ± 49.4 µg F/g soluble fluoride as analyzed) or with around 20% of insoluble fluoride (Na 2 FPO 3 /CaCO 3 -based toothpaste, 1,450 µg F/g as labeled, 1,122.4 ± 76.4 µg F/g soluble fluoride as analyzed). Toothpastes were evaluated either fresh or after accelerated aging, which increased insoluble fluoride to 40% in the Na 2 FPO 3 /CaCO 3 -based toothpaste. In a blind, crossover clinical trial conducted in five legs, 20 adult volunteers ingested 49.5 µg of total fluoride/kg body weight from each formulation or purified water (control). Whole saliva and urine were collected as bioavailability indicators, and pharmacokinetics parameters calculated showed significantly (p < 0.05) lower fluoride bioavailability for Na 2 FPO 3 /CaCO 3 toothpaste, which was reduced further after aging. A significant correlation between the amount of soluble fluoride ingested, but not total fluoride, and fluoride bioavailability was found (r = 0.57, p < 0.0001). The findings suggest that the estimated fluorosis risk as a result of ingestion of Na 2 FPO 3 /CaCO 3 -based toothpastes should be calculated based on the toothpaste’s soluble rather than total fluoride concentration.

Legume trees form an abundant and functionally important component of tropical forests worldwide with N₂-fixing symbioses linked to enhanced growth and recruitment in early secondary succession. However, it remains unclear how N₂-fixers meet the high demands for inorganic nutrients imposed by rapid biomass accumulation on nutrient-poor tropical soils. Here, we show that N₂-fixing trees in secondary Neotropical forests triggered twofold higher in situ weathering of fresh primary silicates compared to non-N₂–fixing trees and induced locally enhanced nutrient cycling by the soil microbiome community. Shotgun metagenomic data from weathered minerals support the role of enhanced nitrogen and carbon cycling in increasing acidity and weathering. Metagenomic and marker gene analyses further revealed increased microbial potential beneath N₂-fixers for anaerobic iron reduction, a process regulating the pool of phosphorus bound to iron-bearing soil minerals. We find that the Fe(III)-reducing gene pool in soil is dominated by acidophilic Acidobacteria, including a highly abundant genus of previously undescribed bacteria, Candidatus Acidoferrum, genus novus. The resulting dependence of the Fe-cycling gene pool to pH determines the high iron-reducing potential encoded in the metagenome of the more acidic soils of N₂-fixers and their nonfixing neighbors. We infer that by promoting the activities of a specialized local microbiome through changes in soil pH and C:N ratios, N₂-fixing trees can influence the wider biogeochemical functioning of tropical forest ecosystems in a manner that enhances their ability to assimilate and store atmospheric carbon.

Carbonic anhydrase (CA) plays an important role in the formation and evolution of life. However, to our knowledge, there has been no report on CA isoenzyme function differentiation in fungi. Two different CA gene sequences in Aspergillus nidulans with clear genetic background provide us a favorable basis for studying function differentiation of CA isoenzymes. Heterologously expressed CA1 was used to test its weathering ability on silicate minerals and real‐time quantitative PCR was used to detect expression of the CA1 and CA2 genes at different CO2 concentrations and in the presence of different potassium sources. The northern blot method was applied to confirm the result of CA1 gene expression. Heterologously expressed CA1 significantly promoted dissolution of biotite and wollastonite, and CA1 gene expression increased significantly in response to soluble K‐deficiency. The northern blot test further showed that CA1 participated in K‐feldspar weathering. In addition, the results showed that CA2 was primary involved in adapting to CO2 concentration change. Taken together, A. nidulans can choose different CA to meet their survival needs, which imply that some environmental microbes have evolved different CAs to adapt to changes in CO2 concentration and acquire mineral nutrition so that they can better adapt to environmental changes. Inversely, their adaption may impact mineral weathering and/or CO2 concentration, and even global change. One of the two CA genes is a preference gene when A. nidulans grows in special living environments. CA1 is involved mainly with the acquisition of mineral elements, while CA2 mainly adapts to changes in CO2 concentration. The directional selection of A. nidulans CA isozyme can ease some of the adverse effects on life processes brought about by external changes in the environment. It can also help A. nidulans avoid the waste of materials and energy caused by the gene's overexpression. Inversely, their adaption may impact mineral weathering and/or CO2 concentration, and even global change.

Background Diatoms, which can accumulate large amounts of carotenoids, are a major group of microalgae and the dominant primary producer in marine environments. Phaeodactylum tricornutum , a model diatom species, acquires little silicon for its growth although silicon is known to contribute to gene regulation and play an important role in diatom intracellular metabolism. In this study, we explored the effects of artificial high-silicate medium (i.e. 3.0 mM sodium metasilicate) and LED illumination conditions on the growth rate and pigment accumulation in P. tricornutum , which is the only known species so far that can grow without silicate. It’s well known that light-emitting diodes (LEDs) as novel illuminants are emerging to be superior monochromatic light sources for algal cultivation with defined and efficient red and blue lights. Results Firstly, we cultivated P. tricornutum in a synthetic medium supplemented with either 0.3 mM or 3.0 mM silicate. The morphology and size of diatom cells were examined: the proportion of the oval and triradiate cells decreased while the fusiform cells increased with more silicate addition in high-silicate medium; the average length of fusiform cells also slightly changed from 14.33 µm in 0.3 mM silicate medium to 12.20 µm in 3.0 mM silicate medium. Then we cultivated P. tricornutum under various intensities of red light in combination with the two different levels of silicate in the medium. Higher biomass productivity also achieved in 3.0 mM silicate medium than in 0.3 mM silicate medium under red LED light irradiation at 128 μmol/m 2 /s or higher light intensity. Increasing silicate reversed the down-regulation of fucoxanthin and chlorophyll a under high red-light illumination (i.e. 255 μmol/m 2 /s). When doubling the light intensity, fucoxanthin content decreased under red light but increased under combined red and blue (50:50) lights while chlorophyll a content reduced under both conditions. Fucoxanthin accumulation and biomass productivity increased with enhanced red and blue (50:50) lights. Conclusion High-silicate medium and blue light increased biomass and fucoxanthin production in P. tricornutum under high light conditions and this strategy may be beneficial for large-scale production of fucoxanthin in diatoms.

DNA origami has proven useful for organizing diverse nanoscale components into patterns with 6 nm resolution. However for many applications, such as nanoelectronics, large-scale organization of origami into periodic lattices is desired. Here, we report the self-assembly of DNA origami rectangles into two-dimensional lattices based on stepwise control of surface diffusion, implemented by changing the concentrations of cations on the surface. Previous studies of DNA–mica binding identified the fractional surface density of divalent cations as the parameter which best explains the behaviour of linear DNA on mica. We show that for between 0.04 and 0.1, over 90% of DNA rectangles were incorporated into lattices and that, compared with other functions of cation concentration, best captures the behaviour of DNA rectangles. This work shows how a physical understanding of DNA–mica binding can be used to guide studies of the higher-order assembly of DNA nanostructures, towards creating large-scale arrays of nanodevices for technology. DNA origami is useful for organizing nanoscale objects, and linear arrays of DNA origami have previously been assembled via programmable bonds based on DNA base-stacking. Here, such ‘stacking bonds’ are used to assemble large 2D lattices of DNA origami by a novel cation-controlled surface diffusion mechanism.

Sepiolite nanofibers, which are natural silicates belonging to the clay mineral family, could be promising potential nanocarriers for the nonviral transfer of biomolecules. The physicochemical characteristics of sepiolite make it capable of binding various types of biological molecules, including polysaccharides, lipids, proteins and viruses. Sepiolite nanofibers have also been shown to bind effectively to various types of DNA molecules through electrostatic interactions, hydrogen bonds, cationic bridges and van der Waals forces. In this study, we analyzed the adsorption of DNA and proteins to sepiolite by analyzing the competition among these biomolecules during the adsorption process. To determine the binding of sepiolite to proteins, we used BSA and a monoclonal antibody (mAb) against the CD4 membrane antigen as a model. The binding efficiency was measured by adsorption isotherms. Zeta potential measurements of the suspensions were performed using a Brookhaven NanoBrook 90 Plus PALS instrument. We show here that the adsorption of proteins to sepiolite is increased in the presence of CaCl and is charge-dependent and that sepiolite can adsorb proteins even when their net charges are equal to those on its surface. Coating of sepiolite with DNA (Sep/DNA bionanocomposites) reduces the absorption efficiency of both BSA and mAb, and this can be rescued by CaCl . Conversely, preincubation of sepiolite with BSA or the mAb decreased the efficiency of DNA binding; Ca restored the binding efficiency for BSA but not for the mAb. Changes in pH result in changes in the net charge of proteins, influencing the amount of protein adsorbed. Although various types of protein interactions with mineral clays have been described, our results confirm that electrostatic forces are among the primary interactions in the adsorption process. These results pave the way for the use of biohybrids as a new class of nanoplatform for gene transfer with potential clinical applications.

Bioturbation is a key process affecting nutrient cycling in soft sediments. The invasive polychaete genus Marenzelleria spp. has established successfully throughout the Baltic Sea increasing species and functional diversity with possible density-dependent effects on bioturbation and associated solute fluxes. We tested the effects of increasing density of M. arctia, M. viridis and M. neglecta on bioturbation and solute fluxes in a laboratory experiment. Benthic communities in intact sediment cores were manipulated by adding increasing numbers of Marenzelleria spp. The results showed that Marenzelleria spp. in general enhanced all bioturbation metrics, but the effects on solute fluxes varied depending on the solute, on the density and species identity of Marenzelleria , and on the species and functional composition of the surrounding community. M. viridis and M. neglecta were more important in predicting variation in phosphate and silicate fluxes, whereas M. arctia had a larger effect on nitrogen cycling. The complex direct and indirect pathways indicate the importance of considering the whole community and not just species in isolation in the experimental studies. Including these interactions provides a way forward regarding our understanding of the complex ecosystem effects of invasive species.