Are nitrogen and carbon cycle processes impacted by common stream antibiotics? A comparative assessment of single vs. mixture exposures

A variety of antibiotics are ubiquitous in all freshwater ecosystems that receive wastewater. A wide variety of antibiotics have been developed to kill problematic bacteria and fungi through targeted application, and their use has contributed significantly to public health and livestock management. Unfortunately, a substantial fraction of the antibiotics applied to humans, pets and livestock end up in wastewater, and ultimately many of these chemicals enter freshwater ecosystems. The effect of adding chemicals that are intentionally designed to kill microbes, on freshwater microbial communities remains poorly understood. There are reasons to be concerned, as microbes play an essential role in nutrient uptake, carbon fixation and denitrification in freshwater ecosystems. Chemicals that reduce or alter freshwater microbial communities might reduce their capacity to degrade the excess nutrients and organic matter that characterize wastewater. We performed a laboratory experiment in which we exposed microbial community from unexposed stream sediments to three commonly detected antibiotics found in urban wastewater and urban streams (sulfamethoxazole, danofloxacin, and erythromycin). We assessed how the form and concentration of inorganic nitrogen, microbial carbon, and nitrogen cycling processes changed in response to environmentally relevant doses (10 μg/L) of each of these antibiotics individually and in combination. We expected to find that all antibiotics suppressed rates of microbial mineralization and nitrogen transformations and we anticipated that this suppression of microbial activity would be greatest in the combined treatment. Contrary to our expectations we measured few significant changes in microbially mediated functions in response to our experimental antibiotic dosing. We found no difference in functional gene abundance of key nitrogen cycling genes nosZ, mcrA, nirK, and amoA genes, and we measured no treatment effects on NO3- uptake or N2O, N2, CH4, CO2 production over the course of our seven-day experiment. In the mixture treatment, we measured significant increases in NH4+ concentrations over the first 24 hours of the experiment, which were indistinguishable from controls within six hours. Our results suggest remarkable community resistance to pressure antibiotic exposure poses on naïve stream sediments.

Effects of Selenium on the Chlorophylls, Gas Exchange, Antioxidant Activity and Amino Acid Composition of Lettuce Grown under an Aquaponics System

Aquaponics is a sustainable technique that is respectful to the environment, as it reuses products and minimizes the consumption of new materials. The combination of this technique with the foliar application of selenium (as Na2SeO4) could lead to healthier and more sustainable products, which are increasingly requested by consumers. Lettuce (Lactuca sativa L.) plants were grown in an aquaponics system (fish water) as compared with a control (conventional soilless fertigation), and sprayed with different concentrations of selenium (0, 4, 8, and 16 µmol L−1). The results showed a reduction in the dry weight and N content of lettuce plants irrigated with the fish water mixture treatment. However, the application of Se relieved this stress, increasing the photosynthetic rate and ABTS, and reducing the content of chlorophylls, β-carotene, and several of the measured amino acids. The best results were observed with the highest concentration of Se (16 µmol L−1), as an increase in nitrogen content was observed, as shown by a greater weight of the plant. Furthermore, this treatment produced the greatest increase in ABTS and the least reduction in amino acid content. This novel study highlights the possibility of improving the efficiency of N utilization in lettuce by applying foliar selenium in combination with an aquaponics system.

The Effect of Seaweed Spirulina Platensis Extract and Micronutrients on Wheat Yield and Yield Components

Many literatures have reviewed and confirmed the importance of the seaweed extract in terms of improving crop yield. A field experiment was carried out during winter season at Izzah Heuristic Farm in Wasit Province, Iraq to examine the effect of combination of seaweed extract and micronutrient fertiliser on some wheat cultivars. Three cultivars were used in this experiment as well as four stimulator treatments: control (no added extract), seaweed extract, micronutrient, and a combination of both of them. A randomized completely blocked design (RCBD) with a factorial arrangement and three replicates was used in this experiment. The results showed that BHTH cultivar had significantly largest number of spikes, spike length, number of grains per spike, kernel weight and grain yield. The mixture treatment enhanced grain yield of all cultivars was better treatment compared with the others. In terms of the interactions, BHTH cultivars in the mixture treatment had the greatest grain yield and other components. It is clear that a combination of marine algae with micronutrient fertiliser can improve the crop grain yield and its component and can be recommended for farmers to enhance grain production. However, further study might be better step for further exploration about the impact of seaweed extract and micronutrient fertiliser with further rates and other crops or crop cultivars.

Production of Alginate from Persian Gulf Sargassum angustifolium Seaweeds: Novel Extraction and Characterization Methods

Background: Brown seaweeds contain polysaccharides, minerals, proteins, pigments, polyphenols, and fatty acids. Several of these compounds show a wide range of biological activities, such as anticoagulant, anti-tumor, antiviral, and anti-cancer effects. Objectives: This study was designed to evaluate the extraction, purification, and characterization of alginate from Sargassum angustifolium simultaneous with fucoidan extraction and the effect of this process on the structure and properties of alginate. Methods: The extraction of alginate from S. angustifolium was carried out using defatting with organic solvents mixture, treatment with acid-base solutions, and purification with absolute ethanol. The novel characterization of this compound was carried out by the Fourier transform infrared spectroscopy (FT-IR), FT-NMR, energy dispersive X-ray (EDX), and florescent spectrophotometry methods. Results: The fluorescent emission of alginate showed 66.54% removal of impurities, such as phenolic compounds. The FT-IR analysis showed the carboxyl and hydroxyl groups as significant signals in the alginate structure. By analyzing the anomeric protons and other aspects of 1H-NMR, M/G ratio, FG, FM, FGG, FMM, FMG (or FGM) were determined to be 0.61, 0.62, 0.38, 0.31, 0.07, and 0.31, respectively. The intrinsic viscosity and molecular weight of alginate were 0.9 dL/g and 41.53 kDa, respectively. Conclusions: The total amount of alginate from the residual S. angustifolium was 17% of dried seaweed. The structure elucidation of alginate was performed with the FT-IR, FT-NMR, and EDX methods.

Effects of Microelements on Downy Mildew (Peronospora belbahrii) of Sweet Basil

We recently demonstrated that spraying or irrigating with Ca, Mg and K reduces the severity of sweet basil downy mildew (SBDM). Here, the effects of Mn, Zn, Cu and Fe on SBDM were tested in potted plants. The effects of Mn and Zn were also tested under semi-commercial and commercial-like field conditions. Spray applications of a mixture of EDTA-chelated microelements (i.e., Fe-EDTA, Mn-EDTA, Zn-EDTA, Cu-EDTA and Mo) reduces SBDM severity. The application of EDTA chelates of individual microelements (i.e., Fe-EDTA, Mn-EDTA and Zn-EDTA) significantly reduces SBDM in potted plants. Foliar applications of Mn-EDTA and Zn-EDTA are found to be effective under semi-commercial conditions and were, thus, further tested under commercial-like conditions. Under commercial-like conditions, foliar-applied Mn-EDTA and Zn-EDTA decreased SBDM severity by 46–71%. When applied through the irrigation solution, those two microelements reduce SBDM by more than 50%. Combining Mg with Mn-EDTA and Zn-EDTA in the irrigation solution does not provide any additional disease reduction. In the commercial-like field experiment, the microelement-mixture treatment, applied as a spray or via the irrigation solution, was combined with fungicides spray treatments. This combination provides synergistic disease control. The mode of action in this plant–pathogen system may involve features of altered host resistance.

Inconsistent effects of species diversity and N fertilization on soil microbes and carbon storage in perennial bioenergy cropping systems

Positive relationships between plant species diversity, soil microbial function and nutrient cycling have been well documented in natural systems, and these relationships have the potential to improve the production and sustainability of agroecosystems. Our objectives were to study the long-term effects of planted species composition and nitrogen (N) fertilization on soil microbial biomass C, extracellular enzyme activity, changes in total soil C, soil fertility and aboveground biomass yield in mixtures of native prairie species managed with and without N fertilizer for bioenergy production at four sites in Minnesota (MN), USA. Species were sown into mixture treatments and composition was not maintained (i.e., no weeding) throughout the duration of the study. Species mixture treatments at establishment included a switchgrass (Panicum virgatum L.) monoculture (SG), a four-species grass mixture (GM), an eight-species legume/grass mixture (LG) and a 24-species high diversity forb/legume/grass mixture (HD). Species diversity and aboveground productivity were similar for most mixture treatments at final sampling after 11 or 12 years of succession. Despite this homogenization of productivity and diversity throughout the study, the effects of planted species diversity and a decade of succession resulted in some differences in soil variables across species mixture treatments. On a peat soil in Roseau, MN, soil enzyme activities including β-glucosidase (BG), cellobiohydrolase (CBH) and phosphatase (PHOS) were highest in HD compared to GM treatments. On a sandy soil at Becker, MN, total soil C increased in all treatment combinations at the 0–15 and 15–30 cm depth intervals, with SG showing greater increases than HD at the 15–30 cm depth. Final soil pH also varied by species mixture at the Becker and Roseau sites, but differences in treatment comparisons varied by location. Nitrogen fertilization did not affect any response variable alone, but interacted with species mixture treatment to influence PHOS and total soil C at Becker. The inconsistent effects of species mixture and N fertilization on soil biological and chemical properties observed across sites highlight the importance of local soil and climate conditions on bioenergy and ecosystem service provisioning of perennial bioenergy cropping systems.

Bacillus Benefits the Growth of Ambrosia Artemisiifolia by Increasing Available Nutrient Levels

AimsBacillus, a gram-positive bacterium, has multiple beneficial traits which help the plants in nutrients acquisition, either directly or indirectly. However, the mechanisms that mediate the positive or negative impact of Bacillus on exotic or native species are poorly understood. Our objective was to determine whether the quantitative and/ or qualitative differences in the Bacillus community present on the exotic Ambrosia artemisiifolia and the native Setaria viridis provide a competitive advantage to the invader over native species. MethodsA. artemisiifolia monoculture, mixture of A. artemisiifolia and S. viridis and S. viridis monoculture were designed in the field experiment. Bacillus diversity in their rhizospheres was analyzed using 16S rRNA and their effects on the competitive growth of A. artemisiifolia and S. viridis were tested in greenhouse experiment.ResultsThe Shannon index, species richness, and evenness index of Bacillus diversity in the rhizosphere soil of A. artemisiifolia in the monoculture treatment were lower than in the mixture treatment. The relative abundance of Bacillus megaterium in the rhizosphere soil of A. artemisiifolia was higher than that in the rhizosphere soil of S. viridis. Whether Bacillus in the rhizosphere soil of A. artemisiifolia or B. megaterium inoculation enhanced the relative competitiveness of A. artemisiifolia and inhibited that of S. viridis by altering their carbon, nitrogen, and phosphorus concentrations. ConclusionsA. artemisiifolia invasion influenced Bacillus communities, especially B. megaterium. The higher abundance of B. megaterium in A. artemisiifolia rhizosphere creates higher levels of the available nutrient than that in native S. viridis.