Contrasting response of two forest soils to nitrogen input: rapidly altered NO and N2O emissions and nirK abundance

Denitrification represents one of the main microbial processes producing the primary and secondary greenhouse gases nitrous oxide (N₂O) and nitric oxide (NO) in soils. It is well established that abiotic factors like the soil water content and the availability of nitrogen (N) are key parameters determining the activity of denitrifiers in soils. However, soils differing regarding their characteristics such as the content of C_org, the soil texture or the pH value may respond in specific manners to equivalent changes in soil moisture and N input. Thus, short-term incubation experiments were performed to test and compare the capacity of two contrasting Austrian forest soils to respond to mineral N application at increased soil water contents. Soils from the pristine Rothwald forest (rich in C_org) and the more acidic Schottenwald forest (poor in C_org) were amended with either NH ₄ ⁺ -N or NO ₃ ^? -N and were incubated at 40% and 70% water-filled pore space for 4 days. Changes in mineral N pools, nitrite reductase activity and NO and N₂O emission rates were measured, and the abundance and structural community composition of the functional group involved in nitrite reduction were analysed via quantitative real-time polymerase chain reaction and terminal restriction fragment length polymorphism analysis of the nirK gene. Rapid and distinct activity responses to increased soil moisture and altered mineral nitrogen availability were observed in two contrasting forest soils. In both soils, nitrogen oxide emission rates were stimulated by N inputs and, depending on the soil moisture status, either NO or N₂O emission was prevailing. However, different N cycling processes appeared to predominate in either soil under equivalent treatment. Nitrogen oxide emissions peaked following NO ₃ ^? application in Schottenwald soils but were the highest after NH ₄ ⁺ application in Rothwald soils. Denitrifying (nirK) communities differed significantly in Rothwald and Schottenwald soils; however, changes in the community structure were marginal during the short-term incubation. Abundances of nirK genes remained unaffected by N application in either soil. The soil water content affected nirK gene abundances only in Rothwald soil, indicating a distinct reaction of nitrite reducing communities in the two soils.     

Application of denaturing high-performance liquid chromatography (DHPLC) for the identification of fish: a new way to determine the composition of processed food containing multiple species

The identification of fish species in transformed food products is difficult because the existing methods are not adapted to heat-processed products containing more than one species. Using a common to all vertebrates region of the cytochrome b gene, we have developed a denaturing high-performance liquid chromatography (DHPLC) fingerprinting method, which allowed us to identify most of the species in commercial crab sticks. Whole fish and fillets were used for the creation of a library of referent DHPLC profiles. Crab sticks generated complex DHPLC profiles in which the number of contained fish species can be estimated by the number of major fluorescence peaks. The identity of some of the species was predicted by comparison of the peaks with the referent profiles, and others were identified after collection of the peak fractions, reamplification, and sequencing. DHPLC appears to be a quick and efficient method to analyze the species composition of complex heat-processed fish products.     

Fitness costs associated with infections of secondary endosymbionts in the cassava whitefly species <Emphasis Type="Italic">Bemisia tabaci</Emphasis>

We investigated the dual effects of bacterial infections and diseased cassava plants on the fitness and biology of the Bemisia tabaci infesting cassava in Africa. Isofemale B. tabaci colonies of sub-Saharan Africa 1-subgroup 3 (SSA1-SG3), infected with two secondary endosymbiotic bacteria Arsenophonus and Rickettsia (AR+) and those free of AR infections (AR?), were compared for fitness parameters on healthy and East African cassava mosaic virus-Uganda variant (EACMV-UG)-infected cassava plants. The whitefly fecundity and nymph development was not affected by bacterial infections or the infection of cassava by the virus. However, emergence of adults from nymphs was 50 and 17% higher by AR? on healthy and virus-infected plants, respectively, than AR+ flies. Development time of adults also was 10 days longer in AR+ than AR?. The whiteflies were further compared for acquisition and retention of EACMV-UG. Higher proportion of AR? acquired (91.8%) and retained (87.6%) the virus than AR+ (71.8, 61.2%, respectively). Similarly, the AR? flies retained higher quantities of virus (~ninefold more) than AR+. These results indicated that bacteria-free whiteflies were superior and better transmitters of EACMV-UG, as they had higher adult emergence, quicker life cycle and better virus retention abilities than those infected with bacteria.     

Post‐anesthetic pulmonary edema in two horses

Case 1 A two‐year old, 462 kg Standard bred horse was anesthetized for arthroscopy and castration. During anesthesia, hyperemia of the mucosal membranes and urticaria were noticed. During 5 hours of anesthesia subcutaneous edema of the eyelids and neck region developed. In the recovery box, the orotracheal (OT) tube was left in situ and secured in place with tape. Following initial attempts to stand, the horse became highly agitated and signs consistent with pulmonary edema developed subsequently. Arterial hypoxemia (PaO₂: 3.7 kPa [28 mmHg]) and hypocapnia (PaCO₂: 3.1 kPa [23 mmHg]) were confirmed. Oxygen and furosemide were administered. The horse was assisted to standing with a sling. Therapy continued with bilateral intra‐nasal oxygen insufflation. Ancillary medical therapy included flunixin meglumine, penicillin, gentamycin and dimethylsulfoxide. Following 7 hours of treatment the arterial oxygen tensions began to increase towards normal values. Case 2 An 11‐year old, 528 kg Paint horse was anesthetized for surgery of a submandibular mass. The 4‐hour anesthetic period was unremarkable. The OT tube was left in situ for the recovery. During recovery, the horse was slightly agitated and stood after three attempts. Clinical signs consistent with pulmonary edema and arterial hypoxemia (PaO₂: 5 kPa [37.5 mmHg]) subsequently developed following extubation. Respiratory signs resolved with medical therapy, including unilateral nasal oxygen insufflation, furosemide, flunixin meglumine and dimethylsulfoxide. The diagnosis of pulmonary edema in these horses was made by clinical signs and arterial blood‐gas analysis. While pulmonary radiographs were not taken to confirm the diagnosis, the clinical signs following anesthesia support the diagnosis in both cases. The etiology of pulmonary edema was most likely multifactorial.     

Hunt for Palytoxins in a Wide Variety of Marine Organisms Harvested in 2010 on the French Mediterranean Coast

During the summer of 2010, 31 species including fish, echinoderms, gastropods, crustaceans, cephalopods and sponges were sampled in the Bay of Villefranche on the French Mediterranean coast and screened for the presence of PLTX-group toxins using the haemolytic assay. Liquid chromatography tandem mass spectrometry (LC-MS/MS) was used for confirmatory purposes and to determine the toxin profile. The mean toxin concentration in the whole flesh of all sampled marine organisms, determined using the lower- (LB) and upper-bound (UB) approach was 4.3 and 5.1 µg·kg⁻¹, respectively, with less than 1% of the results exceeding the European Food Safety Authority (EFSA) threshold of 30 µg·kg⁻¹ and the highest values being reported for sea urchins (107.6 and 108.0 µg·kg⁻¹). Toxins accumulated almost exclusively in the digestive tube of the tested species, with the exception of octopus, in which there were detectable toxin amounts in the remaining tissues (RT). The mean toxin concentration in the RT of the sampled organisms (fishes, echinoderms and cephalopods) was 0.7 and 1.7 µg·kg⁻¹ (LB and UB, respectively), with a maximum value of 19.9 µg·kg⁻¹ for octopus RT. The herbivorous and omnivorous organisms were the most contaminated species, indicating that diet influences the contamination process, and the LC-MS/MS revealed that ovatoxin-a was the only toxin detected.     

Low-Molecular-Weight Fucoidan Induces Endothelial Cell Migration via the PI3K/AKT Pathway and Modulates the Transcription of Genes Involved in Angiogenesis

Low-molecular-weight fucoidan (LMWF) is a sulfated polysaccharide extracted from brown seaweed that presents antithrombotic and pro-angiogenic properties. However, its mechanism of action is not well-characterized. Here, we studied the effects of LMWF on cell signaling and whole genome expression in human umbilical vein endothelial cells and endothelial colony forming cells. We observed that LMWF and vascular endothelial growth factor had synergistic effects on cell signaling, and more interestingly that LMWF by itself, in the absence of other growth factors, was able to trigger the activation of the PI3K/AKT pathway, which plays a crucial role in angiogenesis and vasculogenesis. We also observed that the effects of LMWF on cell migration were PI3K/AKT-dependent and that LMWF modulated the expression of genes involved at different levels of the neovessel formation process, such as cell migration and cytoskeleton organization, cell mobilization and homing. This provides a better understanding of LMWF’s mechanism of action and confirms that it could be an interesting therapeutic approach for vascular repair.     

Silage additives to reduce protein degradation during ensiling and evaluation of in vitro ruminal nitrogen degradability

Despite the high degradability of their proteins, grass and legume silages represent an important option to reach more sustainable livestock systems. To improve the nitrogen use efficiency of these crops, this study assessed the potential of several additives (chestnut tannins, oak tannins, zeolite, erythritol by‐product solution and wood molasses) to reduce proteolysis in the silo and in vitro nitrogen degradability. Ryegrass (Lolium multiflorum) and red clover (Trifolium pratense) were ensiled in varying proportions in laboratory‐scale silos made of vacuum‐packed plastic bags. Dry‐matter content, chemical composition, pH, ammonia and volatile fatty acids content were analysed after 34 days of ensiling. Ruminal nitrogen degradability was assessed in vitro (Aufrère & Cartailler, 1988 ). We observed that the proportion of ammonia in silage was reduced by the addition of oak tannin (?12%) and zeolite (?16%). The addition of zeolite lowered in vitro organic matter digestibility. Rapidly degradable nitrogen (1‐hr degradability) was reduced in vitro by both tannins (?6.8% for chestnut and ?6.6% for oak) and zeolite (?5.8%), but total degradable nitrogen (24‐hr degradability) was only reduced by oak (?6.5%) and chestnut tannins (?7.3%). It suggests that tannins protected proteins from plant and bacterial enzymes by forming a complex that better resists silage fermentations and in vitro protease action. The reduction effects on proteolysis in the silo and on in vitro ruminal nitrogen degradability are limited individually but could be cumulative. Erythritol by‐product solution and wood molasses had no effect on silo or in vitro proteolysis.     

Effect of Geogenic Lead on Fungal and Collembolan Communities in Garden Topsoil

Geogenic lead (Pb) is considered to be less bioavailable than anthropogenic Pb and exerts less effect on the soil fauna. However, Pb contamination in vegetables has been reported in the case of geogenic anomalies, even at moderate concentrations (around 170 mg kg^–1). In this study, we investigated collembolan communities using both taxonomic- and trait-based approaches and observed fungal communities to assess the effects of a moderate geogenic Pb anomaly on collembolans and fungi in an urban vegetable garden soil. Results indicated that geogenic Pb indeed modified fungi communities and altered the functional structure of collembolan communities in garden soils. Although geogenic Pb presented low bioavailability, it affected soil fauna and vegetables similar to anthropogenic Pb.