Heavy metals concentration in soils across the conterminous USA: Spatial prediction, model uncertainty, and influencing factors.

Assessment and proper management of sites contaminated with heavy metals require precise information on the spatial distribution of these metals. This study aimed to predict and map the distribution of Cd, Cu, Ni, Pb, and Zn across the conterminous USA using point observations, environmental variables, and Histogram-based Gradient Boosting (HGB) modeling. Over 9180 surficial soil observations from the Soil Geochemistry Spatial Database (SGSD) (n = 1150), the Geochemical and Mineralogical Survey of Soils (GMSS) (n = 4857), and the Holmgren Dataset (HD) (n = 3400), and 28 covariates (100 m × 100 m grid) representing climate, topography, vegetation, soils, and anthropic activity were compiled. Model performance was evaluated on 20 % of the data not used in calibration using the coefficient of determination (R2), concordance correlation coefficient (ρc), and root mean square error (RMSE) indices. Uncertainty of predictions was calculated as the difference between the estimated 95 and 5 % quantiles provided by HGB. The model explained up to 50 % of the variance in the data with RMSE ranging between 0.16 (mg kg-1) for Cu and 23.4 (mg kg-1) for Zn, respectively. Likewise, ρc ranged between 0.55 (Cu) and 0.68 (Zn), respectively, and Zn had the highest R2 (0.50) among all predictions. We observed high Pb concentrations near urban areas. Peak concentrations of all studied metals were found in the Lower Mississippi River Valley. Cu, Ni, and Zn concentrations were higher on the West Coast; Cd concentrations were higher in the central USA. Clay, pH, potential evapotranspiration, temperature, and precipitation were among the model's top five important covariates for spatial predictions of heavy metals. The combined use of point observations and environmental covariates coupled with machine learning provided a reliable prediction of heavy metals distribution in the soils of the conterminous USA. The updated maps could support environmental assessments, monitoring, and decision-making with this methodology applicable to other soil databases, worldwide.

Microbiological Indicators of Soil Quality Under Native Forests are Influenced by Topographic Factors.

Several microbiological indicators of soil quality present high sensitivity, but little is known about the influence of topographic factors on them. This work aimed to evaluate variability of biological indicators of soil quality across a hillslope under native forest and the influence of topographic factors on them. Four positions on a hillslope were evaluated. Activity of the enzymes ß-glucosidase, acid phosphatase, urease and fluorescein diacetate (FDA) hydrolysis were determined, as well as basal and substrate-induced respiration, and density of microorganisms: total bacteria, total fungi, actinobacteria, phosphate solubilizers, ammonifiers, native rhizobia, free-living N2-fixing bacteria, spores of arbuscular mycorrhizal fungi and percentage of root colonization by arbuscular mycorrhizal fungi. Activity and density of microorganisms were correlated with topographic factors. The relation of these factors to the variations of the evaluated indicators was determined using the random forest algorithm. Microbiological indicators varied according to the hillslope positions. The indicators urease, basal respiration, spore density, mycorrhizal colonization, total bacteria and fungi, phosphate solubilizers, and free-living N2-fixing bacteria detected in JNFB and FAM culture medium did not vary with terrain attributes and were therefore more indicated in cases of topographic variations. This and future studies can help to select the best microbiological indicators for different conditions.

Investigation on the 19S ATPase proteasome subunits (Rpt1-6) conservation and their differential gene expression in Schistosoma mansoni.

The ubiquitin-proteasome system is responsible for degradation of the majority of intracellular proteins in eukaryotic cells. The 26S proteasome proteolytic complex is composed of a 20S core particle responsible for protein degradation and the 19S lid which plays a role in the recognition of polyubiquitinated substrates. The 19S regulatory particle (Rps) is composed of ATPase (Rpt) and non-ATPase (Rpn) subunits. In this study, we analyzed the expression profile of 19S Rpt subunits in the larvae and adult stage of the Schistosoma mansoni life cycle. Conventional reverse transcriptase polymerase chain reaction (RT-PCR) revealed that the majority of the 19S Rpt subunits amplified at the expected molecular masses for various investigated stages. In addition, SmRpt1, SmRpt2, and SmRpt6 transcript levels were increased in 3 h-cultured schistosomula and reasonably maintained until 5 h in culture, as revealed by qRT-PCR. Phylogenetic analysis of 19S Rpt subunits showed high structural conservation in comparison to other Rpt orthologues. The mRNA expression profile of 19S Rpt subunits did not correlate with 26S proteasome proteolytic activity as judged by a (14)C-casein-degrading assay, in the early cultured schistosomula. Taken together, these results revealed a differential expression profile for 19S Rpt subunits whose transcript levels could not be directly associated to 26S proteasome activity.

How much is too little to detect impacts? A case study of a nuclear power plant.

Several approaches have been proposed to assess impacts on natural assemblages. Ideally, the potentially impacted site and multiple reference sites are sampled through time, before and after the impact. Often, however, the lack of information regarding the potential overall impact, the lack of knowledge about the environment in many regions worldwide, budgets constraints and the increasing dimensions of human activities compromise the reliability of the impact assessment. We evaluated the impact, if any, and its extent of a nuclear power plant effluent on sessile epibiota assemblages using a suitable and feasible sampling design with no 'before' data and budget and logistic constraints. Assemblages were sampled at multiple times and at increasing distances from the point of the discharge of the effluent. There was a clear and localized effect of the power plant effluent (up to 100 m from the point of the discharge). However, depending on the time of the year, the impact reaches up to 600 m. We found a significantly lower richness of taxa in the Effluent site when compared to other sites. Furthermore, at all times, the variability of assemblages near the discharge was also smaller than in other sites. Although the sampling design used here (in particular the number of replicates) did not allow an unambiguously evaluation of the full extent of the impact in relation to its intensity and temporal variability, the multiple temporal and spatial scales used allowed the detection of some differences in the intensity of the impact, depending on the time of sampling. Our findings greatly contribute to increase the knowledge on the effects of multiple stressors caused by the effluent of a power plant and also have important implications for management strategies and conservation ecology, in general.

A proteomic approach to identifying proteins differentially expressed in conidia and mycelium of the entomopathogenic fungus Metarhizium acridum.

Metarhizium spp. is an important worldwide group of entomopathogenic fungi used as an interesting alternative to chemical insecticides in programs of agricultural pest and disease vector control. Metarhizium conidia are important in fungal propagation and also are responsible for host infection. Despite their importance, several aspects of conidial biology, including their proteome, are still unknown. We have established conidial and mycelial proteome reference maps for Metarhizium acridum using two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF MS). In all, 1130±102 and 1200±97 protein spots were detected in ungerminated conidia and fast-growing mycelia, respectively. Comparison of the two protein-expression profiles reveled that only 35% of the protein spots were common to both developmental stages. Out of 94 2-DE protein spots (65 from conidia, 25 from mycelia and two common to both) analyzed using mass spectrometry, seven proteins from conidia, 15 from mycelia and one common to both stages were identified. The identified protein spots exclusive to conidia contained sequences similar to known fungal stress-protector proteins (such as heat shock proteins (HSP) and 6-phosphogluconate dehydrogenase) plus the fungal allergen Alt a 7, actin and the enzyme cobalamin-independent methionine synthase. The identified protein spots exclusive to mycelia included proteins involved in several cell housekeeping biological processes. Three proteins (HSP 90, 6-phosphogluconate dehydrogenase and allergen Alt a 7) were present in spots in conidial and mycelial gels, but they differed in their locations on the two gels.

Quantification of cyclobutane pyrimidine dimers induced by UVB radiation in conidia of the fungi Aspergillus fumigatus, Aspergillus nidulans, Metarhizium acridum and Metarhizium robertsii.

Conidia are responsible for reproduction, dispersal, environmental persistence and host infection of many fungal species. One of the main environmental factors that can kill and/or damage conidia is solar UV radiation. Cyclobutane pyrimidine dimers (CPD) are the major DNA photoproducts induced by UVB. We examined the conidial germination kinetics and the occurrence of CPD in DNA of conidia exposed to different doses of UVB radiation. Conidia of Aspergillus fumigatus, Aspergillus nidulans and Metarhizium acridum were exposed to UVB doses of 0.9, 1.8, 3.6 and 5.4 kJ m(-2). CPD were quantified using T4 endonuclease V and alkaline agarose gel electrophoresis. Most of the doses were sublethal for all three species. Exposures to UVB delayed conidial germination and the delays were directly related both to UVB doses and CPD frequencies. The frequencies of dimers also were linear and directly proportional to the UVB doses, but the CPD yields differed among species. We also evaluated the impact of conidial pigmentation on germination and CPD induction on Metarhizium robertsii. The frequency of dimers in an albino mutant was approximately 10 times higher than of its green wild-type parent strain after exposure to a sublethal dose (1.8 kJ m(-2)) of UVB radiation.

Photodynamic inactivation of conidia of the fungi Metarhizium anisopliae and Aspergillus nidulans with methylene blue and toluidine blue.

Antimicrobial photodynamic treatment (PDT) is a promising method that can be used to control localized mycoses or kill fungi in the environment. A major objective of the current study was to compare the conidial photosensitization of two fungal species (Metarhizium anisopliae and Aspergillus nidulans) with methylene blue (MB) and toluidine blue (TBO) under different incubation and light conditions. Parameters examined were media, photosensitizer (PS) concentration and light source. PDT with MB and TBO resulted in an incomplete inactivation of the conidia of both fungal species. Conidial inactivation reached up to 99.7%, but none of the treatments was sufficient to achieve a 100% fungicidal effect using either MB or TBO. PDT delayed the germination of the surviving conidia. Washing the conidia to remove unbound PS before light exposure drastically reduced the photosensitization of A. nidulans. The reduction was much smaller in M. anisopliae conidia, indicating that the conidia of the two species interact differently with MB and TBO. Conidia of green and yellow M. anisopliae mutants were less affected by PDT than mutants with white and violet conidia. In contrast to what occurred in PBS, photosensitization of M. anisopliae and A. nidulans conidia was not observed when PDT was performed in potato dextrose media.

Schistosoma mansoni: gene expression of the nucleotide excision repair factor 2 (NEF2) during the parasite life cycle, and in adult worms after exposure to different DNA-damaging agents.

DNA is often damaged by many environmental agents, which lead to the up-regulation of several genes involved in different repair pathways. Schistosoma mansoni has a complex life cycle, being exposed to a subset of DNA-damaging agents, such as those present in the environment and host immune response. Recently, studies showed that nucleotide excision repair (NER) is an indispensable mechanism for removing a broad spectrum of different DNA lesions. In the present report, we showed the gene expression of nucleotide excision repair factor 2 (NEF2) SmRad23 and SmRad4, in different developmental stages of S. mansoni, as well as the differential expression of these genes in S. mansoni adult worms treated with DNA-damaging agents. Furthermore, it was revealed the correlation of these genes with their orthologues in other eukaryotes. Our reports suggest that NER is an important repair pathway during the complex life cycle of S. mansoni.