The nanotechnology among US: are metal and metal oxides nanoparticles a nano or mega risk for soil microbial communities?

Metal nanoparticles and metal oxides nanoparticles (MNPs/MONPs) have been widely included in a great diversity of products and industrial applications and they are already a part of our everyday life. According to estimation studies, their production is expected to increase exponentially in the next few years. Consequently, soil has been suggested as the main sink of MNPs/MONPs once they are deliberately or accidentally released into the environment. The potential negative perturbations that may result on soil microbial communities and ecological processes are resulting in concerns. Several nano-toxicological studies of MNPs/MONPs, reported so far, have focused on aquatic organisms, animals, and soil invertebrates. However, during recent years, the studies have been oriented to understand the effects of MNPs/MONPs on microbial communities and their interaction with soil components. The studies have suggested that MNPs/MONPs are one of the most toxic type to soil biota, amongst different types of nanomaterials. This may threaten soil health and fertility, since microbial communities are known to support important biological processes and ecosystem services such as the nutrient cycling, whereby their protection against the environmental pollution is imperative. Therefore, in this review we summarize the actual knowledge available from the last five years (2013–2018) and gaps about the potential negative, positive or neutral effects produced on soil by different classes of MNPs/MONPs. A particular emphasis has been placed on the associated soil microorganisms and biological processes. Finally, perspectives about future research are discussed.     

Fungal volatiles: an environmentally friendly tool to control pathogenic microorganisms in plants

Fungi are an extraordinary and immensely diverse group of microorganisms that colonize many habitats even competing with other microorganisms. Fungi have received recognition for interesting metabolic activities that have an enormous variety of biotechnological applications. Previously, volatile organic compounds produced by fungi (FVOCs) have been demonstrated to have a great capacity for use as antagonist products against plant pathogens. However, in recent years, FVOCs have been received attention as potential alternatives to the use of traditional pesticides and, therefore, as important eco-friendly biotechnological tools to control plant pathogens. Therefore, highlighting the current state of knowledge of these fascinating FVOCs, the actual detection techniques and the bioactivity against plant pathogens is essential to the discovery of new products that can be used as biopesticides.     

Timing of fission in the starfish Allostichaster capensis (Echinodermata: Asteroidea) in laboratory

Timing of fission in the fissiparous starfish Allostichaster capensis under laboratory conditions is described. A. capensis generally splits across the disc along the fission plane during the spring, and then each half regenerates the missing arms during the rest of the year. The fission process can last eight hours. The healing process starts immediately after fission. A. capensis has impressive regeneration ability, including a comet, without signs of disc, regenerated two new arms.     

Nutrient allocation in the gonads of the sea urchin Arbacia dufresnii in different stages of gonadal development

This study reports nutrient allocation in different stages of gonadal development for two populations of the sea urchin Arbacia dufresnii off the Patagonian coast of Argentina (Nuevo Gulf and San Jorge Gulf). The biochemical composition of gonads was used to assess nutrient allocation by measuring ash, soluble protein, lipid and trichloroacetic acid-soluble carbohydrate concentrations, and absolute contents over a 24-month period. Reproductive output in terms of energy was calculated for females. Results were correlated with histological stage of the gonads. Soluble proteins were the main component for the Nuevo Gulf population while unmeasured organic material (i.e. insoluble proteins and nucleic acids, especially in testes) was prevalent in gonads from San Jorge Gulf. Soluble protein and lipid concentrations followed the gonadal cycle, while carbohydrate concentration was almost negligible, especially in the Nuevo Gulf population. The different patterns in the gonadal cycle in the two populations were reflected in the biochemical composition of gonads. Concentrations and contents of the biochemical components and reproductive output were higher in the population from San Jorge Gulf owing to the larger size of gonads and gametes. These findings contribute to the better understanding of the plasticity of the reproductive biology of A. dufresnii in different environments.     

Bioremediation of a Chilean Andisol contaminated with pentachlorophenol (PCP) by solid substrate cultures of white-rot fungi

This study provides a first attempt investigation of a serie of studies on the ability of Anthracophyllum discolor, a recently isolated white-rot fungus from forest of southern Chile, for the treatment of soil contaminated with pentachlorophenol (PCP) to future research on potential applications in bioremediation process. Bioremediation of soil contaminated with PCP (250 and 350 mg kg⁻¹ soil) was investigated with A. discolor and compared with the reference strain Phanerochaete chrysosporium. Both strains were incorporated as free and immobilized in wheat grains, a lignocellulosic material previously selected among wheat straw, wheat grains and wood chips through the growth and colonization of A. discolor. Wheat grains showed a higher growth and colonization of A. discolor, increasing the production of manganese peroxidase (MnP) activity. Moreover, the application of white-rot fungi immobilized in wheat grains to the contaminated soil favored the fungus spread. In turn, with both fungal strains and at the two PCP concentrations a high PCP removal (70–85%) occurred as respect to that measured with the fungus as free mycelium (30–45%). Additionally, the use of wheat grains in soil allowed the proliferation of microorganisms PCP decomposers, showing a synergistic effect with A. discolor and P. chrysosporium and increasing the PCP removal in the soil.     

Pesticide dissipation and microbial community changes in a biopurification system: influence of the rhizosphere

The dissipation of atrazine, chlorpyrifos and iprodione in a biopurification system and changes in the microbial and some biological parameters influenced by the rhizosphere of Lolium perenne were studied in a column system packed with an organic biomixture. Three column depths were analyzed for residual pesticides, peroxidase, fluorescein diacetate activity and microbial communities. Fungal colonization was analyzed by confocal laser scanning microscopy to assess the extent of its proliferation in wheat straw. The L. perenne rhizosphere enhanced pesticide dissipation and negligible pesticide residues were detected at 20–30 cm column depth. Atrazine, chlorpyrifos and iprodione removal was 82, 89 and 74% respectively in the first 10 cm depth for columns with vegetal cover. The presence of L. perenne in contaminated columns stimulated peroxidase activity in all three column depth sections. Fluorescein diacetate activity decreased over time in all column sections with the highest values in biomixtures with vegetal cover. Microbial communities, analyzed by PCR-DGGE, were not affected by the pesticide mixture application, presenting high values of similarity (>65%) with and without vegetal cover. Microbial abundance of Actinobacteria varied according to treatment and no clear link was observed. However, bacterial abundance increased over time and was similar with and without vegetal cover. On the other hand, fungal abundance decreased in all sections of columns after 40 days, but an increase was observed in response to pesticide application. Fungal colonization and straw degradation during pesticide dissipation were verified by monitoring the lignin autofluorescence loss.     

Contrasting responses of cluster roots formation induced by phosphorus and nitrogen supply in Embothrium coccineum populations from different geographical origin

Plant and Soil - Embothrium coccineum is a pioneer tree that produces cluster roots (CR) induced by phosphorus (P) or nitrogen (N) deficiency, but the role which both N and P play in CR formation...