Effects of the biogenic gold nanoparticles on microbial community structure and activities

Metal nanoparticles and pesticides under global climate change: Assessing the combined effects of multiple abiotic stressors on soil microbial ecosystems

The soil is a vital resource that hosts many microorganisms crucial in biogeochemical cycles and ecosystem health. However, human activities such as the use of metal nanoparticles (MNPs), pesticides and the impacts of global climate change (GCCh) can significantly affect soil microbial communities (SMC). For many years, pesticides and, more recently, nanoparticles have contributed to sustainable agriculture to ensure continuous food production to sustain the significant growth of the world population and, therefore, the demand for food. Pesticides have a recognized pest control capacity. On the other hand, nanoparticles have demonstrated a high ability to improve water and nutrient retention, promote plant growth, and control pests. However, it has been reported that their accumulation in agricultural soils can also adversely affect the environment and soil microbial health. In addition, climate change, with its variations in temperature and extreme water conditions, can lead to drought and increased soil salinity, modifying both soil conditions and the composition and function of microbial communities. Abiotic stressors can interact and synergistically or additively affect soil microorganisms, significantly impacting soil functioning and the capacity to provide ecosystem services. Therefore, this work reviewed the current scientific literature to understand how multiple stressors interact and affect the SMC. In addition, the importance of molecular tools such as metagenomics, metatranscriptomics, proteomics, or metabolomics in the study of the responses of SMC to exposure to multiple abiotic stressors was examined. Future research directions were also proposed, focusing on exploring the complex interactions between stressors and their long-term effects and developing strategies for sustainable soil management. These efforts will contribute to the preservation of soil health and the promotion of sustainable agricultural practices.

Effects of Gold Nanoparticles on Mentha spicata L., Soil Microbiota, and Human Health Risks: Impact of Exposure Routes

Nanoparticles, due to their extensive production and application, can have significant consequences for the environment, including soil and plant pollution. Therefore, it is very important to assess how nanoparticles will affect plants depending on the exposure pathways. The effect of gold nanoparticles in a concentration range of 1-100 mg/L on Mentha spicata L. during a 28-day experiment was investigated. Two routes of nanoparticles exposure were applied: root and foliar. Transmission electron microscopy was used to characterize nanoparticles and their effect on plant leaves' ultrastructure. Gold content in soil and plant segments was determined using k0-neutron activation analysis. For root exposure, gold was mainly accumulated in soil (15.2-1769 mg/kg) followed by root systems (2.99-454 mg/kg). The maximum accumulation of gold in leaves (5.49 mg/kg) was attained at a nanoparticle concentration of 100 mg/L. Foliar exposure resulted in the maximum uptake of gold in leaves (552 mg/kg) and stems (18.4 mg/kg) at the highest applied nanoparticle concentration. The effect of nanoparticles on the Mentha spicata L. leaves' biochemical composition was assessed. Nanoparticles affected the content of chlorophyll and carotenoids and led to an increase in antioxidant activity. Root exposure to gold nanoparticles resulted in an increase in the number of starch grains in chloroplasts and also suppressed the activity of the soil microbiota. Gold extraction from mint leaves into herbal infusion varied from 2 to 90% depending on the concentration of nanoparticles in the solution and the exposure route. The health risk as a result of gold exposure via herbal tea intake was assessed through estimated daily intake. The hazard quotient values were found to be less than the cutoff, indicating that a cup of tea infusion should not cause a serious impact to human health.

Comparative Effect of Commercially Available Nanoparticles on Soil Bacterial Community and “Botrytis fabae” Caused Brown Spot: In vitro and in vivo Experiment

This study revealed the possible effects of various levels of silver nanoparticle (AgNP) application on plant diseases and soil microbial diversity. It investigated the comparison between the application of AgNPs and two commercial nanoproducts (Zn and FeNPs) on the rhizobacterial population and Botrytis fabae. Two experiments were conducted. The first studied the influence of 13 AgNP concentration on soil bacterial diversity besides two other commercial nanoparticles, ZnNPs (2,000 ppm) and FeNPs (2,500 ppm), used for comparison and application on onion seedlings. The second experiment was designed to determine the antifungal activity of previous AgNP concentrations (150, 200, 250, 300, 400, and 500 ppm) against B. fabae, tested using commercial fungicide as control. The results obtained from both experiments revealed the positive impact of AgNPs on the microbial community, representing a decrease in both the soil microbial biomass and the growth of brown spot disease, affecting microbial community composition, including bacteria, fungi, and biological varieties. In contrast, the two commercial products displayed lower effects compared to AgNPs. This result clearly showed that the AgNPs strongly inhibited the plant pathogen B. fabae growth and development, decreasing the number of bacteria (cfu/ml) and reducing the rhizosphere. Using AgNPs as an antimicrobial agent in the agricultural domain is recommended.

Nanopharmaceuticals (Au-NPs) after use: Experiences with a complex higher tier test design simulating environmental fate and effect

The current environmental hazard assessment is based on the testing of the pristine substance. However, it cannot be excluded that (nano)pharmaceuticals are excreted into sewage during the use phase followed by entry into wastewater treatment plants (WWTPs). Sorption to sewage sludge or release via effluent can result in modified ecotoxicological effects which possibly can only be detected with a modified test approach. The objective of our study was to investigate a realistic exposure scenario for metallic nanoparticles (NPs) in pharmaceutical products, excreted into effluent, and released into the environment after treatment in WWTPs. The test approach was illustrated by using gold (Au) NPs. Effluent from model WWTPs were investigated in aquatic tests (Daphnia magna, fish cell lines). Sewage sludge was used as a sole food source (Eisenia fetida) or mixed with soil and used as test medium (soil microorganisms, Folsomia candida, Enchytraeus crypticus). To cover the aspect of regulation, the test systems described in OECD-test guidelines (OECD TG 201, 211, 220, 232, 249, 317) were applied. Modifications and additional test approaches were included to meet the needs arising out of the testing of nanomaterials and of the exposure scenarios. The results were assessed regarding the suitability of the test design and the toxicity of Au-NPs. Except for activated sludge as a sole food source for E.fetida, the selected test approach is suitable for the testing of nanomaterials. Additional information can be gained when compared to the common testing of the pristine nanomaterials in the standardized test systems. Effects of Au-NPs were observed in concentrations exceeding the modeled environmental.

Overview of microbes based fabricated biogenic nanoparticles for water and wastewater treatment

Treatment of toxic and emerging pollutants (T&EPs) is increasing the threats to the survival of conventional wastewater treatment (WWTs) technologies. The high installation and operational costs of advanced treatment technologies have shifted the research interest to the development of economical and reliable technology for management of T&EPs. Thus, recently biogenic nanoparticles (BNPs) fabricated using microbes/microorganisms are getting tremendous research interest due to their unique properties (i.e. high specific surface area, desired morphology, catalytic reactivity) for the biodegradation and biosorption of T&EPs. In addition, BNPs can be manufactured using metal contaminated water which indicates a hidden potential for resource recovery and utilization. Therefore, the present study discusses the adsorptive and catalytic performance of BNPs in the removal of T&EPs from water (W) and wastewater (WW). In addition, inspired by the superior performance of BNPs in advance WWT, a model of BNPs based WWT resource recovery and utilization process is also proposed. Finally, main issues i.e. mass production, leaching, poisoning/toxicity, regeneration, reusability and fabrication costs and process optimization are discussed which are main hinders in the transfer of BNPs based WWT technologies from laboratory to commercial scale.

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.

Effect of biosynthesized silver nanoparticles on native soil microflora via plant transport during plant-pathogen-nanoparticles interaction

In this study, the interaction of biosynthesized silver nanoparticles (BSNP) with native soil via plant transport was assessed in model pathosystem of Arabidopsis thaliana and Alternaria brassicicola. Foliar application of 5 μg/mL of BSNP reduced number of spores of fungi to 2.2 × 10⁵ from 7 × 10⁵, while numbers of lesions got reduced to 0.9/leaf in treated plants compared to 2.9/leaf in pathogen-infected plant without altering soil pH, electric conductivity, soil organic carbon and soil microbial biomass carbon. Soil enzyme activities including dehydrogenase, acid and alkaline phosphatase, urease, β-glucosidase and protease did not alter significantly in BSNP-treated plants compared to control plants. Application of BSNP did not alter the number of cultivable bacteria, fungi and actinomycetes. Effect of BSNP on uncultured bacterial diversity was measured by DGGE analysis which revealed similar banding pattern in all different treatments except in A. brassicicola-infected (AB) and A. brassicicola-infected plants treated with silver nanoparticles (AB + BSNP) after 120 days. Although AB-infected plants exhibited a decrease in bacterial diversity, treatment of AB + BSNP after 120 days demonstrated maximum bacterial diversity. McIntosh, Shannon, and Simpson diversity indices were calculated based on carbon source utilization pattern by BIOLOG analysis, revealing no significant difference among all treatments in different time intervals. BSNPs have the potential to act as strong antimicrobial agent for plant disease management without altering the native soil microflora.

Nanosized Drug Delivery Systems in Gastrointestinal Targeting: Interactions with Microbiota

The new age of nanotechnology has signaled a stream of entrepreneurial possibilities in various areas, form industry to medicine. Drug delivery has benefited the most by introducing nanostructured systems in the transport and controlled release of therapeutic molecules at targeted sites associated with a particular disease. As many nanosized particles reach the gastrointestinal tract by various means, their interactions with the molecular components of this highly active niche are intensively investigated. The well-characterized antimicrobial activities of numerous nanoparticles are currently being considered as a reliable and efficient alternative to the eminent world crisis in antimicrobial drug discovery. The interactions of nanosystems present in the gastrointestinal route with host microbiota is unavoidable; hence, a major research initiative is needed to explore the mechanisms and effects of these nanomaterials on microbiota and the impact that microbiota may have in the outcome of therapies entailing drug delivery nanosystems through the gastrointestinal route. These coordinated studies will provide novel techniques to replace or act synergistically with current technologies and help develop new treatments for major diseases via the discovery of unique antimicrobial molecules.