Toxicity Evaluation of Chlorpyrifos Metabolite 3,5,6-trichloro-2-pyridinol to Eisenia Fetida in Different Soils

The present study utilized a biomarker response method to evaluate the effect of 3,5,6-trichloro-2-pyridinol (TCP) in artificial and natural soils on Eisenia fetida after 7, 14, 28, 42 and 56 days exposure. Results indicated that TCP induced excessive reactive oxygen species, caused oxidative stress and DNA damage to Eisenia fetida. Biomarker responses were standardized to calculate the Integrated Biomarker Response (IBR) index. The IBR index of three enzymes activities showed that TCP induced the enzymes activities of earthworm in red clay was stronger than the other three soils. Specifically, chlorpyrifos exposure group showed a lower toxicity than TCP exposure group after 28 days exposure but a higher toxicity than TCP exposure group after 56 days exposure. Despite the deficiencies of this study, the above information is of great significance for assessing the risk of chlorpyrifos and its metabolite TCP pollution in soil ecosystems.

Evaluation of biochemical treatments applied in polluted soils irrigated with low quality water for long periods of time through the CO2 efflux

<p class="042abstractstekst"><span lang="EN-US">To sightsee the bearings of the certain remediation amendments, usually applied in the bioremediation of soils irrigated with low quality water for extended periods on the indigenous microbial population, a greenhouse experiment was conducted at National Research Centre (NRC) where the soil ecosystem was supplied with varied mineral remediation amendments and the carbon dioxide (CO₂) refluxes were followed up. In this study, microbial activity through CO₂ efflux was taken as an indicator to evaluate the effectiveness of eight soil amendments in minimizing the hazards of inorganic pollutants in soil ecosystem irrigated with low quality water s for more than 40 years. Results showed that Ni and Zn were the most dominant contaminants that adversely influenced indigenous microbial activities in untreated soil, while Cu was the most persuasive. All trailed remediation amendments significantly minimized the hazards of inorganic pollutants in treated soil ecosystems. In addition, modified bentonite (Probentonite) was the best persuasive one. Mechanisms take place between trailed remediation amendments and inorganic pollutants in the studied soil ecosystems were discussed. In conclusion application of certain raw or modified clay minerals especially Probentonite could be a good tool in decreasing the rate of the studied inorganic pollutants in a contaminated soil ecosystem irrigated with low quality water for extended periods. </span></p>

Exploring the Occurrence Characteristics of Microplastics in Typical Maize Farmland Soils With Long-Term Plastic Film Mulching in Northern China

Microplastics pollution has been threatening the global environmental security, in which agricultural activities are considered as a main source of microplastics occurrence in soils. However, little is known about the occurrence characteristics of microplastics in agricultural soils with long-term plastic film mulching. Therefore, the abundance, distribution, and composition of microplastics were investigated by analyzing 225 soil samples collected from typical maize (Zea mays L.) planting zones with and without long-term (&gt;20 years) plastic film mulching in northern China. Microplastics abundance in mulched soils (754 ± 477 items kg–1) was significantly higher than that in non-mulched soils (376 ± 149 items kg–1), which indicated that plastic film mulching contributed half of microplastics in soils. Moreover, microplastics abundance was significantly positively related to the length of time with film mulching applied. The percentage of microplastics &lt;0.5 mm in mulched soils (50.9%) was significantly lower than that in non-mulched soils (62.2%). Microplastics abundance and size in mulched and non-mulched soils decreased with increased soil depth. Most microplastics were fragments of polypropylene, films of polyethylene, and fibers of polyester. The proportion of films in mulched soils was significantly higher than in non-mulched soils, whereas that of fibers was significantly higher in non-mulched soils. This study confirmed that long-term plastic film mulching increases microplastics pollution in agricultural soils, warranting further evaluation of the associated ecological risks of microplastics in soil ecosystems.

Determination of the Effects of Copper (Cu) and Lead (Pb) Heavy Metals on Soil Carbon and Nitrogen Mineralization

Heavy metal (HM) pollution has become one of the most important environmental problems of the present day, as a result of the developing industrial activities. Accordingly, it is important to understand microorganism activities in soil ecosystems that have been exposed to HMs for a long time. The aim of this study was to show the potential effects of ores on soil carbon and nitrogen mineralizations which were taken from copper (Cu) and lead (Pb) mines in Balıkesir-Balya and Kastamonu-Küre districts in Turkey. The carbon (C) and nitrogen (N) mineralizations were determined by using the CO2 respiration method (30 days) and the Parnas Wagner method (42 days) under the controlled laboratory conditions (28 °C, 80% of field capacity), respectively. It was observed that carbon mineralization decreased depending on the dose increase. 250 mg kg-1 treatment with Pb was lower than the control and there was a significant difference between them (P < 0.001). In terms of nitrogen mineralization rate (%), there was no significant difference among all treatments. According to the results, Pb affected microorganisms more negatively; however, the presence of Cu slightly decreased its negative effect. It is possible to conclude that carbon mineralization can be indicator for HM pollution in the soil. However, nitrogen mineralization was not a determining factor at HM pollution in this study.

Evolutionarily Conserved Core Rhizosphere Microbiota Promotes Host Performance and Fitness in Heavy Metal Accumulating Plants

Background: Persistent microbial symbioses offer the potential to confer greater fitness to the host under unfavorable conditions, but manipulation of such beneficial interactions requires a mechanistic understanding of the consistently important microbiome members for the plant. Here, use five phylogenetically divergent heavy metal (HM) accumulating plants as a model, we examined the composition, assembly and relationships of the core and active rhizosphere microbiota across diverse soils with varying concentrations of HMs and further explored their roles in host performance.Results: Our results showed that the rhizosphere bacterial communities were primarily determined by soil type, with plant species having a stronger influence on the microbial diversity and composition than rhizocompartment and soil pollution level. We found that different HM accumulating plants harbored a unique set of core taxa in the rhizosphere with Sphingomonas and Burkholderiaceae shared among them. Use of RNA-SIP further revealed that the core rhizosphere taxa phylogenetically overlapped with the active rhizobacteria feeding on carbon-rich rhizodeposits, suggesting that the specific root exudate components driving the core microbiomes may be common across different plant species. Several keystone taxa were part of the core microbiota and facilitated plant metal tolerance and accumulation when inoculated with SynCom comprising the core cohorts.Conclusions: Our results suggest that a conserved core root microbiota has evolved with HM accumulating plants via root metabolic cues and exhibited potential to increase plant fitness and phytoextraction of HM. This study has important implications for harnessing the persistent microbiome members to improve host performance and accelerate the plant-assisted restoration of contaminated soil ecosystems.

Soil plastispheres as hotpots of antibiotic resistance genes and potential pathogens

In the Anthropocene, increasing pervasive plastic pollution is creating a new environmental compartment, the plastisphere. How the plastisphere affects microbial communities and antibiotic resistance genes (ARGs) is an issue of global concern. Although this has been studied in aquatic ecosystems, our understanding of plastisphere microbiota in soil ecosystems remains poor. Here, we investigated plastisphere microbiota and ARGs of four types of microplastics (MPs) from diverse soil environments, and revealed effects of manure, temperature, and moisture on them. Our results showed that the MPs select for microbial communities in the plastisphere, and that these plastisphere communities are involved in diverse metabolic pathways, indicating that they could drive diverse ecological processes in the soil ecosystem. The relationship within plastisphere bacterial zero-radius operational taxonomic units (zOTUs) was predominantly positive, and neutral processes appeared to dominate community assembly. However, deterministic processes were more important in explaining the variance in ARGs in plastispheres. A range of potential pathogens and ARGs were detected in the plastisphere, which were enriched compared to the soil but varied across MPs and soil types. We further found that the addition of manure and elevation of soil temperature and moisture all enhance ARGs in plastispheres, and potential pathogens increase with soil moisture. These results suggested that plastispheres are habitats in which an increased potential pathogen abundance is spatially co-located with an increased abundance of ARGs under global change. Our findings provided new insights into the community ecology of the microbiome and antibiotic resistome of the soil plastisphere.

Root cap at soil interface: a driving force towards plant adaptation and development

Land plants harbour robust roots to grow in diverse soil ecosystems. The distal end of the primary root tip has specialized tissue, called “root cap.” The evolution of root cap-like structures in early plants rudimentary roots and well-developed root caps in vascular plants hints towards developing an adaptive trait for a localized plant habitat. Root cap interacts with soil and assists roots in penetrating the below ground, avoid/adsorb metals, uptake water, minerals, and regulates rhizosphere microbiota that drives plant-soil feedback. Besides, the root cap governs lateral root patterning and directs root growth in varying conditions. This review article presents the retrospective and our perspective on root cap characters for root-soil interaction. We discussed the anatomy of root cap among the different taxa of land plants and their relevance in diverse habitats and elucidated the root cap functions under various growth conditions. We took advantage of recently published single-cell RNAseq data and shed light on biological relevance of root cap cell-type enriched genes from arabidopsis, rice, maize, and tomato. Additionally, analyzed the transcription factor binding site enrichment in root cap enriched genes and constructed gene-regulatory networks operating in root cap to contribute its multi-faceted role in plant growth and adaptation.

Prevalence of Multi-Drug-Resistant bacterial strains in agricultural soils of Haryana, India

Due to continuous misuse or overuse of antibiotics for various purposes in farm animals, the present century has witnessed a rapid increase in the prevalence of multi-drug-resistant bacterial strains specifically in the soil ecosystems throughout the world. In view of this significant fact, the present study was designed to assess the prevalence and spread of antibiotic-resistant-bacteria in agricultural soils of Haryana State in India. For this, a total of 135 bacteria were isolated from the soils of organic and conventional farms spread throughout the State. All the isolates were tested for antibiotic resistance. It was observed that 53.33%, 2.96%, 17.77% and 16.29% of the total isolates were resistant to penicillin, tetracycline, streptomycin and erythromycin respectively. A total of 13 isolates exhibiting resistance to either four or any three antibiotics up to a concentration of 25µg/ml were considered as multi-drug-resistant. Further, 16S rRNA sequences were obtained. The distance matrix and the phylogenetic tree of the selected thirteen sequences was constructed. From the results, it was observed that multi-drug-resistant strains were obtained predominantly from the agricultural soils taken from organic farms while majority of isolates from conventional agricultural farm soils represented resistance against either a single, or up to two antibiotics.