Natural Soil Research Articles

The Application of Green Seismic Survey Technology in Forested Areas and Its Ecological and Economic Effectiveness: Methodology and Practice of Application

The issues surrounding the employment of technology targeted at enhancing environmental safety to increase the productivity of the reproduction process of the natural gas and oil resource base are equally important. The paper discusses the use of green seismic survey technology to determine the oil and gas potential of the subsoil. A methodological toolkit is proposed for carrying out technical and economic calculations to determine indicators of the environmental and economic efficiency of using innovative resource-saving technology for geological surveys in areas densely planted with forests. The purpose of the work is to establish the viability of employing resource-saving technology known as green seismic technology to search for promising hydrocarbon resources in forested areas and determine the expected environmental and economic benefits of geological exploration using the suggested enhanced methodology for their evaluation. The tasks set to achieve the goal were solved using methods of geological and economic assessment of the hydrocarbon raw material potential of territories and water areas; environmental assessments of the negative influence of anthropogenic environmental impacts on the natural environment; and economic and statistical methods of performing technical and economic calculations to determine performance indicators for the implementation of innovative projects in the field of geological exploration. The novelty of the results obtained lies in the proposed improved algorithm for conducting an environmental and economic assessment of geological exploration for hydrocarbon raw materials; a conceptual description of the green seismic technology; systematization of technical, economic, and environmental risks; and justification of new regional directions for geological exploration using resource-saving seismic exploration technology.

PFOA and PFOS induces mineralization of soil organic carbon by accelerating the consumption of dissolved organic carbon

The wide spread of Perfluoroalkyl substances (e.g., PFOA and PFOS) in soil can alter native soil geochemical properties and microbial communities through various approaches. Nonetheless, it is unclear that how PFOA and PFOS in soil affect the mineralization of soil organic carbon (SOC). A laboratory-scale culture experiment (180 d) was performed to explore the contribution of PFOA and PFOS to SOC dynamics and soil geochemical processes. Results showed that positive priming effect (PE) occurred in the short term (i.e., 30 days after PFOA and PFOS addition) and subsequently shifted to a slightly negative PE (i.e., 90 days) and remained in a significant negative PE thereafter (i.e., > 180 days). The PEs caused by PFOA and PFOS both accelerated the consumption of dissolved organic carbon (DOC), resulting in a significant increase in SOC mineralization (10.45%–127.36%) under the short-term incubation (30 d). As for long-term exposure (> 90 d), the organic carbon mineralization rate was significantly reduced (58.30%–65.24%) due to the excessive DOC consumption in the initial stage. High throughput analysis indicated that both PFOA and PFOS changed soil bacterial and fungal community structures, altered the relevant metabolic pathways and resulted in the enrichment of specific taxa.Graphical

Contributions of selenium-oxidizing bacteria to selenium biofortification and cadmium bioremediation in a native seleniferous Cd-polluted sandy loam soil

Selenium (Se) is a trace element that is essential for human health. Daily dietary Se intake is governed by the food chain through soil-plant systems. However, the cadmium (Cd) content tends to be excessive in seleniferous soil, in which Se and Cd have complex interactions. Therefore, it is a great challenge to grow crops containing appreciable amounts of Se but low amounts of Cd. We compared the effects of five Se-transforming bacteria on Se and Cd uptake by Brassica rapa L. in a native seleniferous Cd-polluted soil. The results showed that three Se-oxidizing bacteria (LX-1, LX-100, and T3F4) increased the Se content of the aboveground part of the plant by 330.8%, 309.5%, and 724.3%, respectively, compared to the control (p < 0.05). The three bacteria also reduced the aboveground Cd content by 15.1%, 40.4%, and 16.4%, respectively (p < 0.05). In contrast, the Se(IV)-reducing bacterium ES2–45 and weakly Se-transforming bacterium LX-4 had no effect on plant Se uptake, although they did decrease the aboveground Cd content. In addition, the three Se-oxidizing bacteria increased the Se available in the soil by 38.4%, 20.4%, and 24.0%, respectively, compared to the control (p < 0.05). The study results confirm the feasibility of using Se-oxidizing bacteria to simultaneously enhance plant Se content and reduce plant Cd content in seleniferous Cd-polluted soil.

Inverse vulcanization induced oxygen modified porous polysulfides for efficient sorption of heavy metals.

The applications of polysulfides derived from natural plant oil and sulfur via the inverse vulcanization in the removal of heavy metals from aqueous solutions suffered from their low porosity and scarce surface functionality because of their hydrophobic surfaces and bulk characteristics. In this study, polysulfides from sulfur and palm oil (PSPs) with significantly enhanced porosity (13.7-24.1 m2/g) and surface oxygen-containing functional groups (6.9-8.6 wt.%) were synthesized with the optimization of process conditions including reaction time, temperature, and mass ratios of sulfur/palm oil/NaCl/sodium citrate. PSPs were applied as sorbents to remove heavy metals present in aqueous solutions. The integration of porosity and oxygen modification allowed a fast kinetic (4.0h) and enhanced maximum sorption capacities for Pb(II) (218.5mg/g), Cu(II) (74.8mg/g), and Cr(III) (68.4mg/g) at pH 5.0 and T 298K comparing with polysulfides made without NaCl/sodium citrate. The sorption behaviors of Pb(II), Cu(II), and Cr(III) on PSPs were highly dependent on the solution pH values and ionic strength. The sorption presented excellent anti-interference capability for the coexisting cations and anions. The sorption processes were endothermic and spontaneous. This work would guide the preparation of porous polysulfides with surface modification as efficient sorbents to remediate heavy metals from aqueous solutions.

Experimental warming accelerates positive soil priming in a temperate grassland ecosystem

Unravelling biosphere feedback mechanisms is crucial for predicting the impacts of global warming. Soil priming, an effect of fresh plant-derived carbon (C) on native soil organic carbon (SOC) decomposition, is a key feedback mechanism that could release large amounts of soil C into the atmosphere. However, the impacts of climate warming on soil priming remain elusive. Here, we show that experimental warming accelerates soil priming by 12.7% in a temperate grassland. Warming alters bacterial communities, with 38% of unique active phylotypes detected under warming. The functional genes essential for soil C decomposition are also stimulated, which could be linked to priming effects. We incorporate lab-derived information into an ecosystem model showing that model parameter uncertainty can be reduced by 32–37%. Model simulations from 2010 to 2016 indicate an increase in soil C decomposition under warming, with a 9.1% rise in priming-induced CO2 emissions. If our findings can be generalized to other ecosystems over an extended period of time, soil priming could play an important role in terrestrial C cycle feedbacks and climate change.

Spent coffee grounds as a suitable alternative to standard soil in ecotoxicological tests.

Eisenia andrei is considered in OECD and ISO guidelines to be a suitable replacement for Eisenia fetida in ecotoxicological assays. This suggests that other alternative materials and methods could also be used in standard procedures for toxicity testing. The guidelines also favor using less time-consuming procedures and reducing costs and other limitations to ecotoxicological assessments. In recent years, spent coffee grounds (SCG) have been used to produce vermicompost and biochar and as an additive to organic fertilizers. In addition, the physicochemical characteristics of SCG indicate that the material is a suitable substrate for earthworms, with the organisms performing as well as in natural soil. In the present study, a battery of ecotoxicological tests was established with unwashed and washed SCG and a natural reference soil (LUFA 2.2). The test substrates were spiked with different concentrations of silver nitrate. Survival and reproduction of the earthworm E. andrei were assessed under different conditions, along with substrate basal respiration (SBR) as a proxy for microbial activity. Seedling emergence and the germination index of Lepidium sativum were also determined, following standard guidelines. Exposure to silver nitrate had similar effects on earthworm survival and reproduction, as the estimated effective concentrations (EC10 and EC50) in unwashed SCG and LUFA 2.2 overlapped. A hormetic effect was observed for SBR in LUFA 2.2 spiked with 12.8mg/kg but not in unwashed SCG. Both SBR and root development were inhibited by similar concentrations of silver nitrate in washed SCG. The findings indicate that unwashed SCG could potentially be used as a substrate in E. andrei toxicity tests and support the eventual inclusion of this material in the standard guidelines.

Intra and interspecific differences in desiccation tolerance in native and alien Antarctic springtails in geothermal grounds.

The extreme low humidity and temperatures in Antarctica make it one of the harsher areas for life on our planet. In a global change context, environmental barriers that prevented the arrival of alien species in Antarctica are weakening. Deception Island, one of the four active volcanoes of Antarctica, is especially vulnerable to the impacts of alien species. Geothermal areas (GA) in this Island offer unique microclimatic conditions that could differentially affect native and alien soil arthropods. Here we explore the desiccation tolerance of a native (Cryptopygus antarcticus) and an alien (Proisotoma minuta) springtail (Collembola) species to these extreme environmental conditions. GA and non-geothermal areas (NGA) were selected to evaluate intra- and interspecific variation in desiccation tolerance. Populations of P. minuta from GA had greater desiccation tolerance than populations from NGA. However, desiccation tolerance of C. antarcticus did not differ between GA and NGA. This native species had greater desiccation tolerance than the alien P. minuta, but also greater body size. Our findings show that the alien P. minuta responds differently to environmental conditions than the native C. antarcticus. Furthermore, body size may influence desiccation tolerance in these two springtail species.

Automated FerryBox monitoring reveals the first recorded river induced crude oil seep transport to the Strait of Magellan in southern Patagonia

This study presents the first documented occurrence of a natural crude oil seep plume associated with river discharge along the Strait of Magellan in southern Patagonia in modern times. Between September and December 2022, hydrocarbon signals were detected using a crude oil sensor integrated into a FerryBox system that traversed the Strait of Magellan and several channels of southern Patagonia, covering approximately 510 km. The highest levels of crude oil signals were observed in the mid-basin of the Strait of Magellan. These signals exhibited a strong negative correlation with sea surface salinity, coinciding with the water discharge from the San Juan River. Notably, during periods of high river discharge, typically exceeding 15 m3 s−1, a distinct crude oil plume was detected moving towards the Magellan Strait. Conversely, when river discharge fell below this threshold, no noticeable crude oil signal was observed. As river discharge decreased and winds intensified during the austral summer, the crude oil signal gradually dissipated. This observation suggests that the dispersion of crude oil becomes limited during periods of low river discharge, as buoyant currents remain confined close to the coast. Historical records indicate that this seep has been releasing hydrocarbons into the Strait of Magellan for at least the past 120 years, implying a long history of chronic crude oil input into this relatively isolated region of the world. This finding shows the potential contribution to the understanding of marine ecosystems dynamics and potential pollutants in poorly studied regions through the use of automated monitoring FerryBox system, enabling both spatial and temporal high-resolution surveys.

Evaluation of asphalt mixes performance characteristic with mustard oil as a rejuvenator

This study investigated the effects of adding natural renewable mustard oil (Mo) as a rejuvenator, and reclaimed asphalt pavement (RAP) to asphalt mixes for pavement maintenance and rehabilitation. Mo was utilized 10% by weight of binder with 30% RAP in modified asphalt mixes using two types of aggregate gradations. Performance characteristics of neat and modified asphalt mixes are evaluated through fatigue resistance, rutting resistance, and moisture damage resistance testing. The experimental results revealed that the addition of 10% Mo effectively rejuvenates asphalt mixes containing RAP by softening the aged binder typically from 6% to 14%. The bending fatigue resistance of modified asphalt mixes improves from 14% to 26%, rutting resistance decreases from 12% to 14% whereas moisture damage resistance also decreases from 12% to 16% respectively as compared to neat mixes. This research presents sustainable and cost-effective solution for utilizing Mo and RAP used in asphalt mixes for pavement maintenance and rehabilitation.

Land Use Change from Natural Tropical Forests to Managed Ecosystems Reduces Gross Nitrogen Production Rates and Increases the Soil Microbial Nitrogen Limitation.

Understanding the underlying mechanisms of soil microbial nitrogen (N) utilization under land use change is critical to evaluating soil N availability or limitation and its environmental consequences. A combination of soil gross N production and ecoenzymatic stoichiometry provides a promising avenue for nutrient limitation assessment in soil microbial metabolism. Gross N production via 15N tracing and ecoenzymatic stoichiometry through the vector and threshold element ratio (Vector-TER) model were quantified to evaluate the soil microbial N limitation in response to land use changes. We used tropical soil samples from a natural forest ecosystem and three managed ecosystems (paddy, rubber, and eucalyptus sites). Soil extracellular enzyme activities were significantly lower in managed ecosystems than in a natural forest. The Vector-TER model results indicated microbial carbon (C) and N limitations in the natural forest soil, and land use change from the natural forest to managed ecosystems increased the soil microbial N limitation. The soil microbial N limitation was positively related to gross N mineralization (GNM) and nitrification (GN) rates. The decrease in microbial biomass C and N as well as hydrolyzable ammonium N in managed ecosystems led to the decrease in N-acquiring enzymes, inhibiting GNM and GN rates and ultimately increasing the microbial N limitation. Soil GNM was also positively correlated with leucine aminopeptidase and β-N-acetylglucosaminidase. The results highlight that converting tropical natural forests to managed ecosystems can increase the soil microbial N limitation through reducing the soil microbial biomass and gross N production.

Influence of Date Palm-Based Biochar and Compost on Water Retention Properties of Soils with Different Sand Contents

Generally, soils of arid and semi-arid regions have low water retention properties due to high sand and low organic carbon contents. This study aimed at quantifying the effect of date palm-based organic amendments (OAs) on the water retention properties of two soils (sandy loam and silty loam), as well as the influence of sand supplementation (0.5–2 mm) on the magnitude of the effect of OAs. Different grain size distributions were obtained by adding sand to natural soils. For this purpose, sand was added to the two soils (1/3 and 2/3) and different soil-OA combinations were tested at a dose of 3% by mass: compost alone, biochar alone and a mixture of biochar and compost (50:50 in mass), in addition to unamended control soils. Soil water contents were measured at nine matric potentials ranging from the saturation to the permanent wilting point. Biochar was more efficient than compost at improving soil water retention. The effect of organic amendments on water retention increased with sand content. In most cases, soil water content values were significantly higher for biochar-amended soils than for unamended or compost-amended soils. The weakness of the effect of compost addition (if alone) was probably due to its properties and notably its high mineral content and electrical conductivity. Soil sand supplementation led to higher differences between the OA-amended soils and unamended soils. Changes in available water capacity reached +26% and +80% in a sandy loamy soil enriched with 2/3 sand and amended with compost and with biochar, respectively, compared to the unamended soil. These results show that sand content (and more generally, soil texture) influences the effect of OA application. Thus, the application of biochar from date palm residues in soil seems to be an effective solution to improve the water retention properties of coarse textured soils and contribute to optimizing the use of water resources in irrigated areas.

Experimental Investigation of the Mechanical Properties of Polypropylene Fiber-Reinforced Clay Soil and Development of Predictive Models: Effects of Fiber Length and Fiber Content

AbstractThis study investigated the mechanical properties of a low-plasticity clay soil reinforced with polypropylene (PP) fiber in various contents (0.05%, 0.10%, 0.15%, and 0.20%) and lengths (6, 12, and 19 mm). The reinforced specimens were subjected to unconsolidated-undrained (UU) triaxial compression tests under three different confining pressures (50, 100, and 200 kPa). The optimum fiber contents in specimens reinforced with 6-, 12-, and 19-mm PP fiber were determined as 0.15%, 0.15%, and 0.20%, respectively. As a result, the highest values regarding deviator stress at failure (σdev), energy absorption capacity (EAC), and shear strength parameters occurred in specimens containing 0.20% PP (19 mm). As a result of the reinforcement process, the most remarkable improvements in the σdev, cohesion, internal friction angle, and EAC values of the natural soil are 59.95%, 21.80%, 63%, and 34.70%, respectively. Linear and nonlinear relationships between σdev and fiber length, fiber content, and confining pressure were investigated by multiple linear regression and artificial neural network methods. Equations were generated to predict σdev of a low-plasticity clay soil reinforced with PP fiber and were made available to geotechnical researchers.

Assessing the extent of land degradation in the eThekwini municipality using land cover change and soil organic carbon

ABSTRACT More than 75% of the global land has already suffered degradation, leading to the recognition of land degradation as one of the foremost challenges society faces. This recognition stems from its profound adverse impacts on natural ecosystem functioning, biodiversity, soil productivity, and food availability. Consequently, understanding the spatial distribution of land degradation across all scales becomes imperative. This study employed land cover change and soil organic carbon (SOC) stock assessments to analyse land degradation within the eThekwini Municipality beyond the baseline period (2000–2015). Utilizing remote sensing and machine learning techniques, this research examined land degradation within the eThekwini Municipality over the period spanning 2000 to 2022. Landsat 7 (Enhanced Thematic Mapper Plus – ETM+), Landsat 8 (Operational Land Imager 1 - OLI1), and Landsat 9 (Operational Land Imager 2 - OLI2) images were employed to extract variables for both land cover change and SOC stock prediction through XGBoost, LightGBM, Random Forest (RF), and Support Vector Machine (SVM) models. Among these models, LightGBM demonstrates superior performance, achieving an overall accuracy of 80.646 in land cover predictions and 77.869 in SOC stock predictions. Analysis of land cover change within the eThekwini Municipality unveiled a shift from forests and shrubland landscapes to cropland and built-up areas. This shift results in the municipality encountering losses in SOC stock between 2015 and 2022. The model predicted that most SOC stock losses occur at the 20–50 cm depth (9.27%), in comparison to the 7.21% loss at the 0–20 cm depth. These findings underscore the pivotal role of remote sensing and machine learning in aiding policymakers to assess land degradation and implement pertinent measures to enhance the landscape.

Laboratory Evaluation of the Hydraulic Conductivity as a Function of Changes in the Particle Size of a Cubitermes Sp Termite Mound Soil Treated with Lime

This work characterizes the geotechnical properties and microstructure that served as a fundamental and more practical basis for describing the hydraulic conductivity of the lime-treated cubitermes sp termite mound soil. The results show that changes in particle size lead to a decrease in dry density and linear swelling. Permeability is strongly correlated with particle size distribution and compaction. Permeability increases up to the lime fixation point obtained at 6% of the lime content. Compaction for micropore reduction in treated soil is higher than in raw soil. The treated soil has a denser internal structure with agglomerations of dispersed clay particles. The increase in compaction energy reduces macropores and permeability, and the soil microstructure becomes homogeneous. Natural soil is highly impermeable, and soil-lime mixes are among the least draining materials. Higher values of hydraulic conductivity were obtained as a function of time. Soil and mixtures can be used in civil engineering works (earthworks). Correlations between hydraulic conductivity and particle size fractions are polylinear fits with R2 (0.962-0.993) and the Slogistic1 model with χ²(2.06E-15) for the mean silt fraction. This study is decisive for predicting hydraulic conductivity from the geotechnical properties of the soil, by solving the mathematical expressions of the models used.

Physico-Chemical Investigation and Antimicrobial Efficacy of Ozonated Oils: The Case Study of Commercial Ozonated Olive and Sunflower Seed Refined Oils.

Drug resistance represents one of the great plagues of our time worldwide. This largely limits the treatment of common infections and requires the development of new antibiotics or other alternative approaches. Noteworthy, the indiscriminate use of antibiotics is mostly responsible for the selection of mutations that confer drug resistance to microbes. In this regard, recently, ozone has been raising interest for its unique biological properties when dissolved in natural oils. Ozonated oils have been reported to act in a non-specific way on microorganisms hindering the acquisition of advantageous mutations that result in resistance. Here, we focused on the antimicrobial effect of two commercial olive (OOO) and sunflower seeds (OSO) oils. Nuclear magnetic resonance spectroscopy and thermal analysis showed the change in the chemical composition of the oils after ozonation treatment. Different ozonated oil concentrations were then used to evaluate their antimicrobial profile against Candida albicans, Enterococcus faecalis, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Escherichia coli by agar diffusion and broth dilution methods. Cytotoxicity was also evaluated in keratinocytes and epithelial cells. Overall, our results revealed that both OOO and OSO showed a potent microbicidal effect, especially against C. albicans (IC50 = OOO: 0.3 mg/mL and OSO: 0.2 mg/mL) and E. faecalis (IC50 = OOO: 0.4 mg/mL and OSO: 2.8 mg/mL) albeit exerting a certain effect also against S. aureus and E. coli. Moreover, both OOO and OSO do not yield any relevant cytotoxic effect at the active concentrations in both cell lines. This indicates that the ozonated oils studied are not toxic for mammalian cells despite exerting a potent antimicrobial effect on specific microorganisms. Therefore, OOO and OSO may be considered to integrate standard therapies in the treatment of common infections, likely overcoming drug resistance issues.

The ratio of denitrification end-products were influenced by soil pH and clay content across different texture classes in Oklahoma soils

Nitrous oxide (N2O) is a potent greenhouse gas that contributes to stratospheric ozone depletion and global climate change. Soil denitrification has two potential end-products, N2O and dinitrogen (N2), and the ratio of these end-products (N2O:(N2O+N2) or the N2O ratio) is controlled by various factors. This study aims to quantify the influence of soil pH on the ratio of denitrification end-products in Oklahoma soils with different soil textures. Six natural grassland soils encompassing three distinct soil textures were incubated in the laboratory under natural and modified pH with an overall tested pH ranging from 2 to 10. Denitrification end-products were measured in the laboratory using the acetylene inhibition technique and further estimated using a process-based biogeochemical model. Both the laboratory and model results showed that soil pH and texture influenced the ratio of the denitrification end-products. Generally, as soil pH increased the N2O ratio decreased, although both lab and model results indicated that this relationship was not linear. Soil texture may have an indirect effect on the N2O ratio, as two soils of the same texture could have different N2O ratios. However, clay percentage of the soil did show a linear positive correlation with the N2O ratio, suggesting components of soil texture may be more influential than others. Overall, soil pH was a controlling factor in the ratio of denitrification end-products and the newly observed nonlinear relationship warrants further study, particularly when considering its effects in different soil textures.

Effect of natural attractant essential oil from Ocimum gratisimum from Timor Island against fruit flies

Ocimum gratisimum, well-adapted to arid regions in East Nusa Tenggara, has essential oil that attracts fruit flies, pest important affecting crops like mango and jackfruit. This study aims to assess the impact of O. gratisimum essential oil on the diversity of fruit flies on these plants. The essential oil, source from leaves of O. gratisimum, was obtained from the Bioscience Laboratory of the University Nusa Cendana, East Nusa Tenggara, Kupang, Indonesia. It was applied to mango and jackfruit plants in Baumata Village, Taebenu District, Kupang Regency, East Nusa Tenggara. For experiment, total of 0.2 µL of O. gratisimum essential oil was carefully placed on a cotton swab, which was subsequently positioned within traps constructed using 1.5-L mineral bottles. The results of this study indicated that the essential oil extracted from O. gratisimum leaves had the capacity to attract Bacrtocera umbrosa and Bactrocera dorsalis flies when applied on mango plants. In case of jackfruit plants, the traps successfully lured B. umbrosa, B. dorsalis, and Bactrocera musae. This attraction contains methyl eugenol in the oil derived from O. gratisimum.

First Report of Leaf Spot Blight of Camellia oleifera Caused by Diaporthe mahothocarpus in China.

Camellia oleifera Abel. is one of the native and important natural edible oil species in China. The cultivation of C. oleifera has vigorously increased in Guizhou Province in recent years. From June to August 2022, a severe leaf spot blight was observed on C. oleifera in Longli Plantation, with an incidence of 53.5% (n=200), which caused severe defoliation, negatively affected plant growth, and led to significant economic losses. Pale yellow and sub-circular leaf spots of 2-5 mm in diameter first appeared in the margin. The center of the spots then turned grey, and the edges turned brown. The symptomatic leaves gradually developed symptoms of blight with some brown acervular conidiomata, died, and fell off, with many deep black spots on the leaves (Fig. 1A-B). The fungal isolates GZU-Y2 and GZU-Y3 were obtained from the infected leaves of five-year-old symptomatic C. oleifera trees using the tissue isolation method, and a voucher specimen was deposited in the Forest Protection Laboratory, Guizhou University. Cultures grown on potato dextrose agar medium (PDA) were incubated at 28℃, 16L/8D. A round cream-like colony was formed on PDA, with a white surface, while the back gradually turned brown (Fig. 1C-E). The aerial hypha grew vigorously with an initial milky white color before turning grayish white. At 10 days after incubation, the pycnidia were dark brown to black and spherical, with a diameter of 563.3 μm (500 to 700) (n=20). The alpha conidia were unicellular, hyaline, aseptate, oval or fusiform and measured 6.1 μm (4.1 to 8.0) × 2.6 μm (1.9 to 3.6) (n=50). However, no beta conidia were observed (Fig. 1I). For further identification, total DNA from the pure culture was extracted using a DNA extraction kit (Sangon, Shanghai, China), and the internal transcribed spacer (ITS), translation elongation factor 1-α (TEF-1α), and beta-tubulin (TUB2) were amplified by PCR using the primers ITS1/ITS4 (White et al., 1990), EF1-728F/EF1-986R (Carbone and Kohn, 1999) and Bt2a/Bt2b (Glass and Donaldson, 1995), respectively, and sequenced for a BLASTn analysis and phylogenetic tree construction. The sequences of ITS, TEF-1α and TUB2 were deposited in GenBank as accession numbers OQ168242 (99.25%), OQ689451 (99.71%) and OQ689453 (100.00%) for GZU-Y2 and OQ674554 (99.25%), OQ689452 (99.71%) and OQ689454 (100.00%) for GZU-Y3, respectively. A phylogenetic tree (Fig. 2) was constructed with the software MEGA X using the Neighbor-Joining algorithm (Felsenstein, 1985). Based on its morphological and molecular characteristics, the pathogen was identified as Diaporthe mahothocarpus, one of the synonyms of D. eres and the teleomorph of Phomopsis mahothocarpi (Gao et al., 2014 and 2015; Chaisiri et al., 2021). A pathogenicity test was conducted by spraying spore suspensions (2 × 107 spores/mL) of isolate GZU-Y2 on the leaves of 20 pots of annual C. oleifera seedlings in vivo. The same number of control seedings were sprayed with sterile water. The seedlings were placed at a constant room temperature of 28°C, with the inoculation points wrapped in Parafilm for 5 d to retain moisture. After 10 d, typical symptoms appeared on the inoculated leaves (Fig. 1F-H), and the re-isolated fungal culture was identical in morphology and ITS sequence to that originally obtained, fulfilling Koch's postulates. To our knowledge, this is the first report of D. mahothocarpus causing leaf spot blight of C. oleifera in China. In our future work, we tend to study the green prevention and control of this disease.

Dibutyl phthalate degradation by Paenarthrobacter ureafaciens PB10 through downstream product myristic acid and its bioremediation potential in contaminated soil

Dibutyl phthalate (DBP) is a widely used plasticizer to make plastic flexible and long-lasting. It is easily accessible in a broad spectrum of environments as a result of the rising level of plastic pollution. This compound is considered a top-priority toxicant and persistent organic pollutant by international environmental agencies for its endocrine disruptive and carcinogenic propensities. To mitigate the DBP in the soil, one DBP-degrading bacterial strain was isolated from a plastic-polluted landfill and identified as Paenarthrobacter ureafaciens PB10 by 16S rRNA gene sequence-based homology. The strain was found to develop a distinct transparent halo zone around grown colonies on an agar plate supplemented with DBP. The addition of yeast extract (100 mg/L) as a nutrient source accelerated cell biomass production and DBP degradation rate; however, the presence of glucose suppressed DBP degradation by the PB10 strain without affecting its ability to proliferate. The strain PB10 was efficient in eliminating DBP under various pH conditions (5.0–8.0). Maximum cell growth and degradation of 99.49% at 300 mg/L DBP were achieved in 72 h at the optimized mineral salt medium (MS) conditions of pH 7.0 and 32 °C. Despite that, when the concentration of DBP rose to 3000 mg/L, the DBP depletion rate was measured at 79.34% in 72 h. Some novel intermediate metabolites, like myristic acid, hexadecanoic acid, stearic acid, and the methyl derivative of 4-hydroxyphenyl acetate, along with monobutyl phthalate and phthalic acid, were detected in the downstream degradation process of DBP through GC-MS profiling. Furthermore, in synchronization with native soil microbes, this PB10 strain successfully removed a notable amount of DBP (up to 54.11%) from contaminated soil under microcosm study after 10 d. Thus, PB10 has effective DBP removal ability and is considered a potential candidate for bioremediation in DBP-contaminated sites.

Chain Elongation Using Native Soil Inocula: Exceptional n-Caproate Biosynthesis Performance and Microbial Mechanisms

This study demonstrates the feasibility and effectiveness of utilizing native soils as a resource for inocula to produce n-caproate through the chain elongation (CE) platform, offering new insights into anaerobic soil processes. The results reveal that all five of the tested soil types exhibit CE activity when supplied with high concentrations of ethanol and acetate, highlighting the suitability of soil as an ideal source for n-caproate production. Compared with anaerobic sludge and pit mud, the native soil CE system exhibited higher selectivity (60.53%), specificity (82.32%), carbon distribution (60.00%), electron transfer efficiency (165.00%), and conductivity (0.59 ms∙cm−1). Kinetic analysis further confirmed the superiority of soil in terms of a shorter lag time and higher yield. A microbial community analysis indicated a positive correlation between the relative abundances of Pseudomonas, Azotobacter, and Clostridium and n-caproate production. Moreover, metagenomics analysis revealed a higher abundance of functional genes in key microbial species, providing direct insights into the pathways involved in n-caproate formation, including in situ CO2 utilization, ethanol oxidation, fatty acid biosynthesis (FAB), and reverse beta-oxidation (RBO). The numerous functions in FAB and RBO are primarily associated with Pseudomonas, Clostridium, Rhodococcus, Stenotrophomonas, and Geobacter, suggesting that these genera may play roles that are involved or associated with the CE process. Overall, this innovative inoculation strategy offers an efficient microbial source for n-caproate production, underscoring the importance of considering CE activity in anaerobic soil microbial ecology and holding potential for significant economic and environmental benefits through soil consortia exploration.