Glyphosate Degradation In Soil Research Articles

Subtle microbial community changes despite rapid glyphosate degradation in microcosms with four German agricultural soils

Glyphosate is the world's most widely applied herbicide. Despite its extensive and heavy use in agriculture and forestry, the microbial key players involved in glyphosate breakdown and the impact of this compound on the soil microbiota including fungi is not fully understood. Here, we used microcosm experiments to determine the impact of glyphosate application on the microbial community structure and abundance of four different agricultural soils from the Ammer valley, Germany, with a history of glyphosate application. We identified putative glyphosate degraders that could be active under in-situ conditions. Glyphosate was applied to the soils in a single dose of 15 mg·kg−1, which were incubated in the dark with 60 % water-filled pore space at 20 °C for 56 days. Soil samples were taken on the day of glyphosate addition (day 0) and after 7, 28 and 56 days. Capillary electrophoresis-mass spectrometry was used to quantify glyphosate and its major transformation product aminomethylphosphonic acid. Changes in the microbial community structure and abundance were evaluated using 16S rRNA gene or internal transcribed spacer region amplicon sequencing and qPCR. Our findings demonstrate that glyphosate was rapidly degraded in the four soils, with 60–85 % of the applied glyphosate disappearing within 7 days. However, the observed impact of glyphosate application on the microbial community composition was minimal and, notably, there was no significant time-dependent glyphosate effect at 7 days across all four soils. This suggests that glyphosate degradation in soil might be a concerted effort by a wide microbial network or it might be occurring co-metabolically. In addition, the sorption/desorption dynamics of glyphosate with the soil matrix can heavily influence its bioavailability, further reasoning the subtle effects observed on the microbial community structure.

Unlocking the potential of glyphosate-resistant bacterial strains in biodegradation and maize growth.

Glyphosate [N-(phosphonomethyl)-glycine] is a non-selective herbicide with a broad spectrum activity that is commonly used to control perennial vegetation in agricultural fields. The widespread utilization of glyphosate in agriculture leads to soil, water, and food crop contamination, resulting in human and environmental health consequences. Therefore, it is imperative to devise techniques for enhancing the degradation of glyphosate in soil. Rhizobacteria play a crucial role in degrading organic contaminants. Limited work has been done on exploring the capabilities of indigenously existing glyphosate-degrading rhizobacteria in Pakistani soils. This research attempts to discover whether native bacteria have the glyphosate-degrading ability for a sustainable solution to glyphosate contamination. Therefore, this study explored the potential of 11 native strains isolated from the soil with repeated glyphosate application history and showed resistance against glyphosate at higher concentrations (200 mg kg-1). Five out of eleven strains outperformed in glyphosate degradation and plant growth promotion. High-pressure liquid chromatography showed that, on average, these five strains degraded 98% glyphosate. In addition, these strains promote maize seed germination index and shoot and root fresh biomass up to 73 and 91%, respectively. Furthermore, inoculation gave an average increase of acid phosphatase (57.97%), alkaline phosphatase (1.76-fold), and dehydrogenase activity (1.75-fold) in glyphosate-contaminated soil. The findings indicated the importance of using indigenous rhizobacteria to degrade glyphosate. Therefore, by maintaining soil health, indigenous soil biodiversity can work effectively for the bioremediation of contaminated soils and sustainable crop production in a world facing food security.

Application of urea hydrogen peroxide: Degradation of glyphosate in soil and effect on ammonia nitrogen effectiveness and enzyme activity

Glyphosate is one of the most widely used pesticides globally. However, glyphosate and its residual metabolite, aminomethyl phosphonic acid (AMPA), are persistent and mobile chemicals. Large amounts of glyphosate residue can accumulate in the environment, causing adverse effects in organisms. Urea hydrogen peroxide (UHP) in soil slow-release H2O2 undergoes a Fenton-like reaction with Fe2+, and the resulting hydroxyl radical (·OH) degrades glyphosate. This experiment investigated the effects of three fertilisers (UHP, ferrous sulphate, and urea) on the degradation of glyphosate in agricultural soils and their effects on soil ammonia nitrogen effectiveness and enzyme activity. Among all treatments, the half-life of glyphosate in the mixed application of UHP and ferrous sulphate was the shortest (11.9 d), and its degradation rate was the highest (70.64%), degrading within 28 d. Throughout the experimental cycle, in 1–7 d, the application of UHP reduced the effect on indigenous microorganisms and maintained nitrogen availability and enzyme activity in the soil; in 7–14 d, the mixed application of UHP and ferrous sulphate alleviated the nitrification of soil nitrogen and reduced the loss of ammonia from the soil; in 14–28 d, the mixed or single application of UHP and ferrous sulphate and the low dose of glyphosate remaining in the soil had a catalytic effect on enzyme activity, promoting the secretion of catalase and nitratase, which participate in soil glyphosate degradation and nitrogen cycling. Therefore, this study provides a scientific basis for the in-situ remediation of herbicide-contaminated soil in agricultural fields using chemical fertilisers.

Characterization of a novel glyphosate-degrading bacterial species, Chryseobacterium sp. Y16C, and evaluation of its effects on microbial communities in glyphosate-contaminated soil

Widespread use of the herbicide glyphosate in agriculture has resulted in serious environmental problems. Thus, environment-friendly technological solutions are urgently needed for the removal of residual glyphosate from soil. Here, we successfully isolated a novel bacterial strain, Chryseobacterium sp. Y16C, which efficiently degrades glyphosate and its main metabolite aminomethylphosphonic acid (AMPA). Strain Y16C was found to completely degrade glyphosate at 400 mg·L-1 concentration within four days. Kinetics analysis indicated that glyphosate biodegradation was concentration-dependent, with a maximum specific degradation rate, half-saturation constant, and inhibition constant of 0.91459 d-1, 15.79796 mg·L-1, and 290.28133 mg·L-1, respectively. AMPA was identified as the major degradation product of glyphosate degradation, suggesting that glyphosate was first degraded via cleavage of its C–N bond prior to subsequent metabolic degradation. Strain Y16C was also found to tolerate and degrade AMPA at concentrations up to 800 mg·L-1. Moreover, strain Y16C accelerated glyphosate degradation in soil indirectly by inducing a slight alteration in the diversity and composition of soil microbial community. Taken together, our results suggest that strain Y16C may be a potential microbial agent for bioremediation of glyphosate-contaminated soil.

Glyphosate Biodegradation Potential in Soil Based on Glycine Oxidase Gene (thiO) from Bradyrhizobium.

Despite the intensive use of glyphosate(GP) and its ubiquitous presence in the environment, studies addressing the presence of microbial genes involved in glyphosate degradation in natural conditions are scarce. Based on the agronomical importance of Bradyrhizobium genus and its metabolic versatility, we tested the hypothesis that species or genotypes of Bradyrhizobium could be a proxy for GP degrader potential in soil. A quantitative PCR assay was designed to target a specific region of the glycine oxidase gene (thiO), involved in the oxidation of glyphosate to AMPA, from known sequences of Bradyrhizobium species. The abundance of the thiO gene was determined in response to herbicide application in soils with different GP exposure history both under field and microcosm conditions. The gene coding for RNA polymerase subunitB (rpoB) was usedas a reference for the abundance of total Bradyrhizobia. The assay using the designed primers was linear over a very large concentration range of the target and showed high efficiency and specificity. In a field experiment, there was a differential response related to the history of glyphosate use and the native Bradyrhizobium genotypes. In a soil without previous exposure to herbicides, thiO gene increased over time after glyphosate application with most genotypes belonging to the B. jicamae and B. elkanni supergroups. Conversely, in an agricultural soil with more than 10 years of continuous glyphosate application, the abundance of thiO gene decreased and most genotypes belonged to B. japonicum supergroup. In a microcosm assay, the amount of herbicide degraded after a single application was positively correlated to the number of thiO copies in different agricultural soils from the Pampean Region. Our results suggest that Bradyrhizobium species are differently involved in glyphosate degradation, denoting the existence of metabolically versatile microorganisms which can be explored for sustainable agriculture practices. The relationship between the abundance of thiO gene and the GP degraded in soil point to the use of thiO gene as a proxy for GP degradation in soil.

Role of soil bacterial consortia on glyphosate degradation and growth of maize seedlings

Pre-growing weed control by glyphosate herbicides is effective for increasing yield, but glyphosate residues in the soil might reduce soil quality and can accumulate in agricultural products. Naturally, microbes are able to breakdown glyphosate into nontoxic substances orthophosphate and glycine. Glyphosate degradation in soil by single soil microbes are reported elsewhere, but the information about glyphosate removal by soil bacterial consortia was limited. The objective of this research was to determine the effect of carbon (C), nitrogen (N), and phosphorus (P) composition in liquid media to increase glyphosate degradation and its degradation product by soil bacterial consortia and 2) verify the effect of bacterial consortia on maize seedlings growth, their N and P uptake, as well as total and soluble P in soil. Glyphosate degradation test was set up by incubating bacterial consortia in a different composition of C-N-P liquid basal media. Greenhouse experiment has been performed in a randomized block design to treat maize grown in Inceptisols with bacterial and glyphosate application. The results showed that C-N-P composition of liquid media affected the concentration of glyphosate, as well as orthophosphate and glycine as by-products. In-planta experiment verified that inoculation of glyphosate-degrading bacterial to maize seedling grown in glyphosate-contaminated soil enabled to enhance shoot dry weight of maize seedling and N and P uptake at 4 weeks after inoculation.

Glyphosate contaminated soil remediation by atmospheric pressure dielectric barrier discharge plasma and its residual toxicity evaluation

Glyphosate was one of the most widely used herbicides in the world. Remediation of glyphosate-contaminated soil was conducted using atmospheric pressure dielectric barrier discharge (DBD) plasma. The feasibility of glyphosate degradation in soil was explored, and the soil leachate toxicity after remediation was assessed via a seed germination test. The experimental results showed that approximately 93.9% of glyphosate was degraded within 45min of DBD plasma treatment with an energy yield of 0.47gkWh⿿1, and the degradation process fitted the first-order kinetic model. Increasing the discharge voltage and decreasing the organic matter content of the soil were both found to facilitate glyphosate degradation. There existed appropriate soil moisture to realize high glyphosate degradation efficiency. Glyphosate mineralization was confirmed by changes of total organic carbon (TOC), chemical oxygen demand (COD), PO43⿿ and NO3⿿. The degradation intermediates including glycine, aminomethylphosphonic acid, acetic acid, formic acid, PO43⿿ and NO3⿿, CO2 and CO were observed. A possible pathway for glyphosate degradation in the soil using this system was proposed. Based on the soil leachate toxicity test using wheat seed germination, the soil did not exhibit any hazardous effects following high-efficiency glyphosate degradation.

Glyphosate biodegradation and potential soil bioremediation by Bacillus subtilis strain Bs-15.

Glyphosate and glyphosate-containing herbicides have an adverse effect on mammals, humans, and soil microbial ecosystems. Therefore, it is important to develop methods for enhancing glyphosate degradation in soil through bioremediation. We investigated the potential of glyphosate degradation and bioremediation in soil by Bacillus subtilis Bs-15. Bs-15 grew well at high concentrations of glyphosate; the maximum concentration tolerated by Bs-15 reached 40,000 mg/L. The optimal conditions for bacterial growth and glyphosate degradation were less than 10,000 mg/L glyphosate, with a temperature of 35°C and a pH of 8.0. Optimal fermentation occurred at 180 rpm for 60 h with an inoculum ratio of 4%. Bs-15 degraded 17.65% (12 h) to 66.97% (96 h) of glyphosate in sterile soil and 19.01% (12 h) to 71.57% (96 h) in unsterilized soil. Using a BIOLOG ECO plate test, we observed no significant difference in average well color development values between the soil inoculated with Bs-15 and the control soil before 72 h, although there was a significant difference (P < 0.01) after 72 h. In the presence of Bs-15, the 5 functional diversity indices (Shannon index, Shannon uniformity, Simpson index, McIntosh index, and McIntosh uniformity) were greater (P < 0.01) compared with the control soil. These results indicate that Bs-15 could be used to alleviate contamination from glyphosate-containing herbicides, increasing the microbial functional diversity in glyphosate-contaminated soils and thus enhancing the bioremediation of glyphosate-contaminated soils.

The effects of biochar, wood vinegar and plants on glyphosate leaching and degradation

Although glyphosate is a commonly used herbicide, its impacts on ecosystems are not well understood. A pot experiment, was established to explore the potential impacts of biochar, wood vinegar, and plants on the environmental fate of glyphosate. In the presence of plants (Lolium perenne), and irrespective of the presence of biochar or wood vinegar, leaching of glyphosate through the soil was multiple compared to the plant free systems. However, the addition of biochar to the soil decreased the leaching of glyphosate irrespective of plants. Soils treated with biochar–wood vinegar mixture showed the lowest glyphosate leaching, both with and without plants. Biochar, wood vinegar or plants, alone, had no effect on the degradation of glyphosate in soil. When the plants were present the degradation of glyphosate was highest in soils treated with biochar–wood vinegar mixture. Our results imply that biochar in particular can be applied as a soil improving agent to reduce the potential environmental risks to aquatic environments caused by glyphosate

Degradation of glyphosate in soil photocatalyzed by Fe3O4/SiO2/TiO2 under solar light.

In this study, Fe3O4/SiO2/TiO2 photocatalyst was prepared via a sol-gel method, and Fe3O4 particles were used as the core of the colloid. Diffraction peaks of Fe3O4 crystals are not found by XRD characterization, indicating that Fe3O4 particles are well encapsulated by SiO2. FTIR characterization shows that diffraction peaks of Ti-O-Si chemical bonds become obvious when the Fe3O4 loading is more than 0.5%. SEM characterization indicates that agglomeration occurs in the Fe3O4/SiO2/TiO2 photocatalyst, whereas photocatalysts modified by Fe3O4/SiO2 present excellent visible light absorption performance and photocatalytic activity, especially when the Fe3O4 loading is 0.5%. Photocatalytic degradation of glyphosate in soil by these photocatalysts under solar irradiation was investigated. Results show that 0.5% Fe3O4/SiO2/TiO2 has the best photocatalytic activity. The best moisture content of soil is 30%∼50%. Degradation efficiency of glyphosate reaches 89% in 2 h when the dosage of photocatalyst is 0.4 g/100 g (soil), and it increased slowly when more photocatalyst was used. Soil thickness is a very important factor for the photocatalytic rate. The thinner the soil is, the better the glyphosate degradation is. Degradation of glyphosate is not obviously affected by sunlight intensity when the intensity is below 6 mW/cm2 or above 10 mW/cm2, but it is accelerated significantly when the sunlight intensity increases from 6 mW/cm2 to 10 mW/cm2.

Glyphosate utilization byPseudomonas sp. andAlcaligenes sp. isolated from environmental sources

A total of 21 bacterial cultures were isolated that could utilize glyphosate (N-phosphonomethyl glycine) as a sole source of phosphorus in a mineral salts medium. Sources of inocula for enrichment cultures included aerobic digester liquid, raw sewage, trickling filter effluent, pesticide disposal pit liquid, and soil. Eleven cultures were identified asPseudomonas sp., one asPseudomonas stutzeri, and nine asAlcaligenes sp. Aminomethylphosphonic acid, the major metabolic intermediate of glyphosate degradation in soil, could also serve as a sole phosphorus source for all 21 isolates. Neither glyphosate nor aminomethylphosphonic acid could serve as carbon sources in mineral salts media. Experiments withPseudomonas sp. SG-1 (isolated from aerobic digester liquid) suggested that enzymatic activity responsible for glyphosate degradation was intracellular, inducible, and required the cofactors pyruvate and pyridoxal phosphate. The degradation pathway for glyphosate in this culture may be similar to that previously reported for aminoethylphosphonic acid.

Metabolism and degradation of glyphosphate in soil and water.

Metabolism and degradation of glyphosphate in soil and water.