Recent advances in glyphosate biodegradation

Engineering multi-degrading bacterial communities to bioremediate soils contaminated with pesticides residues

Parallel to the important use of pesticides in conventional agriculture there is a growing interest for green technologies to clear contaminated soil from pesticides and their degradation products. Bioaugmentation i. e. the inoculation of degrading micro-organisms in polluted soil, is a promising method still in needs of further developments. Specifically, improvements in the understanding of how degrading microorganisms must overcome abiotic filters and interact with the autochthonous microbial communities are needed in order to efficiently design bioremediation strategies. Here we designed a protocol aiming at studying the degradation of two herbicides, glyphosate (GLY) and isoproturon (IPU), via experimental modifications of two source bacterial communities. We used statistical methods stemming from genomic prediction to link community composition to herbicides degradation potentials. Our approach proved to be efficient with correlation estimates over 0.8 - between model predictions and measured pesticide degradation values. Multi-degrading bacterial communities were obtained by coalescing bacterial communities with high GLY or IPU degradation ability based on their community-level properties. Finally, we evaluated the efficiency of constructed multi-degrading communities to remove pesticide contamination in a different soil. While results are less clear in the case of GLY, we showed an efficient transfer of degrading capacities towards the receiving soil even at relatively low inoculation levels in the case of IPU. Altogether, we developed an innovative protocol for building multi-degrading simplified bacterial communities with the help of genomic prediction tools and coalescence, and proved their efficiency in a contaminated soil.

Glyphosate as a Food Contaminant: Main Sources, Detection Levels, and Implications for Human and Public Health

Glyphosate is a broad-spectrum pesticide that has become the most widely used herbicide globally. However, concerns have risen regarding its potential health impacts due to food contamination. Studies have detected glyphosate in human blood and urine samples, indicating human exposure and its persistence in the organism. A growing body of literature has reported the health risks concerning glyphosate exposure, suggesting that the daily intake of contaminated food and water poses a public health concern. Furthermore, countries with high glyphosate usage and lenient regulations regarding food and water contamination may face more severe consequences. In this context, in this review, we examined the literature regarding food contamination by glyphosate, discussed its detection methods, and highlighted its risks to human health.

An integrated approach to assess human health risk of neonicotinoid insecticides in surface water of the Yangtze River Basin, China

Neonicotinoids are widely used insecticides that have raised considerable concerns for both environmental and human health. However, there lack of comprehensive evaluation of their accumulation in surface water ecosystems and exposure to various human groups. Additionally, there's a distinct lack of scientific evidence describing the carcinogenic and non-carcinogenic impacts of neonicotinoids from surface water. Using an integrated approach employing the Relative Potency Factor (RPF), Hazard Index (HI), and Monte Carlo Simulation (MCS), the study assessed neonicotinoid exposure and risk to four demographic groups via dermal contact and mistaken oral intake pathways in the Yangtze River Basin (YRB), China. Neonicotinoid concentrations range from 0.1 to 408.12 ng/L, indicating potential risk (10-3 to 10-1) across the studied demographic groups. The Incremental Lifetime Cancer Risk (ILCR) for dermal contact was within a moderate range of 2.00 × 10-3 to 1.67 × 10-2, while the mistaken oral intake was also within a moderate range of 3.07 × 10-3 to 7.05 × 10-3. The Hazard Index (HI) for dermal exposure ranged from 1.49 × 10-2 to 0.125, while for mistaken oral intake, it varied between 2.69 × 10-2 and 0.14. The findings highlight the importance of implementing specific interventions to address neonicotinoid exposure, especially among demographic groups that are more susceptible. This research underscores the urgent need for targeted strategies to address neonicotinoid risks to vulnerable populations within the YRB while contributing to insights for effective policies to mitigate neonicotinoid exposure in surface water ecosystems globally.

Glyphosate resistance and biodegradation by Burkholderia cenocepacia CEIB S5-2

Glyphosate is a broad spectrum and non-selective herbicide employed to control different weeds in agricultural and urban zones and to facilitate the harvest of various crops. Currently, glyphosate-based formulations are the most employed herbicides in agriculture worldwide. Extensive use of glyphosate has been related to environmental pollution events and adverse effects on non-target organisms, including humans. Reducing the presence of glyphosate in the environment and its potential adverse effects requires the development of remediation and treatment alternatives. Bioremediation with microorganisms has been proposed as a feasible alternative for treating glyphosate pollution. The present study reports the glyphosate resistance profile and degradation capacity of the bacterial strain Burkholderia cenocepacia CEIB S5-2, isolated from an agricultural field in Morelos-México. According to the agar plates and the liquid media inhibition assays, the bacterial strain can resist glyphosate exposure at high concentrations, 2000 mg·L-1. In the degradation assays, the bacterial strain was capable of fast degrading glyphosate (50 mg·L-1) and the primary degradation metabolite aminomethylphosphonic acid (AMPA) in just eight hours. The analysis of the genomic data of B. cenocepacia CEIB S5-2 revealed the presence of genes that encode enzymes implicated in glyphosate biodegradation through the two metabolic pathways reported, sarcosine and AMPA. This investigation provides novel information about the potential of species of the genus Burkholderia in the degradation of the herbicide glyphosate and its main degradation metabolite (AMPA). Furthermore, the analysis of genomic information allowed us to propose for the first time a metabolic route related to the degradation of glyphosate in this bacterial group. According to the findings of this study, B. cenocepacia CEIB S5-2 displays a great glyphosate biodegradation capability and has the potential to be implemented in glyphosate bioremediation approaches.

Toxicity of glyphosate to animals: A meta-analytical approach

Glyphosate (GLY)-based herbicides (GBHs) are the most commonly applied pesticide worldwide, and non-target organisms (e.g., animals) are now regularly exposed to GLY and GBHs due to the accumulation of these chemicals in many environments. Although GLY/GBH was previously considered to be non-toxic, growing evidence indicates that GLY/GBH negatively affects some animal taxa. However, there has been no systematic analysis quantifying its toxicity to animals. Therefore, we used a meta-analytical approach to determine whether there is a demonstrable effect of GLY/GBH toxicity across animals. We further addressed whether the effects of GLY/GBH vary due to (1) taxon (invertebrate vs. vertebrate), (2) habitat (aquatic vs. terrestrial), (3) type of biological response (behavior vs. physiology vs. survival), and (4) dosage or concentration of GLY/GBH. Using this approach, we also determined whether adjuvants (e.g., surfactants) in commercial formulations of GBHs increased toxicity for animals relative to exposure to GLY alone. We analyzed 1282 observations from 121 articles. We conclude that GLY is generally sub-lethally toxic for animals, particularly for animals in aquatic or marine habitats, and that toxicity did not exhibit dose-dependency. Yet, our analyses detected evidence for widespread publication bias so we encourage continued experimental investigations to better understand factors influencing GLY/GBH toxicity to animals.

Occurrence, distribution and ecological risk assessment of herbicide residues in cropland soils from the Mollisols region of Northeast China

The first systematic and comprehensive investigation of herbicide residues was conducted by identifying their spatial distribution, influencing factors and ecological risk in cropland soils from the Mollisols region covering 109 million hm2 in Northeast China. Fifty-six herbicides were detected with total herbicide concentrations ranging from 1.01 to 1558.13 μg/kg (mean: 227.45). Atrazine, its degradates deethyl atrazine (DEA) and deisopropyl atrazine (DIA), trifluralin and butachlor were the most frequently detected herbicides, while DEA, clomazone, nicosulfuron, fomesafen, and mefenacet exhibited the highest concentrations. Despite being less frequently reported in Chinese soils, fomesafen, nicosulfuron, clomazone, and mefenacet were found widely present. Although most of the compounds posed a minimal or low ecological risk, atrazine, nicosulfuron and DEA exhibited medium to high potential risks. The key factors identified to regulate the fate of herbicides were soil chemical properties, amount of herbicides application, and the crop type. The soybean soils showed highest herbicide residues, while the soil mineral contents likely adsorbed more herbicides. This study provides a valuable large-scale dataset of herbicide residues across the entire Mollisols region of China along with fine-scale characterization of the ecological risks. Mitigation and management measures are needed to reduce the herbicide inputs and residues in the region.

A review of organophosphonates, their natural and anthropogenic sources, environmental fate and impact on microbial greenhouse gases emissions - Identifying knowledge gaps

Organophosphonates (OPs) are a unique group of natural and synthetic compounds, characterised by the presence of a stable, hard-to-cleave bond between the carbon and phosphorus atoms. OPs exhibit high resistance to abiotic degradation, excellent chelating properties and high biological activity. Despite the huge and increasing scale of OP production and use worldwide, little is known about their transportation and fate in the environment. Available data are dominated by information concerning the most recognised organophosphonate - the herbicide glyphosate - while other OPs have received little attention. In this paper, a comprehensive review of the current state of knowledge about natural and artificial OPs is presented (including glyphosate). Based on the available literature, a number of knowledge gaps have been identified that need to be filled in order to understand the environmental effects of these abundant compounds. Special attention has been given to GHG-related processes, with a particular focus on CH4. This stems from the recent discovery of OP-dependent CH4 production in aqueous environments under aerobic conditions. The process has changed the perception of the biogeochemical cycle of CH4, since it was previously thought that biological methane formation was only possible under anaerobic conditions. However, there is a lack of knowledge on whether OP-associated methane is also formed in soils. Moreover, it remains unclear whether anthropogenic OPs affect the CH4 cycle, a concern of significant importance in the context of the increasing rate of global warming. The literature examined in this review also calls for additional research into the date of OPs in waste and sewage and in their impact on environmental microbiomes.

Glyphosate (Roundup) as phosphorus nutrient enhances carbon and nitrogen accumulation and up-regulates phosphorus metabolisms in the haptophyte Isochrysis galbana

Inorganic phosphate limitation for phytoplankton may be intensified with water stratification by global warming, and with the increasing nitrogen: phosphorus (N:P) ratio in coastal zones resulting from continuous anthropogenic N overloading. Under these circumstances, phytoplankton's ability to use dissolved organic phosphorus (DOP) will give species a competitive advantage. In our previous study, we have shown that the haptophyte Isochrysis galbana can use glyphosate (Roundup) as a P nutrient source to support growth, but the mechanism of how remains unexplored. Here, we show that three genes encoding PhnC (IgPhnCs), which exhibit up-regulated expression in glyphosate-grown cultures, are probably responsible for glyphosate uptake, while homologs of PhnK and PhnL (IgPhnK and IgPhnL) probably provide auxiliary support for the intracellular degradation of glyphosate. Meanwhile, we found the use efficiency of glyphosate was low compared with phosphate, probably because glyphosate uptake and hydrolysis cost energy and because glyphosate induces oxidative stress in I. galbana. Meanwhile, genes encoding 5-enolpyruvylshikimate 3-phosphate (EPSP) synthase, the target of the herbicide, were up-regulated in glyphosate cultures. Furthermore, our data showed the up-regulation of P metabolisms (transcription) in glyphosate-grown cultures, which further induced the up-regulation of nitrate/nitrite transport and biosynthesis of some amino acids. Meanwhile, glyphosate-grown cells accumulated more C and N, resulting in remarkably high C:N:P ratio, and this, along with the up-regulated P metabolisms, was under transcriptional and epigenetic regulation. This study sheds lights on the mechanism of glyphosate utilization as a source of P nutrient by I. galbana, and these findings have biogeochemical implications.

Impact of glyphosate and glyphosate-based herbicides on phyllospheric Methylobacterium

Symbiotic Methylobacterium comprise a significant portion of the phyllospheric microbiome, and are known to benefit host plant growth, development, and confer tolerance to stress factors. The near ubiquitous use of the broad-spectrum herbicide, glyphosate, in farming operations globally has necessitated a more expansive evaluation of the impacts of the agent itself and formulations containing glyphosate on important components of the plant phyllosphere, including Methylobacterium.This study provides an investigation of the sensitivity of 18 strains of Methylobacterium to glyphosate and two commercially available glyphosate-based herbicides (GBH). Nearly all strains of Methylobacterium showed signs of sensitivity to the popular GBH formulations WeatherMax® and Transorb® in a modified Kirby Bauer experiment. However, exposure to pure forms of glyphosate did not show a significant effect on growth for any strain in both the Kirby Bauer test and in liquid broth, until polysorbate-20 (Tween20) was added as a surfactant. Artificially increasing membrane permeability through the introduction of polysorbate-20 caused a 78-84% reduction in bacterial cell biomass relative to controls containing glyphosate or high levels of surfactant only (0-9% and 6-37% reduction respectively). Concentrations of glyphosate as low as 0.05% w/v (500 µg/L) from both commercial formulations tested, inhibited the culturability of Methylobacterium on fresh nutrient-rich medium.To better understand the compatibility of important phyllospheric bacteria with commercial glyphosate-based herbicides, this study endeavours to characterize sensitivity in multiple strains of Methylobacterium, and explore possible mechanisms by which toxicity may be induced.

Elucidation of the role of metals in the adsorption and photodegradation of herbicides by metal-organic frameworks

Here, four MOFs, namely Sc-TBAPy, Al-TBAPy, Y-TBAPy, and Fe-TBAPy (TBAPy: 1,3,6,8-tetrakis(p-benzoic acid)pyrene), were characterized and evaluated for their ability to remediate glyphosate (GP) from water. Among these materials, Sc-TBAPy demonstrates superior performance in both the adsorption and degradation of GP. Upon light irradiation for 5 min, Sc-TBAPy completely degrades 100% of GP in a 1.5 mM aqueous solution. Femtosecond transient absorption spectroscopy reveals that Sc-TBAPy exhibits enhanced charge transfer character compared to the other MOFs, as well as suppressed formation of emissive excimers that could impede photocatalysis. This finding was further supported by hydrogen evolution half-reaction (HER) experiments, which demonstrated Sc-TBAPy's superior catalytic activity for water splitting. In addition to its faster adsorption and more efficient photodegradation of GP, Sc-TBAPy also followed a selective pathway towards the oxidation of GP, avoiding the formation of toxic aminomethylphosphonic acid observed with the other M3+-TBAPy MOFs. To investigate the selectivity observed with Sc-TBAPy, electron spin resonance, depleted oxygen conditions, and solvent exchange with D2O were employed to elucidate the role of different reactive oxygen species on GP photodegradation. The findings indicate that singlet oxygen (1O2) plays a critical role in the selective photodegradation pathway achieved by Sc-TBAPy.

Systemic Analysis of Glyphosate Impact on Environment and Human Health

With a growing global population, agricultural scientists are focusing on crop production management and the creation of new strategies for a higher agricultural output. However, the growth of undesirable plants besides the primary crop poses a significant challenge in agriculture, necessitating the massive application of herbicides to eradicate this problem. Several synthetic herbicides are widely utilized, with glyphosate emerging as a potential molecule for solving this emerging issue; however, it has several environmental and health consequences. Several weed species have evolved resistance to this herbicide, therefore lowering agricultural yield. The persistence of glyphosate residue in the environment, such as in water and soil systems, is due to the misuse of glyphosate in agricultural regions, which causes its percolation into groundwater via the vertical soil profile. As a result, it endangers many nontarget organisms existing in the natural environment, which comprises both soil and water. The current Review aims to provide a systemic analysis of glyphosate, its various effects on the environment, its subsequent impact on human health and animals, which will lead us toward a better understanding of the issues about herbicide usage and aid in managing it wisely, as in the near the future glyphosate market is aiming for a positive forecast until 2035.

Biomonitoring of glyphosate and aminomethylphosphonic acid: Current insights and future perspectives

Glyphosate is one of the most widely used herbicides globally, raising concerns about its potential impact on human health. Biomonitoring studies play a crucial role in assessing human exposure to glyphosate and providing valuable insights into its distribution and metabolism in the body. This review aims to summarize the current trends and future perspectives in biomonitoring of glyphosate and its major degradation product of aminomethylphosphonic acid (AMPA). A comprehensive literature search was conducted, focusing on studies published between January 2000 and December 2022. The findings demonstrated that glyphosate and AMPA have been reported in different human specimens with urine as the dominance. Sample pretreatment techniques of solid-phase and liquid-liquid extractions coupled with liquid/gas chromatography-tandem mass spectrometry have achieved matrix elimination and accurate analysis. We also examined and compared the exposure characteristics of these compounds among different regions and various populations, with significantly higher levels of glyphosate and AMPA observed in Asian populations and among occupational groups. The median urinary concentration of glyphosate in children was 0.54 ng/mL, which was relatively higher than those in women (0.28 ng/mL) and adults (0.12 ng/mL). It is worth noting that children may exhibit increased susceptibility to glyphosate exposure or have different exposure patterns compared to women and adults. A number of important perspectives were proposed in order to further facilitate the understanding of health effects of glyphosate and AMPA, which include, but are not limited to, method standardization, combined exposure assessment, attention for vulnerable populations, long-term exposure effects and risk communication and public awareness.

Fate of glyphosate in lakes with varying trophic levels and its modification by root exudates of submerged macrophytes

Accelerated eutrophication in lakes reduces the number of submerged macrophytes and alters the residues of glyphosate and its degradation products. However, the effects of submerged macrophytes on the fate of glyphosate remain unclear. We investigated eight lakes with varying trophic levels along the middle and lower reaches of the Yangtze River in China, of which five lakes contained either glyphosate or aminomethylphosphate (AMPA). Glyphosate and AMPA residues were significantly positively correlated with the trophic levels of lakes (P < 0.01). In lakes, glyphosate is degraded through the AMPA and sarcosine pathways. Eight shared glyphosate-degrading enzymes and genes were observed in different lake sediments, corresponding to 44 degrading microorganisms. Glyphosate concentrations in sediments were significantly higher in lakes with lower abundances of soxA (sarcosine oxidase) and soxB (sarcosine oxidase) (P < 0.05). In the presence of submerged macrophytes, oxalic and malonic acids secreted by the roots of submerged macrophytes increased the abundance of glyphosate-degrading microorganisms containing soxA or soxB (P < 0.05). These results revealed that a decrease in the number of submerged macrophytes in eutrophic lakes may inhibit glyphosate degradation via the sarcosine pathway, leading to a decrease in glyphosate degradation and an increase in glyphosate residues.

Effect of temperature on the degradation of glyphosate by Mn-oxide: Products and pathways of degradation

Glyphosate is the most commonly used herbicide in the United States. In the environment, glyphosate residues can either degrade into more toxic and persistent byproducts such as aminomethylphosphonic acid (AMPA) or environmentally benign species such as sarcosine or glycine. In this research, the birnessite-catalyzed degradation of glyphosate was studied under environmentally relevant temperatures (10-40 °C) using high-performance liquid chromatography, inductively coupled plasma mass spectrometry, nuclear magnetic resonance, and theoretical calculations. Our results show a temperature-dependent degradation pathway preference for AMPA and glycine production. The AMPA and glycine pathways are competitive at short reaction times, but the glycine pathway became increasingly preferred as reaction time and temperature increased. The measured free energy barriers are comparable for both the glycine and AMPA pathways (93.5 kJ mol-1 for glycine and 97.1 kJ mol-1 for AMPA); however, the entropic energy penalty for the AMPA pathway is significantly greater than the glycine pathway (-TΔS‡ = 26.2 and 42.8 kJ mol-1 for glycine and AMPA, respectively). These findings provide possible routes for biasing glyphosate degradation towards safer products, thus to decrease the overall environmental toxicity.

Recent technologies for glyphosate removal from aqueous environment: A critical review

The growing demand for food has led to an increase in the use of herbicides and pesticides over the years. One of the most widely used herbicides is glyphosate (GLY). It has been used extensively since 1974 for weed control and is currently classified by the World Health Organization (WHO) as a Group 2A substance, probably carcinogenic to humans. The industry and academia have some disagreements regarding GLY toxicity in humans and its effects on the environment. Even though this herbicide is not mentioned in the WHO water guidelines, some countries have decided to set maximum acceptable concentrations in tap water, while others have decided to ban its use in crop production completely. Researchers around the world have employed different technologies to remove or degrade GLY, mostly at the laboratory scale. Water treatment plants combine different technologies to remove it alongside other water pollutants, in some cases achieving acceptable removal efficiencies. Certainly, there are many challenges in upscaling purification technologies due to the costs and lack of factual information about their adverse effects. This review presents different technologies that have been used to remove GLY from water since 2012 to date, its detection and removal methods, challenges, and future perspectives.

Glyphosate spraying exacerbates nitrogen and phosphorus loss in karst slope farmland

Glyphosate herbicide is an indispensable material in agricultural production. In order to explore the potential environmental effects of glyphosate application in karst slope farmland, this paper used a variable slope steel tank to simulate the surface microtopography and underground pore structure characteristics of karst slope farmland, and combined with artificial rainfall experiments to explore the migration path of glyphosate in karst slope farmland and the impact of spraying glyphosate on soil nitrogen and phosphorus loss. The results showed that under the condition of heavy rain, glyphosate in karst slope farmland was mainly transported and diffused by surface runoff, supplemented by underground runoff; secondly, in different hydrological paths, glyphosate directly affected the content of nitrogen and phosphorus in runoff, and all showed extremely significant positive correlation (p < 0.001). In addition, rainfall conditions such as rainfall intensity, rainfall duration, and runoff affected the content of nitrogen and phosphorus in runoff to varying degrees. In conclusion, the application of glyphosate significantly increased the content of nitrogen and phosphorus in different runoff and accelerated the loss of nitrogen and phosphorus from soil, which not only led to soil degradation, but also threatened the safety of aquatic ecosystem. Therefore, in the prevention and control of agricultural non-point source pollution, the threat of glyphosate to the surrounding aquatic ecosystem cannot be ignored, especially in karst areas with frequent rainstorms and serious water erosion, long-term monitoring and risk assessment of glyphosate are needed.

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.

Glyphosate has a negligible impact on bacterial diversity and dynamics during composting

The herbicide glyphosate has several potential entry points into composting sites and its impact on composting processes has not yet been evaluated. To assess its impact on bacterial diversity and abundance as well as on community composition and dynamics, we conducted a mesocosm experiment at the Montreal Botanical Garden. Glyphosate had no effect on physicochemical property evolution during composting, while it was completely dissipated by the end of the experiment. Sampling at Days 0, 2, 28 and 112 of the process followed by 16S rRNA amplicon sequencing also found no effect of glyphosate on species richness and community composition. Differential abundance analyses revealed an increase of a few taxa in the presence of glyphosate, namely TRA3-20 (order Polyangiales), Pedosphaeraceae and BIrii41 (order Burkholderiales) after 28 days. In addition, five amplicon sequence variants (ASVs) had lower relative abundance in the glyphosate treatment compared to the control on Day 2, namely Comamonadaceae, Pseudomonas sp., Streptomyces sp., Thermoclostridium sp. and Actinomadura keratinilytica, while two ASVs were less abundant on Day 112, namely Pedomicrobium sp. and Pseudorhodoplanes sp. Most differences in abundance were measured between the different sampling points within each treatment. These results present glyphosate as a poor determinant of species recruitment during composting.

Glyphosate in the environment: interactions and fate in complex soil and water settings, and (phyto) remediation strategies

Glyphosate (Gly) and its formulations are broad-spectrum herbicides globally used for pre- and post-emergent weed control. Glyphosate has been applied to terrestrial and aquatic ecosystems. Critics have claimed that Gly-treated plants have altered mineral nutrition and increased susceptibility to plant pathogens because of Gly ability to chelate divalent metal cations. Still, the complete resistance of Gly indicates that chelation of metal cations does not play a role in herbicidal efficacy or have a substantial impact on mineral nutrition. Due to its extensive and inadequate use, this herbicide has been frequently detected in soil (2 mg kg-1, European Union) and in stream water (328 µg L-1, USA), mostly in surface (7.6 µg L-1, USA) and groundwater (2.5 µg L-1, Denmark). International Agency for Research on Cancer (IARC) already classified Gly as a category 2 A carcinogen in 2016. Therefore, it is necessary to find the best degradation techniques to remediate soil and aquatic environments polluted with Gly. This review elucidates the effects of Gly on humans, soil microbiota, plants, algae, and water. This review develops deeper insight toward the advances in Gly biodegradation using microbial communities. This review provides a thorough understanding of Gly interaction with mineral elements and its limitations by interfering with the plants biochemical and morphological attributes.

How Benthic Sediment Microbial Communities Respond to Glyphosate and Its Metabolite: a Microcosm Experiment

Glyphosate is the most commonly used agricultural herbicide in the world. In aquatic ecosystems, glyphosate often adsorbs to benthic substrates or is metabolized and degraded by microorganisms. The effects of glyphosate on microbial communities vary widely as microorganisms respond differently to exposure. To help understand the impacts of glyphosate on the sediment microbiome, we conducted a microcosm experiment examining the responses of benthic sediment microbial communities to herbicide treatments. Sediments from a prairie pothole wetland were collected, and 16S rRNA gene sequencing was used to analyze community composition 2-h and 14-days after a single treatment of low (0.07 ppm), medium (0.7 ppm), or high (7 ppm) glyphosate, aminomethylphosphonic acid (glyphosate metabolite), or a glyphosate-based commercial formula. We found no significant differences in microbial community composition across treatments, concentration levels, or day of sampling. These findings suggest that microbial species in the Prairie Pothole Region of North America may be tolerant to glyphosate exposure.

Application of Highly Sensitive Immunosensor Based on Optical Waveguide Light-Mode Spectroscopy (OWLS) Technique for the Detection of the Herbicide Active Ingredient Glyphosate

The herbicide active ingredient glyphosate is the most widely applied herbicidal substance worldwide. Currently it is the market-leading pesticide, and its use is projected to further grow 4.5-fold between 2022 and 2029. Today, glyphosate use exceeds one megaton per year worldwide, which represents a serious environmental burden. A factor in the overall boost in the global use of glyphosate has been the spread of glyphosate-tolerant genetically modified (GM) crops that allow post-emergence applications of the herbicide on these transgenic crops. In turn, cultivation of glyphosate-tolerant GM crops represented 56% of the glyphosate use in 2019. Due to its extremely high application rate, xenobiotic behaviour and a water solubility (11.6 mg/mL at 25 °C) unusually high among pesticide active ingredients, glyphosate has become a ubiquitous water pollutant and a primary drinking water contaminant worldwide, presenting a threat to water quality. The goal of our research was to develop a rapid and sensitive method for detecting this herbicide active ingredient. For this purpose, we applied the novel analytical biosensor technique optical waveguide light-mode spectroscopy (OWLS) to the label-free detection of glyphosate in a competitive immunoassay format using glyphosate-specific polyclonal antibodies. After immobilising the antigen conjugate in the form of a glyphosate conjugated to human serum albumin for indirect measurement, the sensor chip was used in a flow-injection analyser system. For the measurements, an antibody stock solution was diluted to 2.5 µg/mL. During the measurement, standard solutions were mixed with the appropriate concentration of antibodies and incubated for 1 min before injection. The linear detection range and the EC50 value of the competitive detection method were between 0.01 and 100 ng/mL and 0.60 ng/mL, respectively. After investigating the indirect method, we tested the cross-reactivity of the antibody with glyphosate and structurally related compounds.

Insights into the metabolic pathways and biodegradation mechanisms of chloroacetamide herbicides

Chloroacetamide herbicides are widely used around the world due to their high efficiency, resulting in increasing levels of their residues in the environment. Residual chloroacetamides and their metabolites have been frequently detected in soil, water and organisms and shown to have toxic effects on non-target organisms, posing a serious threat to the ecosystem. As such, rapid and efficient techniques that eliminate chloroacetamide residues from the ecosystem are urgently needed. Degradation of these herbicides in the environment mainly occurs through microbial metabolism. Microbial strains such as Acinetobacter baumannii DT, Bacillus altitudinis A16, Pseudomonas aeruginosa JD115, Sphingobium baderi DE-13, Catellibacterium caeni DCA-1, Stenotrophomonas acidaminiphila JS-1, Klebsiella variicola B2, and Paecilomyces marquandii can effectively degrade chloroacetamide herbicides. The degradation pathway of chloroacetamide herbicides in aerobic bacteria is mainly initiated by an N/C-dealkylation reaction, followed by aromatic ring hydroxylation and cleavage processes, whereas dechlorination is the initial reaction in anaerobic bacteria. The molecular mechanisms associated with bacterial degradation of chloroacetamide herbicides have been explored, with amidase, hydrolase, reductase, ferredoxin and cytochrome P450 oxygenase currently known to play a pivotal role in the catabolic pathways of chloroacetamides. The fungal pathway for the degradation of these herbicides is more complex with more diversified products, and the degradation enzymes and genes involved remain to be discovered. However, there are few reviews specifically summarizing the microbial degrading species and biochemical mechanisms of chloroacetamide herbicides. Here, we briefly summarize the latest progress resulting from research on microbial strain resources and enzymes involved in degradation of these herbicides and their corresponding genes. Furthermore, we explore the biochemical pathways and molecular mechanisms for biodegradation of chloroacetamide herbicides in depth, thereby providing a reference for further research on the bioremediation of such herbicides.

Urinary glyphosate and AMPA levels in a cross-sectional study of postmenopausal women: Associations with organic eating behavior and dietary intake

Animal and epidemiologic studies suggest that there may be adverse health effects from exposure to glyphosate, the most highly used pesticide in the world, and its metabolite aminomethylphosphonic acid (AMPA). Meanwhile, consumption of organic foods (presumably grown free of chemical pesticides) has increased in recent years. However, there have been limited biomonitoring studies assessing the levels of human glyphosate and AMPA exposure in the United States. We examined urinary levels of glyphosate and AMPA in the context of organic eating behavior in a cohort of healthy postmenopausal women residing in Southern California and evaluated associations with demographics, dietary intake, and other lifestyle factors. 338 women provided two first-morning urine samples and at least one paired 24-h dietary recall reporting the previous day's dietary intake. Urinary glyphosate and AMPA were measured using LC-MS/MS. Participants reported on demographic and lifestyle factors via questionnaires. Potential associations were examined between these factors and urinary glyphosate and AMPA concentrations. Glyphosate was detected in 89.9% of urine samples and AMPA in 67.2%. 37.9% of study participants reported often or always eating organic food, 30.2% sometimes, and 32.0% seldom or never. Frequency of organic food consumption was associated with several demographic and lifestyle factors. Frequent organic eaters had significantly lower urinary glyphosate and AMPA levels, but not after adjustment for covariates. Grain consumption was significantly associated with higher urinary glyphosate levels, even among women who reported often or always eating organic grains. Soy protein and alcohol consumption as well as high frequency of eating fast food were associated with higher urinary AMPA levels. In conclusion, in the largest study to date examining paired dietary recall data and measurements of first-void urinary glyphosate and AMPA, the vast majority of subjects sampled had detectable levels, and significant dietary sources in the American diet were identified.

Hazardous impacts of glyphosate on human and environment health: Occurrence and detection in food

With the ever-increasing human population, farming lands are decreasing every year, therefore, for effective crop management; agricultural scientists are continually developing new strategies. However, small plants and herbs always impart a much loss in the yields of the crop and farmers are using tons of herbicides to eradicate that problem. Across the world, several herbicides are available in the market for effective crop management, however, scientists observed various environmental and health effects of the herbicides. Over the past 40 years, the herbicide glyphosate has been used extensively with the assumption of negligible effects on the environment and human health. However, in recent years, concerns have increased globally about the potential direct and indirect effects on human health due to the excessive use of glyphosate. As well, the toxicity on ecosystems and the possible effects on all living creatures have long been at the center of a complex discrepancy about the authorization for its use. The World Health Organization also further classified glyphosate as a carcinogenic toxic component and it was banned in 2017 due to numerous life-threatening side effects on human health. In the present era, the residues of banned glyphosate are more prevalent in agricultural and environmental samples which are directly affecting human health. Various reports revealed the detailed extraction process of glyphosate from different categories of the food matrix. Therefore, in the present review, to reveal the importance of glyphosate monitoring in the food matrix, we discussed the environmental and health effects of glyphosate with acute toxicity levels. Also, the effect of glyphosate on aquatic life is discussed in detail and various detection methods such as fluorescence, chromatography, and colorimetric techniques from different food samples with a limit of detection values are revealed. Overall, this review will give an in-depth insight into the various toxicological aspects and detection of glyphosate from food matrix using various advanced analytical techniques.

Application of a novel hybrid MIL-53(Al)@rice husk for the adsorption of glyphosate in water: Characteristics and mechanism of the process

The development of new materials that have a high capacity to remove pollutants in water-based media is becoming increasingly important because of the serious contamination of water and the negative impact on biodiversity and public health. The presence of glyphosate in water, the most widely used herbicide worldwide, has triggered alerts owing to the collateral effects it may cause on human health. The main objective of the present study was to investigate the potential of the hybrid material MIL-53(Al)@RH for the adsorption of glyphosate in aqueous solution. The material was obtained following the methodology of MIL-53(Al) synthesis in the presence of hydrolyzed rice husk assisted by microwave. Batch adsorption experiments were carried out to evaluate the adsorbent dosage, pH₀ solution effect, contact time, adsorbate concentration, and temperature effect. The results demonstrated that a maximum adsorption capacity of 296.95 mg g^-1, at pH₀ 4 with a ratio of 0.04 g MIL-53(Al)@RH/50 mL of solution, was achieved in 30 min. The Avrami and pseudo-second order models appropriately described the adsorption kinetics and the equilibrium by Langmuir and Sips models. The enthalpy changes (ΔH°) determined propose an endothermic reaction governed by chemisorption, corroborating the kinetic and equilibrium settings. Hydrogen bonds, π*-π interactions, and complexation between the metal centers of MIL-53(Al) and the anionic groups of glyphosate were postulated to be involved as adsorption mechanisms. Finally, for practical application, MIL-53(Al)@RH was packed in a column for a fixed-bed test which revealed that the hybrid can remove glyphosate with an adsorption capacity of 76.304 mg L^-1, utilizing 90% of the bed.

The role of land use, management, and microbial diversity depletion on glyphosate biodegradation in tropical soils

Land use and management changes affect the composition and diversity of soil bacteria and fungi, which in turn may alter soil health and the provision of key ecological functions, such as pesticide degradation and soil detoxification. However, the extent to which these changes affect such services is still poorly understood in tropical agroecosystems. Our main goal was to evaluate how land-use (tilled versus no-tilled soil), soil management (N-fertilization), and microbial diversity depletion [tenfold (D1 = 10^-1) and thousandfold (D3 = 10^-3) dilutions] impacted soil enzyme activities (β-glycosidase and acid phosphatase) involved in nutrient cycles and glyphosate mineralization. Soils were collected from a long-term experimental area (35 years) and compared to its native forest soil (NF). Glyphosate was selected due to its intensive use in agriculture worldwide and in the study area, as well as its recalcitrance in the environment by forming inner sphere complexes. Bacterial communities played a more important role than the fungi in glyphosate degradation. For this function, the role of microbial diversity was more critical than land use and soil management. Our study also revealed that conservation tillage systems, such as no-tillage, regardless of nitrogen fertilizer use, mitigates the negative effects of microbial diversity depletion, being more efficient and resilient regarding glyphosate degradation than conventional tillage systems. No-tilled soils also presented much higher β-glycosidase and acid phosphatase activities as well as higher bacterial diversity indexes than those under conventional tillage. Consequently, conservation tillage is a key component for sustaining soil health and its functionality, providing critical ecosystem functions, such as soil detoxification in tropical agroecosystems.

Livestock and poultry farm wastewater treatment and its valorization for generating value-added products: Recent updates and way forward

Livestock and poultry wastewater poses a potent risk factor for environmental pollution accelerating disease load and premature deaths. It is characterized by high chemical oxygen demand, biological oxygen demand, suspended solids, heavy metals, pathogens, and antibiotics, among other contaminants. These contaminants have a negative impact on the quality of soil, groundwater, and air, and is a potential hazard to human health. Depending on the specific characteristics of wastewater, such as the type and concentration of pollutants present; several physical, chemical and biological strategies have been developed for wastewater treatment. This review aims at providing comprehensive overview of the profiling of livestock wastewater from the dairy, swine and poultry sub-sectors along with the biological (annamox and genetically modified bacteria) and physico-chemical treatment methodologies, and valorisation for the generation of value-added products such as bioplastics, biofertilizers, biohydrogen and microalgal-microbial fuel cells. Additionally, future perspectives for efficient and sustainable wastewater treatment are contemplated.

Cellular Response and Molecular Mechanism of Glyphosate Degradation by Chryseobacterium sp. Y16C

Glyphosate is one of the most widely used herbicides worldwide. Unfortunately, the continuous use of glyphosate has resulted in serious environmental contamination and raised public concern about its impact on human health. In our previous study, Chryseobacterium sp. Y16C was isolated and characterized as an efficient degrader that can completely degrade glyphosate. However, the biochemical and molecular mechanisms underlying its glyphosate biodegradation ability remain unclear. In this study, the physiological response of Y16C to glyphosate stimulation was characterized at the cellular level. The results indicated that, in the process of glyphosate degradation, Y16C induced a series of physiological responses in the membrane potential, reactive oxygen species levels, and apoptosis. The antioxidant system of Y16C was activated to alleviate the oxidative damage caused by glyphosate. Furthermore, a novel gene, goW, was expressed in response to glyphosate. The gene product, GOW, is an enzyme that catalyzes glyphosate degradation, with putative structural similarities to glycine oxidase. GOW encodes 508 amino acids, with an isoelectric point of 5.33 and a molecular weight of 57.2 kDa, which indicates that it is a glycine oxidase. GOW displays maximum enzyme activity at 30 °C and pH 7.0. Additionally, most of the metal ions exhibited little influence on the enzyme activity except for Cu²⁺. Finally, with glyphosate as the substrate, the catalytic efficiency of GOW was higher than that of glycine, although opposite results were observed for the affinity. Taken together, the current study provides new insights to deeply understand and reveal the mechanisms of glyphosate degradation in bacteria.

Detoxification and metabolism of glyphosate by a Pseudomonas sp. via biogenic manganese oxidation

Biogenic manganese oxides (BMO) are widely distributed in groundwater and provides promise for adsorbing and oxidizing a wide range of micropollutants, however, the continuous biodegradation and bioavailability of micropollutants via cycle biogenic Mn(II) oxidation remains to be elucidated. In this study, glyphosate was degraded and to serve as the nutrient source by a Pseudomonas sp. QJX-1. The addition of glyphosate will not affect the Mn(II) oxidation function of the strain but will affect its Mn(II) oxidation process and effect. The glyphosate degradation products could further be used as the C, N and P sources for bacterium growth. Analysis of the RNA-seq data suggested that Mn(II) oxidation driven by oxidoreductases for glyphosate degradation. The long-term column experiments using biological Mn(II) cycling to realize continuous detoxification and metabolism of glyphosate, and thus revealed the synergism effects of biological and chemical conversion on toxic micropollutants and continuous metabolism in an aquatic ecosystem.

Fate of glyphosate and its degradation products AMPA, glycine and sarcosine in an agricultural soil: Implications for environmental risk assessment

Glyphosate can be biodegraded via the aminomethylphosponic acid (AMPA) and the sarcosine/glycine pathway leading to the formation of three intermediate products AMPA, sarcosine or glycine. The fate of the three intermediate compounds of glyphosate biodegradation including nature of non-extractable residues (NERs; harmless biogenic [NERs_biogenic] versus hazardous xenobiotic [NERs_xenobiotic]) in soils has not been investigated yet. This information is crucial for an assessment of environmental risks related to the speciation of glyphosate-derived NERs which may stem from glyphosate intermediates. Therefore, we incubated ¹³C- and ¹⁵N-labeled glyphosate (2-¹³C,¹⁵N-glyphosate) and its degradation product AMPA (¹³C,¹⁵N-AMPA), sarcosine (¹³C₃,¹⁵N-sarcosine) or glycine (¹³C₂,¹⁵N-glycine) in an agricultural soil separately for a period of 75 days. ¹³C₂-glycine and ¹³C₃-sarcosine mineralized rapidly compared to 2-¹³C-glyphosate and ¹³C-AMPA. The mineralization of ¹³C-AMPA was lowest among all four compounds due to its persistent nature. Only 0.5% of the initially added 2-¹³C,¹⁵N-glyphosate and still about 30% of the initially added ¹³C,¹⁵N-AMPA was extracted from soil after 75 days. The NERs formed from ¹³C,¹⁵N-AMPA were mostly NERs_xenobiotic as compared to other three compounds for which significant amounts of NERs_biogenic were determined. We noticed 2-¹³C,¹⁵N-glyphosate was biodegraded via two biodegradation pathways simultaneously; however, the sarcosine/glycine pathway with the formation of harmless NERs_biogenic presumably dominated.

Bioremediation of the herbicide glyphosate in polluted soils by plant-associated microbes

Most productive lands worldwide base their crop production on the use of glyphosate (GLY)-resistant plants, and consequently, widespread use of this herbicide has led to environmental issues that need to be solved. Soil bioremediation technologies based on degradation of GLY by microorganisms are strategies that have been considered useful to solve this environmental problem. Recently, a further step has been taken considering the use of bacteria that interact with plants, either alone or both bacteria and plant together, for the removal of GLY herbicide. Plant-interacting microorganisms with plant growth-promoting traits can also enhance plant growth and contribute to successful bioremediation strategies.

Characterization of a New Pseudomonas Putida Strain Ch2, a Degrader of Toxic Anthropogenic Compounds Epsilon-Caprolactam and Glyphosate

In this work, a new Ch2 strain was isolated from soils polluted by agrochemical production wastes. This strain has a unique ability to utilize toxic synthetic compounds such as epsilon-caprolactam (CAP) as a sole carbon and energy source and the herbicide glyphosate (GP) as a sole source of phosphorus. Analysis of the nucleotide sequence of the 16S rRNA gene of Ch2 revealed that the strain belongs to the species Pseudomonas putida. This strain grew in the mineral medium containing CAP in a concentration range of 0.5 to 5.0 g/L and utilized 6-aminohexanoic acid and adipic acid, which are the intermediate products of CAP catabolism. The ability of strain Ch2 to degrade CAP is determined by a conjugative megaplasmid that is 550 kb in size. When strain Ch2 is cultured in a mineral medium containing GP (500 mg/L), more intensive utilization of the herbicide occurs in the phase of active growth. In the phase of declining growth, there is an accumulation of aminomethylphosphonic acid, which indicates that the C-N bond is the first site cleaved during GP degradation (glyphosate oxidoreductase pathway). Culture growth in the presence of GP during the early step of its degradation is accompanied by unique substrate-dependent changes in the cytoplasm, including the formation of vesicles of cytoplasmic membrane consisting of specific electron-dense content. There is a debate about whether these membrane formations are analogous to metabolosomes, where the primary degradation of the herbicide can take place. The studied strain is notable for its ability to produce polyhydroxyalkanoates (PHAs) when grown in mineral medium containing GP. At the beginning of the stationary growth phase, it was shown that, the amount and size of PHA inclusions in the cells drastically increased; they filled almost the entire volume of cell cytoplasm. The obtained results show that the strain P. putida Ch2 can be successfully used for the PHAs’ production. Moreover, the ability of P. putida Ch2 to degrade CAP and GP determines the prospects of its application for the biological cleanup of CAP production wastes and in situ bioremediation of soil polluted with GP.

Effective Removal of Glyphosate from Aqueous Systems Using Synthesized PEG-Coated Calcium Peroxide Nanoparticles: Kinetics Study, H2O2 Release Performance and Degradation Pathways

Glyphosate (N-phosphonomethyl glycine) is a non-selective, broad-spectrum organophosphate herbicide. Its omnipresent application with large quantity has made glyphosate as a problematic contaminant in water. Therefore, an effective technology is urgently required to remove glyphosate and its metabolites from water. In this study, calcium peroxide nanoparticles (nCPs) were functioned as an oxidant to produce sufficient hydroxyl free radicals (·OH) with the presence of Fe²⁺ as a catalyst using a Fenton-based system. The nCPs with small particle size (40.88 nm) and high surface area (28.09 m²/g) were successfully synthesized via a co-precipitation method. The synthesized nCPs were characterized using transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), Brunauer-Emmett-Teller analysis (BET), dynamic light scattering (DLS), and field emission scanning electron microscopy (FESEM) techniques. Under the given conditions (pH = 3.0, initial nCPs dosage = 0.2 g, Ca²⁺/Fe²⁺ molar ratio = 6, the initial glyphosate concentration = 50 mg/L, RT), 99.60% total phosphorus (TP) removal and 75.10% chemical oxygen demand (COD) removal were achieved within 75 min. The degradation process fitted with the Behnajady-Modirshahla-Ghanbery (BMG) kinetics model. The H₂O₂ release performance and proposed degradation pathways were also reported. The results demonstrated that calcium peroxide nanoparticles are an efficient oxidant for glyphosate removal from aqueous systems.

Environmental occurrence, toxicity concerns, and biodegradation of neonicotinoid insecticides

Neonicotinoids (NEOs) are fourth generation pesticides, which emerged after organophosphates, pyrethroids, and carbamates and they are widely used in vegetables, fruits, cotton, rice, and other industrial crops to control insect pests. NEOs are considered ideal substitutes for highly toxic pesticides. Multiple studies have reported NEOs have harmful impacts on non-target biological targets, such as bees, aquatic animals, birds, and mammals. Thus, the remediation of neonicotinoid-sullied environments has gradually become a concern. Microbial degradation is a key natural method for eliminating neonicotinoid insecticides, as biodegradation is an effective, practical, and environmentally friendly strategy for the removal of pesticide residues. To date, several neonicotinoid-degrading strains have been isolated from the environment, including Stenotrophomonas maltophilia, Bacillus thuringiensis, Ensifer meliloti, Pseudomonas stutzeri, Variovorax boronicumulans, and Fusarium sp., and their degradation properties have been investigated. Furthermore, the metabolism and degradation pathways of neonicotinoids have been broadly detailed. Imidacloprid can form 6-chloronicotinic acid via the oxidative cleavage of guanidine residues, and it is then finally converted to non-toxic carbon dioxide. Acetamiprid can also be demethylated to remove cyanoimine (=N-CN) to form a less toxic intermediate metabolite. A few studies have discussed the neonicotinoid toxicity and microbial degradation in contaminated environments. This review is focused on providing an in-depth understanding of neonicotinoid toxicity, microbial degradation, catabolic pathways, and information related to the remediation process of NEOs. Future research directions are also proposed to provide a scientific basis for the risk assessment and removal of these pesticides.

Stoichiometric stability of aquatic organisms increases with trophic level under warming and eutrophication

The balance of stoichiometric traits of organisms is crucial for nutrient cycling and energy flow in ecosystems. However, the impacts of different drivers on stoichiometric (carbon, C; nitrogen, N; and phosphorus, P) variations of organisms have not been well addressed. In order to understand how stoichiometric traits vary across trophic levels under different environmental stressors, we performed a mesocosm experiment to explore the impacts of warming (including +3 °C consistent warming above ambient and heat waves ranging from 0 to 6 °C), eutrophication, herbicide and their interactions on stoichiometric traits of organisms at different trophic levels, which was quantified by stable nitrogen isotopes. Results showed that herbicide treatment had no significant impacts on all stochiometric traits, while warming and eutrophication significantly affected the stoichiometric traits of organisms at lower trophic levels. Eutrophication increased nutrient contents and decreased C: nutrient ratios in primary producers, while the response of N:P ratios depended on the taxonomic group. The contribution of temperature treatments to stoichiometric variation was less than that of eutrophication. Heat waves counteracted the impacts of eutrophication, which was different from the effects of continuous warming, indicating that eutrophication impacts on organism stoichiometric traits depended on climate scenarios. Compared to environmental drivers, taxonomic group was the dominant driver that determined the variations of stoichiometric traits. Furthermore, the stoichiometric stability of organisms was strongly positively correlated with their trophic levels. Our results demonstrate that warming and eutrophication might substantially alter the stoichiometric traits of lower trophic levels, thus impairing the nutrient transfer to higher trophic level, which might further change the structure of food webs and functions of the ecosystems.

Design and experimental validation of an optimized microalgae-bacteria consortium for the bioremediation of glyphosate in continuous photobioreactors

Glyphosate will be banned from Europe by the end of 2022, but its widespread use in the last decades and its persistence in the environment require the development of novel remediation processes. In this work, a bacterial consortium was designed de novo with the aim to remove glyphosate from polluted water, supported by the oxygen produced by a microalgal species. To this goal, bioinformatics tools were employed to identify the bacterial strains from contaminated sources (Pseudomonas stutzeri; Comamonas odontotermitis; Sinomonas atrocyanea) able to express enzymes for glyphosate degradation, while the microalga Chlorella protothecoides was chosen for its known performances in wastewater treatment. To follow a bioaugmentation approach, the designed consortium was cultivated in continuous photobioreactors at increasing glyphosate concentrations, from 5 to 50 mg L^-1, to boost its acclimation to the presence of the herbicide and its capacity to remove it from water. C. protothecoides tolerance to glyphosate was verified through batch experiments. Remarkably, steady state conditions were reached and the consortium was able to live as a community in the reactor. The consortium activity was validated in both synthetic and real wastewater, where glyphosate concentration was reduced by about 53% and 79%, respectively, without the detection of aminomethylphosphonic acid formation.

Genetically engineered microorganisms for environmental remediation

In the recent era, the increasing persistence of hazardous contaminants is badly affecting the globe in many ways. Due to high environmental contamination, almost every second species on earth facing the worst issue in their survival. Advances in newer remediation approaches may help enhance bioremediation's quality, while conventional procedures have failed to remove hazardous compounds from the environment. Chemical and physical waste cleanup approaches have been used in current circumstances; however, these methods are costly and harmful to the environment. Thus, there has been a rise in the use of bioremediation due to an increase in environmental contamination, which led to the development of genetically engineered microbes (GEMs). It is safer and more cost-effective to use engineered microorganisms rather than alternative methods. GEMs are created by introducing a stronger protein into bacteria through biotechnology or genetic engineering to enhance the desired trait. Biodegradation of oil spills, halobenzoates naphthalenes, toluenes, trichloroethylene, octanes, xylenes etc. has been accomplished using GEMs such bacteria, fungus, and algae. Biotechnologically induced microorganisms are more powerful than naturally occurring ones and may degrade contaminants faster because they can quickly adapt to new pollutants they encounter or co-metabolize. Genetic engineering is a worthy process that will benefit the environment and ultimately the health of our people.

Ecological risk assessment of glyphosate and its possible effect on bacterial community in surface sediments of a typical shallow Lake, northern China

Glyphosate is a widely used herbicide worldwide and its prevalent presence in aquatic ecosystems poses a threat to living organisms. This study evaluated potential ecological risk of glyphosate to sediment-dwelling organisms and assessed the probable effect of glyphosate on structure and predicated function of sediment-attached bacterial communities from a large shallow lake in northern China based on 16S rRNA high-throughput sequencing. Results suggested that glyphosate showed a medium to high concentration (up to 8.63 mg/kg) and chronic risk to sediment-dwelling organisms (10% samples exhibiting medium to high risk quotient), especially in sites nearby farmland and residential areas in August. Bacterial community identification based on 16S rRNA sequence indicated some species of dominant phylum Proteobacteria and Campilobacterota (e.g., Steroidobacteraceae, Thiobacillus, Gallionellaceae, Sulfurimonadaceae) were stimulated while some species of dominant phylum Actinobacteriota, Acidobacteriota and Firmicutes (e.g., Nocardioidaceae, Microtrichales, Vicinamibacteraceae, Paenisporosarcina) were inhibited by glyphosate accumulation. The stimulating species were related to sulfur-oxidizing, sulfate-, iron-, or nitrate-reducing bacteria; The inhibiting species were related to plant bacterial endophytes, polyphosphate-accumulating organisms (PAOs) and denitrifers. Correspondingly, promoted bacterial metabolic functions of "sulfite respiration", "nitrogen respiration", "aromatic compound degradation" and "nitrification" but suppressed "cellulolysis", "manganese oxidation", "anoxygenic photoautotrophy S oxidizing" and "nitrate denitrification" were predicated on functional annotation of prokaryotic taxa. Although these results could only partly suggest the impacts of glyphosate on the bacterial communities due to the lack of actual results from control experiments, the identified Steroidobacteraceae could be thought as a bioindicator in the future mechanism study for the ecological effect and bioremediation of glyphosate. This work intends to arise the concern about the depletion of biodiversity and bacterial metabolic functions with contribution of glyphosate in part in eutrophic lakes.

Phytoremediation of industrial effluents assisted by plant growth promoting bacteria

Industrialization plays a crucial role in the economic development of a country; however, the effluents produced as a byproduct generally contain toxic substances which are detrimental to living organisms. In this regard, it is essential to treat these toxic effluents before exposing them to the natural environment by selecting the most appropriate method accordingly. Several techniques are used to remediate industrial effluents including physical, chemical, and biological. Although some physical and chemical remediation technologies are of substantially important in remediation of industrial effluents, however, these technologies are either expensive to be applied by developing countries or not suitable for remediation of all kinds of effluents. In contrast, biological remediation is cost effective, nature friendly, and easy to use for almost all kinds of effluents. Among biological remediation strategies, phytoremediation is considered to be the most suitable method for remediation of industrial effluents; however, the phytoremediation process is slow, takes time in application and some effluents even affect plants growth and development. Alternately, plant microbe interactions could be a winning partner to remediate industrial effluents more efficiently. Among the microbes, plant growth promoting bacteria (PGPB) not only improve plant growth but also help in degradation, sequestration, volatilization, solubilization, mobilization, and bioleaching of industrial effluents which subsequently improve the phytoremediation process. The current study discusses the role of PGPB in enhancing the phytoremediation processes of industrial effluents.

Insights into the microbial degradation and resistance mechanisms of glyphosate

Glyphosate, as one of the broad-spectrum herbicides for controlling annual and perennial weeds, is widely distributed in various environments and seriously threatens the safety of human beings and ecology. Glyphosate is currently degraded by abiotic and biotic methods, such as adsorption, photolysis, ozone oxidation, and microbial degradation. Of these, microbial degradation has become the most promising method to treat glyphosate because of its high efficiency and environmental protection. Microorganisms are capable of using glyphosate as a phosphorus, nitrogen, or carbon source and subsequently degrade glyphosate into harmless products by cleaving C-N and C-P bonds, in which enzymes and functional genes related to glyphosate degradation play an indispensable role. There have been many studies on the abiotic and biotic treatment technologies, microbial degradation pathways and intermediate products of glyphosate, but the related enzymes and functional genes involved in the glyphosate degradation pathways have not been further discussed. There is little information on the resistance mechanisms of bacteria and fungi to glyphosate, and previous investigations of resistance mechanisms have mainly focused on how bacteria resist glyphosate damage. Therefore, this review explores the microorganisms, enzymes and functional genes related to the microbial degradation of glyphosate and discusses the pathways of microbial degradation and the resistance mechanisms of microorganisms to glyphosate. This review is expected to provide reference for the application and improvement of the microbial degradation of glyphosate in microbial remediation.

Surface Plasmon Resonance Imaging Sensor for Detection of Photolytically and Photocatalytically Degraded Glyphosate

Glyphosate is one of the most widely used pesticides, which, together with its primary metabolite aminomethylphosphonic acid, remains present in the environment. Many technologies have been developed to reduce glyphosate amounts in water. Among them, heterogeneous photocatalysis with titanium dioxide as a commonly used photocatalyst achieves high removal efficiency. Nevertheless, glyphosate is often converted to organic intermediates during its degradation. The detection of degraded glyphosate and emerging products is, therefore, an important element of research in terms of disposal methods. Attention is being paid to new sensors enabling the fast detection of glyphosate and its degradation products, which would allow the monitoring of its removal process in real time. The surface plasmon resonance imaging (SPRi) method is a promising technique for sensing emerging pollutants in water. The aim of this work was to design, create, and test an SPRi biosensor suitable for the detection of glyphosate during photolytic and photocatalytic experiments focused on its degradation. Cytochrome P450 and TiO₂ were selected as the detection molecules. We developed a sensor for the detection of the target molecules with a low molecular weight for monitoring the process of glyphosate degradation, which could be applied in a flow-through arrangement and thus detect changes taking place in real-time. We believe that SPRi sensing could be widely used in the study of xenobiotic removal from surface water or wastewater.

Effects of Free or Immobilized Bacterium Stenotrophomonas acidaminiphila Y4B on Glyphosate Degradation Performance and Indigenous Microbial Community Structure

The overuse of glyphosate has resulted in serious environmental contamination. Thus, effective techniques to remove glyphosate from the environment are required. Herein, we isolated a novel strain Stenotrophomonas acidaminiphila Y4B, which completely degraded glyphosate and its major metabolite aminomethylphosphonic acid (AMPA). Y4B degraded glyphosate over a broad concentration range (50-800 mg L^-1), with a degradation efficiency of over 98% within 72 h (50 mg L^-1). Y4B degraded glyphosate via the AMPA pathway by cleaving the C-N bond, followed by degradation of AMPA and subsequent metabolism. Y4B demonstrated strong competitiveness and substantially accelerated the degradation of glyphosate in different soils, degrading 71.93 and 89.81% of glyphosate (400 mg kg^-1) within 5 days in sterile and nonsterile soils, respectively. The immobilized cells of Y4B were more efficient than their free cells and they displayed excellent biodegradation efficiency in a sediment-water system. Taken together, Y4B is an ideal degrader for the bioremediation of glyphosate-contaminated sites.

Influence of glyphosate and its metabolite aminomethylphosphonic acid on aquatic plants in different ecological niches

Glyphosate and its metabolite aminomethylphosphonic acid (AMPA) draw great concern due to their potential threat to aquatic ecosystems. The individual and combined effects of glyphosate and AMPA on aquatic plants in different ecological niches need to be explored. This study aimed to investigate the ecotoxicity of glyphosate and AMPA on the emergent macrophyte Acorus calamus, phytoplankton Chlorella vulgaris, and submerged macrophyte Vallisneria natans after their exposure to glyphosate and AMPA alone and to their mixture. Medium and low concentrations of glyphosate (≤ 0.5 mg L^-1) significantly inhibited the growth of V. natans and promoted the growth of C. vulgaris (P < 0.05) but had no significant effect on the growth of A. calamus (P > 0.05). AMPA (≤ 5.0 mg L^-1) did not significantly influence the relative growth rate (except C. vulgaris) or malonaldehyde levels but significantly altered the expression levels of chlorophyll-related genes and superoxide dismutase [Cu-Zn] genes in the aquatic plants examined. AMPA mainly affected the oxidative phosphorylation pathway in V. natans and not those in other two plants, indicating that V. natans was more sensitive to AMPA-induced oxidative damage. Moreover, antagonistic effects on plant growth were observed when plants were exposed to low concentrations of glyphosate + AMPA (≤ 0.1 + 0.1 mg L^-1). When the concentration of glyphosate + AMPA reached 0.5 + 0.5 and 5.0 + 5.0 mg L^-1, the growth of the submerged macrophyte was additively or synergistically inhibited, but the growth of the emergent macrophyte and phytoplankton was antagonistically inhibited. Our results indicated that both the individual and combined effects of glyphosate and AMPA might alter the vertical structure of shallow lakes and accelerate the conversion of shallow lakes from grass-based to algal-based lakes.

Microcosm test for pesticide fate assessment in planted water filters: 13C,15N-labeled glyphosate as an example

Planted filters are often used to remove pesticides from runoff water. However, the detailed fate of pesticides in the planted filters still remains elusive. This hampers an accurate assessment of environmental risks of the pesticides related to their fate and thereby development of proper mitigation strategies. In addition, a test system for the chemical fate analysis including plants and in particular for planted filters is not well established yet. Therefore, we developed a microcosm test to simulate the fate of pesticide in planted filters, and applied 2-¹³C,¹⁵N-glyphosate as a model pesticide. The fate of 2-¹³C,¹⁵N-glyphosate in the planted microcosms over 31 day-incubation period was balanced and compared with that in the unplanted microcosms. The mass balance of 2-¹³C,¹⁵N-glyphosate turnover included ¹³C mineralization, degradation products, and the ¹³C and ¹⁵N incorporation into the rhizosphere microbial biomass and plants. We observed high removal of glyphosate (> 88%) from the water mainly due to adsorption on gravel in both microcosms. More glyphosate was degraded in the planted microcosms with 4.1% of ¹³C being mineralized, 1.5% of ¹³C and 3.8% of ¹⁵N being incorporated into microbial biomass. In the unplanted microcosms, 1.1% of ¹³C from 2-¹³C,¹⁵N-glyphosate was mineralized, and only 0.2% of ¹³C and 0.1% of ¹⁵N were assimilated into microbial biomass. The total recovery of ¹³C and ¹⁵N was 81% and 85% in planted microcosms, and 91% and 93% in unplanted counterparts, respectively. The microcosm test was thus proven to be feasible for mass balance assessments of the fate of non-volatile chemicals in planted filters. The results of such studies could help better manage and design planted filters for pesticide removal.

Glyphosate and glyphosate-based herbicides (GBHs) induce phenotypic imipenem resistance in Pseudomonas aeruginosa

GBHs are the most widely used herbicides for weed control worldwide that potentially affect microorganisms, but the role of their sublethal exposure in the development of antibiotic resistance of Pseudomonas aeruginosa is still not fully investigated. Here, the effects of glyphosate acid (GLY), five glyphosate-based herbicides (GBHs), and POE(15), a formerly used co-formulant, on susceptibility to imipenem, a potent carbapenem-type antibiotic, in one clinical and four non-clinical environmental P. aeruginosa isolates were studied. Both pre-exposure in broth culture and co-exposure in solid media of the examined P. aeruginosa strains with 0.5% GBHs resulted in a decreased susceptibility to imipenem, while other carbapenems (doripenem and meropenem) retained their effectiveness. Additionally, the microdilution chequerboard method was used to examine additive/antagonistic/synergistic effects between GLY/POE(15)/GBHs and imipenem by determining the fractional inhibitory concentration (FIC) indexes. Based on the FIC index values, glyphosate acid and Total demonstrated a potent antagonistic effect in all P. aeruginosa strains. Dominator Extra 608 SL and Fozat 480 reduced the activity of imipenem in only one strain (ATCC10145), while POE(15) and three other GBHs did not have any effect on susceptibility to imipenem. Considering the simultaneous presence of GBHs and imipenem in various environmental niches, the detected interactions between these chemicals may affect microbial communities. The mechanisms of the glyphosate and GBH-induced imipenem resistance in P. aeruginosa are yet to be investigated.

Heat waves rather than continuous warming exacerbate impacts of nutrient loading and herbicides on aquatic ecosystems

Submerged macrophytes are vital components in shallow aquatic ecosystems, but their abundances have declined globally. Shading by periphyton and phytoplankton/turbidity plays a major role in this decline, and the competing aquatic primary producers are subject to the complex influence of multiple stressors such as increasing temperatures, nutrient loading and herbicides. Their joint impact has rarely been tested and is difficult to predict due to potentially opposing effects on the different primary producers, their interactions and their grazers. Here, we used 48 mesocosms (2500 L) to simulate shallow lakes dominated by two typical submerged macrophytes, bottom-dwelling Vallisneria denseserrulata and canopy-forming Hydrilla verticillata, and associated food web components. We applied a combination of nutrient loading, continuous warming, heat waves and glyphosate-based herbicides to test how these stressors interactively impact the growth of submerged macrophytes, phytoplankton and periphyton as competing primary producers. Warming or heat waves alone did not affect phytoplankton and periphyton abundance, but negatively influenced the biomass of V. denseserrulata. Nutrient loading alone increased phytoplankton biomass and water turbidity and thus negatively affected submerged macrophyte biomass, particularly for V. denseserrulata, by shading. Glyphosate alone did not affect biomass of each primary producer under ambient temperatures. However, heat waves facilitated phytoplankton growth under combined nutrient loading and glyphosate treatments more than continuous warming. As a consequence, H. verticillata biomass was lowest under these conditions indicating the potential of multiple stressors for macrophyte decline. Our study demonstrated that multiple stressors interactively alter the biomass of primary producers and their interactions and can eventually lead to a loss of macrophyte communities and shift to phytoplankton dominance. These results show the risks in shallow lakes and ponds in agricultural landscapes and underline the need for multiple stressor studies as a base for their future management.

Herbicide Roundup shows toxic effects in nontarget organism Drosophila

Glyphosate-based herbicide Roundup, as the most employed herbicide used for multiple purposes in agriculture, adversely affects nontarget organisms. We tested the effects of Roundup applied at larval and adult stages. Roundup caused developmental delay and increased larvae mortality. Roundup treatment reduced hemolymph glucose and glycogen levels in adult flies of both sexes at the highest concentration tested. Sex-dependent diverse effects were found in catalase and Cu,Zn superoxide dismutase (Cu,Zn-SOD) activities. Decreased aconitase activity, contents of thiols, and lipid peroxides were found after larval Roundup exposure. Furthermore, chronic exposure to adult flies decreased appetite, body weight, and shortened lifespan. Thus, our results suggest that high concentrations of Roundup are deleterious to both larvae and adults, resulting in a shift of the metabolism and antioxidant defense system in Drosophila melanogaster.

Chronic Toxicity of Primary Metabolites of Chloroacetamide and Glyphosate to Early Life Stages of Marbled Crayfish Procambarus virginalis

Degradation products of herbicides, alone and in combination, may affect non-target aquatic organisms via leaching or runoff from the soil. The effects of 50-day exposure of primary metabolites of chloroacetamide herbicide, acetochlor ESA (AE; 4 µg/L), and glyphosate, aminomethylphosphonic acid (AMPA; 4 µg/L), and their combination (AMPA + AE; 4 + 4 µg/L) on mortality, growth, oxidative stress, antioxidant response, behaviour, and gill histology of early life stages of marbled crayfish (Procambarus virginalis) were investigated. While no treatment effects were observed on cumulative mortality or early ontogeny, growth was significantly lower in all exposed groups compared with the control group. Significant superoxide dismutase activity was observed in exposure groups, and significantly higher glutathione S-transferase activity only in the AMPA + AE group. The gill epithelium in AMPA + AE-exposed crayfish showed swelling as well as numerous unidentified fragments in interlamellar space. Velocity and distance moved in crayfish exposed to metabolites did not differ from controls, but increased activity was observed in the AMPA and AE groups. The study reveals the potential risks of glyphosate and acetochlor herbicide usage through their primary metabolites in the early life stages of marbled crayfish.

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.