Insights into the microbial degradation and resistance mechanisms of glyphosate

Pseudomonas putida HE alleviates glyphosate-induced toxicity in earthworm: Insights from the neurological, reproductive and immunological status

The proceeding study aimed to isolate glyphosate-degrading bacteria from soil and determine optimal degradation conditions through single-factor experiments and response surface methodology. The detoxifying efficacy of the isolate on glyphosate was assessed using earthworm model. The results indicate that Pseudomonas putida HE exhibited the highest glyphosate degradation rate. Optimal conditions for glyphosate degradation were observed at an inoculation percentage of approximately 5%, a pH of 7, and a temperature of 30 °C. Glyphosate induced notable neurotoxicity and reproductive toxicity in earthworms, evidenced by reduced activity of the neurotoxicity-associated enzyme AChE. Additionally, an increase in the activities of catalase, superoxide dismutase, and lactate dehydrogenase was observed. H&E staining revealed structural disruptions in the earthworm clitellum, with notable atrophy in the structure of spermathecae. Furthermore, glyphosate activation of earthworm immune systems led to increased expression of immune-related genes, specifically coelomic cytolytic factor and lysozyme. Notably, the introduction of strain HE mitigated the glyphosate toxicity to the earthworms mentioned above. P. putida HE was able to increase soil enzyme activities that were reduced due to glyphosate. The isolate P. putida HE, emerged as an effective and cost-efficient remedy for glyphosate degradation and toxicity reduction in natural settings, showcasing potential applications in real ecological settings.

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.

Nitrogen-fertilizer addition to an agricultural soil enhances biogenic non-extractable residue formation from 2-13C,15N-glyphosate

Glyphosate and nitrogen (N) or (P) phosphorus fertilizers are often applied in combination to agricultural fields. The additional P or N supply to microorganisms might drive glyphosate degradation towards sarcosine/glycine or aminomethylphosphonic acid (AMPA), and consequently determine the speciation of non-extractable residues (NERs): harmless biogenic NERs (bioNERs) or potentially hazardous xenobiotic NERs (xenoNERs). We therefore investigated the effect of P or N-fertilizers on microbial degradation of glyphosate and bioNER formation in an agricultural soil. Four different treatments were incubated at 20 °C for 75 days as follows; I: no fertilizer (2-13C,15N-glyphosate only, control), II: P-fertilizer (superphosphate + 2-13C,15N-glyphosate, effect of P-supply), III: N-fertilizer (ammonium nitrate + 2-13C,15N-glyphosate, effect of N-supply) and IV: 15N-fertilizer (15N-ammonium nitrate + 2-13C-glyphosate, differentiation between microbial assimilations of 15N: 15N-fertilizer versus 15N-glyphosate). We quantified 13C or 15N in mineralization, extractable residues, NERs and in amino acids (AAs). At the end, mineralization (36-41 % of the 13C), extractable 2-13C,15N-glyphosate/2-13C-glyphosate (0.42-0.49 %) & 15N-AMPA (1.2 %), and 13C/15N-NERs (40-43 % of the 13C, 40-50 % of the 15N) were comparable among treatments. Contrastingly, the 15N-NERs from 15N-fertlizer amounted to only 6.6 % of the 15N. Notably, N-fertilizer promoted an incorporation of 13C/15N from 2-13C,15N-glyphosate into AAs and thus the formation of 13C/15N-bioNERs. The 13C/15N-AAs were as follows: 16-21 % (N-fertilizer) > 11-13 % (control) > 7.2-7.3 % (P-fertilizer) of the initially added isotope. 2-13C,15N-glyphosate was degraded via the sarcosine/glycine and AMPA simultaneously in all treatments, regardless of the treatment type. The percentage share of bioNERs within the NERs in the N-fertilized soil was highest (13C: 80-82 %, 15N: 100 %) compared to 53 % (13C & 15N, control) and to only 30 % (13C & 15N, P-fertilizer). We thus concluded simultaneous N & glyphosate addition to soils could be beneficial for the environment due to the enhanced bioNER formation, while P & glyphosate application disadvantageous since it promoted xenoNER formation.

Both acute glyphosate and the aminomethylphosphonic acid intoxication decreased the acetylcholinesterase activity in rat hippocampus, prefrontal cortex and gastrocnemius muscle

It has been reported that glyphosate, one of the most common herbicides used in agriculture, impairs locomotion and cognition. Glyphosate has a variable half-life in soil up to biotic and/or abiotic factors transform the molecule in metabolites such as the aminomethylphosphonic acid (AMPA) that has a longer half-life. In this study, female Sprague Dawley rats were acutely exposed to different doses of glyphosate or AMPA (i.e. 10, 56 or 100 mg/kg) and, subsequently, the acetylcholinesterase (AChE) activity was measured in the hippocampus, prefrontal cortex (PFC) and the gastrocnemius muscle. Both glyphosate and AMPA produced a similar decrease in the AChE activity in all the tissues tested. These results suggest that interference with normal cholinergic neurotransmission may be one of the mechanisms involved in glyphosate-induced motor alterations in rats. Moreover, our results highlight the biological importance of AMPA as a molecule with anticholinesterase action in brain and skeletal muscle. To our knowledge, this is the first report showing in vivo that AMPA, the major metabolite of glyphosate, behaves as an organophosphate.

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.

Yeast of Eden: microbial resistance to glyphosate from a yeast perspective

First marketed as RoundUp, glyphosate is history's most popular herbicide because of its low acute toxicity to metazoans and broad-spectrum effectiveness across plant species. The development of glyphosate-resistant crops has led to increased glyphosate use and consequences from the use of glyphosate-based herbicides (GBH). Glyphosate has entered the food supply, spurred glyphosate-resistant weeds, and exposed non-target organisms to glyphosate. Glyphosate targets EPSPS/AroA/Aro1 (orthologs across plants, bacteria, and fungi), the rate-limiting step in the production of aromatic amino acids from the shikimate pathway. Metazoans lacking this pathway are spared from acute toxicity and acquire their aromatic amino acids from their diet. However, glyphosate resistance is increasing in non-target organisms. Mutations and natural genetic variation discovered in Saccharomyces cerevisiae illustrate similar types of glyphosate resistance mechanisms in fungi, plants, and bacteria, in addition to known resistance mechanisms such as mutations in Aro1 that block glyphosate binding (target-site resistance (TSR)) and mutations in efflux drug transporters non-target-site resistance (NTSR). Recently, genetic variation and mutations in an amino transporter affecting glyphosate resistance have uncovered potential off-target effects of glyphosate in fungi and bacteria. While glyphosate is a glycine analog, it is transported into cells using an aspartic/glutamic acid (D/E) transporter. The size, shape, and charge distribution of glyphosate closely resembles D/E, and, therefore, glyphosate is a D/E amino acid mimic. The mitochondria use D/E in several pathways and mRNA-encoding mitochondrial proteins are differentially expressed during glyphosate exposure. Mutants downstream of Aro1 are not only sensitive to glyphosate but also a broad range of other chemicals that cannot be rescued by exogenous supplementation of aromatic amino acids. Glyphosate also decreases the pH when unbuffered and many studies do not consider the differences in pH that affect toxicity and resistance mechanisms.

Slow release of attapulgite based nano-enabled glyphosate improves soil phosphatase activity, organic P-pool and proliferation of dominant bacterial community

Glyphosate (Glp) was encapsulated onto the dopamine-modified attapulgite to develop an attapulgite-based nano-enabled Glp (DGlp) in this study with comparable weed control effects to pure Glp and commercial Glp solutions. Within 24 hours, the active Glp molecule was slowly released from DGlp at a maximum remaining rate of over 90%, and then degraded similarly to Glp solution in soil. The addition of DGlp improved soil available phosphorus (P) contents, phosphatase activity, and enzyme extractable P fraction. However, compared to Glp solution, DGlp addition had no effect on the transformation of soil inorganic P fractions. The 16S rRNA sequencing and co-occurrence network results revealed that DGlp had no significant effect on the soil bacterial diversity but diminished the complexity of soil bacterial network. According to the Mantel test, DGlp addition stimulated soil phosphatase activity and proliferation of dominant bacterial taxa (Proteobacteria and Firmicutes) capable of degrading Glp. Proteobacteria and Firmicutes that had been extensively recruited and enriched for their phosphatase activities may have mobilized reactive enzyme-P, significantly enhancing the transformation of reactive organic P and P-pool in soil. These results contributed to our understanding of the ecotoxicity and environmental impacts of nano-enabled Glp prior to its successful and sustainable application in agriculture.

New roles for Bacillus thuringiensis in the removal of environmental pollutants

For a long time, the well-known Gram-positive bacterium Bacillus thuringiensis (Bt) has been extensively studied and developed as a biological insecticide for Lepidoptera and Coleoptera pests due to its ability to secrete a large number of specific insecticidal proteins. In recent years, studies have found that Bt strains can also potentially biodegrade residual pollutants in the environment. Many researchers have isolated Bt strains from multiple sites polluted by exogenous compounds and characterized and identified their xenobiotic-degrading potential. Furthermore, its pathway for degradation was also investigated at molecular level, and a number of major genes/enzymes responsible for degradation have been explored. At present, a variety of xenobiotics involved in degradation in Bt have been reported, including inorganic pollutants (used in the field of heavy metal biosorption and recovery and precious metal recovery and regeneration), pesticides (chlorpyrifos, cypermethrin, 2,2-dichloropropionic acid, etc.), organic tin, petroleum and polycyclic aromatic hydrocarbons, reactive dyes (congo red, methyl orange, methyl blue, etc.), and ibuprofen, among others. In this paper, the biodegrading ability of Bt is reviewed according to the categories of related pollutants, so as to emphasize that Bt is a powerful agent for removing environmental pollutants.

Microbial degradation as a powerful weapon in the removal of sulfonylurea herbicides

Sulfonylurea herbicides have been widely used worldwide and play a significant role in modern agricultural production. However, these herbicides have adverse biological effects that can damage the ecosystems and harm human health. As such, rapid and effective techniques that remove sulfonylurea residues from the environment are urgently required. Attempts have been made to remove sulfonylurea residues from environment using various techniques such as incineration, adsorption, photolysis, ozonation, and microbial degradation. Among them, biodegradation is regarded as a practical and environmentally responsible way to eliminate pesticide residues. Microbial strains such as Talaromyces flavus LZM1, Methylopila sp. SD-1, Ochrobactrum sp. ZWS16, Staphylococcus cohnii ZWS13, Enterobacter ludwigii sp. CE-1, Phlebia sp. 606, and Bacillus subtilis LXL-7 can almost completely degrade sulfonylureas. The degradation mechanism of the strains is such that sulfonylureas can be catalyzed by bridge hydrolysis to produce sulfonamides and heterocyclic compounds, which deactivate sulfonylureas. The molecular mechanisms associated with microbial degradation of sulfonylureas are relatively poorly studied, with hydrolase, oxidase, dehydrogenase and esterase currently known to play a pivotal role in the catabolic pathways of sulfonylureas. Till date, there are no reports specifically on the microbial degrading species and biochemical mechanisms of sulfonylureas. Hence, in this article, the degradation strains, metabolic pathways, and biochemical mechanisms of sulfonylurea biodegradation, along with its toxic effects on aquatic and terrestrial animals, are discussed in depth in order to provide new ideas for remediation of soil and sediments polluted by sulfonylurea herbicides.

Glyphosate and environmental toxicity with "One Health" approach, a review

The herbicide Glyphosate (GLY), or N-(phosphonomethyl) glycine was synthesized in 1950 and applied to control weeds in agricultural production. For a long time, it was believed that it was an inert compound, but many studies have instead demonstrated over the years the dangers of GLY to the ecosystem and human health. Among the best-known effects, it is known that GLY interferes with the metabolic pathways of plants and the main groups of microorganisms, negatively influencing their growth. GLY interferes with the metabolic pathways of plants and major groups of microorganisms negatively affecting their growth. The extensive GLY application on fields results in a "slow death" of plants through the minor resistance to root pathogens and in increasing pollution of freshwaters and soils. Unfortunately, however, unlike the old beliefs, GLY can reach non-target destinations, in this regard, ecological studies and environmental epidemiology are of significant interest. In this review, we focus on the effects of acute and chronic exposure to GLY on the health of plants, animals, and humans from a One Health perspective. GLY has been linked to neurological and endocrine issues in both humans and animals, and behavioral modification on specific bioindicators, but the knowledge about the ratio cause-and-effect still needs to be better understood and elucidated. Environmental GLY residues analysis and policy acts will both require new criteria to protect environmental and human health.

The Microbial Degradation of Natural and Anthropogenic Phosphonates

Phosphonates are compounds containing a direct carbon-phosphorus (C-P) bond, which is particularly resistant to chemical and enzymatic degradation. They are environmentally ubiquitous: some of them are produced by microorganisms and invertebrates, whereas others derive from anthropogenic activities. Because of their chemical stability and potential toxicity, man-made phosphonates pose pollution problems, and many studies have tried to identify biocompatible systems for their elimination. On the other hand, phosphonates are a resource for microorganisms living in environments where the availability of phosphate is limited; thus, bacteria in particular have evolved systems to uptake and catabolize phosphonates. Such systems can be either selective for a narrow subset of compounds or show a broader specificity. The role, distribution, and evolution of microbial genes and enzymes dedicated to phosphonate degradation, as well as their regulation, have been the subjects of substantial studies. At least three enzyme systems have been identified so far, schematically distinguished based on the mechanism by which the C-P bond is ultimately cleaved-i.e., through either a hydrolytic, radical, or oxidative reaction. This review summarizes our current understanding of the molecular systems and pathways that serve to catabolize phosphonates, as well as the regulatory mechanisms that govern their activity.

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.

Glyphosate induces autophagy in hepatic L8824 cell line through NO-mediated activation of RAS/RAF/MEK/ERK signaling pathway and energy metabolism disorders

Glyphosate is an herbicide commonly used worldwide, and its substantial use causes widespread pollution with runoff. However, research on glyphosate toxicity has mostly remained at the embryonic level and existing studies are limited. In the present study, we investigated whether glyphosate can induce autophagy in hepatic L8824 cells by regulating energy metabolism and rat sarcoma (RAS)/rapidly accelerated fibrosarcoma (RAF)/mitogen-activated extracellular signal-regulated kinase (MEK)/extracellular regulated protein kinases (ERK) signaling by activating nitric oxide (NO). First, we selected 0, 50, 200, and 500 μg/mL as the challenge doses, according to the inhibitory concentration of 50% (IC50) of glyphosate. The results showed that glyphosate exposure increased the enzyme activity of inducible nitric oxide synthase (iNOS), which in turn increased the NO content. The activity and expression of enzymes related to energy metabolism, such as hexokinase (HK)1, HK2, phosphofructokinase (PFK), phosphokinase (PK), succinate dehydrogenase (SDH), and nicotinamide adenine dinucleotide with hydrogen (NADH), were inhibited, and the RAS/RAF/MEK/ERK signaling pathway was activated. This led to the negative expression of mammalian target of rapamycin (mTOR) and P62 in hepatic L8824 cells and the activation of the autophagy marker genes microtubule-associated proteins light chain 3 (LC3) and Beclin1 to induce autophagy. The above results were dependent on glyphosate concentration. To verify whether autophagy can be excited by the RAS/RAF/MEK/ERK signaling pathway, we treated L8824 cells with the ERK inhibitor U0126 and found that the autophagy gene LC3 was reduced due to the inhibition of ERK, thus demonstrating the reliability of the results. In conclusion, our results demonstrate that glyphosate can induce autophagy in hepatic L8824 cells by activating NO, thus regulating energy metabolism and the RAS/RAF/MEK/ERK signaling pathway.

Current insights into the microbial degradation of nicosulfuron: Strains, metabolic pathways, and molecular mechanisms

Nicosulfuron is among the sulfonylurea herbicides that are widely used to control annual and perennial grass weeds in cornfields. However, nicosulfuron residues in the environment are likely to cause long-lasting harmful environmental and biological effects. Nicosulfuron degrades via photo-degradation, chemical hydrolysis, and microbial degradation. The latter is crucial for pesticide degradation and has become an essential strategy to remove nicosulfuron residues from the environment. Most previous studies have focused on the screening, degradation characteristics, and degradation pathways of biodegrader microorganisms. The isolated nicosulfuron-degrading strains include Bacillus, Pseudomonas, Klebsiella, Alcaligenes, Rhodopseudomonas, Ochrobactrum, Micrococcus, Serratia, Penicillium, Aspergillus, among others, all of which have good degradation efficiency. Two main intermediates, 2-amino-4,6-dimethoxypyrimidine (ADMP) and 2-aminosulfonyl-N,N-dimethylnicotinamide (ASDM), are produced during microbial degradation and are derived from the C-N, C-S, and S-N bond breaks on the sulfonylurea bridge, covering almost every bacterial degradation pathway. In addition, enzymes related to the degradation of nicosulfuron have been identified successively, including the manganese ABC transporter (hydrolase), Flavin-containing monooxygenase (oxidase), and E3 (esterase). Further in-depth studies based on molecular biology and genetics are needed to elaborate on their role in the evolution of novel catabolic pathways and the microbial degradation of nicosulfuron. To date, few reviews have focused on the microbial degradation and degradation mechanisms of nicosulfuron. This review summarizes recent advances in nicosulfuron degradation and comprehensively discusses the potential of nicosulfuron-degrading microorganisms for bioremediating contaminated environments, providing a reference for further research development on nicosulfuron biodegradation in the future.

Impact of pesticides exposure during neurodevelopmental period on autism spectrum disorders - A focus on gut microbiota

Accumulating evidence indicates exposure to pesticides during the crucial neurodevelopmental period increases susceptibility to many diseases, including the neurodevelopmental disorder known as autism spectrum disorder (ASD). In the last few years, it has been hypothesized that gut microbiota dysbiosis is strongly implicated in the aetiopathogenesis of ASD. Recently, new studies have suggested that the gut microbiota may be involved in the neurological and behavioural defects caused by pesticides, including ASD symptoms. This review highlights the available evidence from recent animal and human studies on the relationship between pesticides that have the potential to disturb intestinal microbiota homeostasis, and ASD symptoms. The mechanisms through which gut microbiota dysbiosis may trigger ASD-like behaviours induced by pesticides exposure during the neurodevelopmental period via the altered production of bacterial metabolites (short chain fatty acids, lipids, retinol, and amino acid) are also described. According to recent research, gut microbiota dysbiosis may be a major contributor to the symptoms of ASD associated with pesticides exposure. However, to determine the detailed mechanism of action of gut microbiota on pesticide-induced ASD behaviours, actual population exposure scenarios from epidemiological studies should be used as the basis for the appropriate exposure pattern and dosage to be used in animal studies.

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.

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.

Ferrihydrite-loaded water hyacinth-derived biochar for efficient removal of glyphosate from aqueous solution

Ferrihydrite-loaded water hyacinth-derived biochar (FH/WHBC) was prepared by in-situ precipitation method to treat glyphosate-containing wastewater. The adsorption properties and mechanism, and actual application potential were deeply studied. Results showed that the adsorption performance of FH/WHBC was closely related with the precipitation pH condition, and the adsorbent prepared at pH 5.0 possessed the highest adsorption capacity of 116.8 mg/g for glyphosate. The isothermal and kinetic experiments showed that the adsorption of glyphosate was consistent with Langmuir model, and the adsorption process was rapid and could be achieved within 30 min. The prepared FH/WHBC was more suitable for application under high acidity environment, and could maintain the great adsorption performances in the presence of most co-existing ions. Besides, it also possessed a good regenerability. Under dynamic condition, the adsorption performance of FH/WHBC was not affected even at high flow rate and high glyphosate concentration. Furthermore, the FH/WHBC can keep excellent removal efficiency for glyphosate in wastewater treatment, and the concentration of glyphosate can be reduced to 0.06 mg·L^-1, which was lower than the groundwater quality of class II mandated in China. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) characterization indicated that the adsorption of glyphosate on FH/WHBC was mainly accomplished through electrostatic adsorption and the formation of inner-sphere complexes. In brief, the prepared sorbent FH/WHBC was expected to be used in the treatment of industrial glyphosate wastewater.

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.

Bioremediation potential of laccase for catalysis of glyphosate, isoproturon, lignin, and parathion: Molecular docking, dynamics, and simulation

The present study aimed to investigate the catalytic degradation produced by laccase in the detoxification of glyphosate, isoproturon, lignin polymer, and parathion. We explored laccase-glyphosate, laccase-lignin polymer, laccase-isoproturon, and laccase-parathion using molecular docking (MD) and molecular dynamics simulation (MDS) approaches. The results suggest that laccase interacts well with glyphosate, lignin polymer, isoproturon, and parathion during biodegradation. We calculated the root mean square deviations (RMSD) of laccase-glyphosate, laccase-lignin polymer, laccase-isoproturon, and laccase-parathion as 0.24 ± 0.02, 0.59 ± 0.32, 0.43 ± 0.07, and 0.43 ± 0.06 nm, respectively. In an aqueous solution, the stability of laccase with glyphosate, lignin polymer, isoproturon, and parathion is mediated through the formation of hydrophobic interactions, hydrogen bonds, and van der Waals interactions. The presence of xenobiotic toxic compounds in the active site changed the conformation of laccase. MDS of the laccase-substrate complexes confirmed their stability during catalytic degradation. Laccase assay results confirmed that the degradation of syringol, dihydroconiferyl alcohol, guaiacol, parathion, isoproturon, and glyphosate were 100%, 99.31%, 95.69%, 60.96%, 54.51%, and 48.34% within 2 h, respectively. Taken together, we describe a novel method to understand the molecular-level biodegradation of xenobiotic compounds through laccase and its potential application in contaminant removal.

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.