Novel pathway of cypermethrin biodegradation in a Bacillus sp. strain SG2 isolated from cypermethrin-contaminated agriculture field

Degradation Kinetics and Mechanism of β-Cypermethrin and 3-Phenoxybenzoic Acid by Lysinibacillus pakistanensis VF-2 in Soil Remediation

Pyrethroid pesticide residues have detrimental effects on soil ecology and crop growth during insecticidal operations in agriculture. In this study, a novel strain Lysinibacillus pakistanensis VF-2 was isolated from long-term pesticide-treated cropland and had a maximum degradation efficiency of 81.66% for synthetic pyrethroid β-cypermethrin (β-CY) under optimized conditions. The analysis of intermediate products revealed that the degradation pathway of β-CY mainly involves ester bond hydrolysis, diphenyl ether decomposition, and phthalate ester degradation. Whole-genome sequencing and RT-qPCR analysis revealed the involvement of carboxylesterases, dioxygenases, and aromatic compound degrading enzymes in the degradation of β-CY. In the soil bioaugmentation experiment, the strain VF-2 can synergistically interact with indigenous microorganisms, significantly enhancing the degradation efficiency of β-CY and its metabolite 3-phenoxybenzoic acid (3-PBA) from 17.08% and 7.62% to 73.46% and 62.29%, respectively. This study suggests that strain VF-2 is a promising candidate for in situ coremediation of pyrethroid and intermediate metabolite residues in soil.

Co-metabolic degradation and metabolite detection of hexabromocyclododecane by Shewanella oneidensis MR-1

Hexabromocyclododecane (HBCD) is a widely used brominated flame retardant; however, it is a persistent organic pollutant as well as affects the human thyroid hormones and causes cancer. However, the degradation of HBCD has received little attention from researchers. Due to its bioaccumulative and hazardous properties, an appropriate strategy for its remediation is required. In this study, we investigated the biodegradation of HBCD using Shewanella oneidensis MR-1 under optimized conditions. The Box-Behnken design (BBD) was implemented for the optimization of the physical degradation parameters of HBCD. S. oneidensis MR-1 showed the best degradation performance at a temperature of 30 °C, pH 7, and agitation speed of 115 rpm, with an HBCD concentration of 1125 μg/L in mineral salt medium (MSM). The strain tolerated up to 2000 μg/L HBCD. Gas chromatography-mass spectrometry analysis identified three intermediates, including 2-bromo dodecane, 2,7,10-trimethyldodecane, and 4-methyl-1-decene. The results provide an insightful understanding of the biodegradation of HBCD by S. oneidensis MR-1 under optimized conditions and could pave the way for further eco-friendly applications. KEY POINTS: • HBCD biodegradation by Shewanella oneidensis • Optimization of HBCD biodegradation by the Box-Behnken analysis • Identification of useful metabolites from HBCD degradation.

Interaction and effects of temperature preference under a controlled environment on the diversity and abundance of the microbiome in Lutzomyia longipalpis (Diptera: Psychodidae)

Characterization of the temperature effects on the abundance and richness of the microbiota of Lutzomyia longipalpis, insect vector of Leishmania infantum in America, is an aspect of pivotal importance to understand the interactions between temperature, bacteria, and Leishmania infection. We developed and used a customized device with a temperature gradient (21-34 °C) to assess the temperature preferences of wild females of Lu. longipalpis collected in a rural area (Ricaurte, Cundinamarca, Colombia). Each replicate consisted of 50 females exposed to the gradient for an hour. At the end of the exposure time, insects were collected and separated by the temperature ranges selected varying from 21 °C to 34 °C. They were organized in 17 pools from which total DNA extracts were obtained, and samples were subjected to 16S rRNA amplicon sequencing analyzes. The most abundant phyla across the different temperature ranges were Proteobacteria (17.22-90.73 %), Firmicutes (5.99-77.21 %) and Actinobacteria (1.56-59.85 %). Results also showed an abundance (30 % to 57.36 %) of Pseudomonas (mainly at temperatures of 21-29 °C and 34 °C) that decreased to 6.55 %-13.20 % at temperatures of 31-33 °C, while Bacillus increase its abundance to 67.24 % at 29-33 °C. Serratia also had a greater representation (49.79 %), specifically in sand flies recovered at 25-27 °C. No significant differences were found at α-diversity level when comparing richness using the Shannon-Wiener, Simpson, and Chao1 indices, while β-diversity differences were found using the Bray-Curtis index (F-value of 3.5073, p-value < 0.013, R-squared of 0,4889), especially in the groups of Lu. longipalpis associated at higher temperatures (29-33 °C). It was also possible to detect the presence of endosymbionts such as Spiroplasma and Arsenophonus in the range of 29-33 °C. Rickettsia was only detected in Lu. longipalpis sand flies recovered between 25-27 °C. It was possible to characterize Lu. longipalpis microbiota in response to intraspecific temperature preferences and observe changes in bacterial communities and endosymbionts at different ranges of said environmental variable, which may be important in its vector competence and environmental plasticity to adapt to new climate change scenarios.

Biodegradation of monocrotophos, cypermethrin & fipronil by Proteus myxofaciens VITVJ1: A plant - microbe based remediation

Current study was focused on the degradation of pesticides such as Monocrotophos, Cypermethrin & Fipronil (M, C & F) using phyto and rhizoremediation strategies. The isolate Proteus myxofaciens (VITVJ1) obtained from agricultural soil was capable of degrading M, C & F. The bacteria exhibited resistance to all the pesticides (M, C & F) up to 1500 ppm and was also capable of forming biofilms. The degraded products identified using Gas Chromatography-Mass Spectroscopy (GC-MS) and FTIR was further used for deriving the degradation pathway. The end product of M, C & F was acetic acid and 3-phenoxy benzoic acid which was confirmed by the presence of functional groups such as C=O and OH. Seed germination assay revealed the non-toxic nature of the degraded products with increased germination index in the treatments augmented with degraded products. The candidate genes such as opdA gene, Est gene and MnP1gene was amplified with the amplicon size of 700bp, 1200bp and 500bp respectively. P. myxofaciens not only degraded M, C & F, but was also found to be a plant growth promoting rhizobacteria. Since, it was capable of producing Indole Acetic acid (IAA), siderophore and was able to solubilize insoluble phosphate. Therefore, VITVJ1 upon augmentation to the rhizoremediation setup aided the degradation of pesticides with increase in plant growth as compared to that of the phytoremediation setup. To our knowledge this is the first study where P. myxofaciens has been effectively used for the degradation of three different classes of pesticides, which could also enhance the growth of plants and simultaneously degrade M, C & F.

Impact of carbendazim on cellular growth, defence system and plant growth promoting traits of Priestia megaterium ANCB-12 isolated from sugarcane rhizosphere

Agrochemicals are consistently used in agricultural practices to protect plants from pathogens and ensure high crop production. However, their overconsumption and irregular use cause adverse impacts on soil flora and non-target beneficial microorganisms, ultimately causing a hazard to the ecosystem. Taking this into account, the present study was conducted to determine the high dosage of fungicide (carbendazim: CBZM) effects on the rhizobacteria survival, plant growth promoting trait and reactive oxygen species (ROS) scavenging antioxidant enzyme system. Thus, a multifarious plant growth promoting rhizobacteria (PGPR) isolate, ANCB-12, was obtained from the sugarcane rhizosphere through an enrichment technique. The taxonomic position of the isolated rhizobacteria was confirmed through 16S rRNA gene sequencing analysis as Priestia megaterium ANCB-12 (accession no. ON878101). Results showed that increasing concentrations of fungicide showed adverse effects on rhizobacterial cell growth and survival. In addition, cell visualization under a confocal laser scanning microscope (CLSM) revealed more oxidative stress damage in the form of ROS generation and cell membrane permeability. Furthermore, the increasing dose of CBZM gradually decreased the plant growth promoting activities of the rhizobacteria ANCB-12. For example, CBZM at a maximum 3,000 μg/ml concentration decreases the indole acetic acid (IAA) production by 91.6%, ACC deaminase by 92.3%, and siderophore production by 94.1%, respectively. Similarly, higher dose of fungicide enhanced the ROS toxicity by significantly (p < 0.05) modulating the stress-related antioxidant enzymatic biomarkers in P. megaterium ANCB-12. At a maximum 3,000 μg/ml CBZM concentration, the activity of superoxide dismutase (SOD) declined by 82.3%, catalase (CAT) by 61.4%, glutathione peroxidase (GPX) by 76.1%, and glutathione reductase (GR) by 84.8%, respectively. The results of this study showed that higher doses of the fungicide carbendazim are toxic to the cells of plant-beneficial rhizobacteria. This suggests that a recommended dose of fungicide should be made to lessen its harmful effects.

Process optimization of cypermethrin biodegradation by regression analysis and parametric modeling along with biochemical degradation pathway

Pyrethroid pesticides are of great environmental and health concern with regard to neurotoxicity and ubiquitous occurrence. Here, we reported a new bacterial strain identified as Bacillus cereus AKAD 3-1 that degraded 88.1% of 50 mg/l of cypermethrin in an aqueous medium. The biodegradation of cypermethrin was optimized by CCD (central composite design) and validated by ANN-GA (artificial neural network-genetic algorithm). Both the approaches proved to possess good performance in modeling and optimizing the growth conditions. Results indicated that the process variables have a significant (< 0.0001) impact on cypermethrin biodegradation. Moreover, the predicted CCD model had a "lack of fit p-value" of "0.9975." The optimum CCD and ANN model had an R² value of 0.9703 and 0.9907, indicating that the two models' experimental and predicted values are closely fitted. The isolate successfully converted cypermethrin to CO₂ and phenol without producing any toxic metabolite. Finally, a degradation pathway was proposed with the intermediate compounds identified by GC-MS. The present study highlights an important potential application of strain AKAD 3-1 for the in situ bioremediation of cypermethrin-contaminated environments.

Whole-genome analysis guided molecular mechanism of cyanogenic glucoside degradation by yeast isolated from Prunus mume fruit syrup

Consumption of fermented Prunus mume fruit (maesil) sugar syrup raise a health concern due to the presence of the cyanogenic glucoside amygdalin. The goal of the present study was to investigate the amygdalin degradation potential and genome profile of the native microbes found in maesil syrup. The microbial profile analysis revealed that yeast is the predominant microorganism native to maesil syrup and that the isolated yeast cells showed a remarkable potential for amygdalin reduction (99.7%). Moreover, the reduction in amygdalin was inversely proportional to the growth of the isolated yeast. The whole-genome analysis revealed that the isolated yeast is Zygosaccharomyces rouxii (genome size 10 Mb, 39.25% of GC content). Of the 5250 genes (64.88%) predicted in the Z. rouxii genome, 5245 (99.90%) were annotated using NCBI Non-Redundant, UniProt, and InterProScan databases. The genome of the isolated Z. ruoxii harbored 2.03% of repeats and 0.68% of non-coding RNAs. Protein prediction indicated that β-glycosidases and hydroxynitrile lyase may play a key role in amygdalin degradation. The predicted degradation initiated by β-glycosidases that hydrolyze α-glucosidic bonds of amygdalin results in α-hydroxy nitriles (cyanohydrins) that are subsequently converted into carbonyl compounds (benzaldehyde) and hydrogen cyanide catalyzed by hydroxynitrile lyases. Present findings provide valuable data for constructing engineered microorganisms that can degrade amygdalin. Further analysis of Z. rouxii may elucidate the exact mechanism of amygdalin reduction in the production of maesil syrup.

Metal-free single heteroatom (N, O, and B)-doped coconut-shell biochar for enhancing the degradation of sulfathiazole antibiotics by peroxymonosulfate and its effects on bacterial community dynamics

Metal-free single heteroatom (N, O, and B)-doped coconut-shell biochar (denoted as N-CSBC, O-CSBC, and B-CSBC, respectively) were fabricated in a one-step pyrolysis process to promote peroxymonosulfate (PMS) activation for the elimination of sulfathiazole (STZ) from aquaculture water. B-CSBC exhibited remarkably high catalytic activity with 92% of STZ degradation in 30 min attributed to the presence of meso-/micro-pores and B-containing functional groups (including B-N, B-C, and B₂O₃ species). Radical quenching tests revealed SO₄^•-, HO•, and ¹O₂ being the major electron acceptors contributing to STZ removal by PMS over B-CSBC catalyst. The B-CSBC catalyst has demonstrated high sustainability in multiple consecutive treatment cycles. High salinity and the presence of inorganic ions such as chloride, enhanced the performance of the sulfate radical-carbon-driven advanced oxidation processes (SR-CAOPs) as pretreatment strategy that significantly facilitated the removal of STZ from aquaculture water. Furthermore, a potential sulfonamide-degrading microorganism, Cylindrospermum_stagnale, belonging to the phylum Cyanobacteria, was the dominant functional bacteria according to the results of high-throughput 16S rRNA gene sequencing conducted after the B-CSBC/PMS treatment. This study provides new insights into the SR-CAOP combined with bioprocesses for removing STZ from aqueous environments.

Indigenous bacterial consortium-mediated cypermethrin degradation in the presence of organic amendments and Zea mays plants

Cypermethrin is a toxic pyrethroid insecticide that is widely used in agricultural and household activities. One of the most serious issues is its persistence in the environment, because it is easily transported to the soil and aquatic ecosystem. The biodegradation of cypermethrin is emerging as an environmentally friendly method for large-scale treatment. This study examined the application of a novel binary bacterial combination-based (Bacillus thuringiensis strain SG4 and Bacillus sp. strain SG2) approach used for the enhanced degradation of cypermethrin from the environment. The bacterial strains degraded cypermethrin (80% and 85%) in the presence of external nitrogen sources (KNO₃ and NaNO₃). Furthermore, when immobilized in agar disc beads, the co-culture degraded cypermethrin (91.3%) with a half-life (t_1/2) of 4.3 days compared to 4.9 days using sodium alginate beads. Cereal straw, farmyard manure, press mud compost, fresh cow dung, and gypsum were used as organic amendments in the soil to stimulate cypermethrin degradation. Cereal straw promoted the fastest cypermethrin degradation among the different organic amendments tested, with a t_1/2 of 4.4 days. The impact of cypermethrin-degrading bacterial consortium on cypermethrin rhizoremediation was also investigated. Bacterial inoculums exhibited beneficial effects on plant biomass. Moreover, Zea mays and the bacterial partnership substantially enhanced cypermethrin degradation in soil. Six intermediate metabolites were detected during the degradation of cypermethrin, indicating that cypermethrin could be degraded first by the hydrolysis of its carboxyl ester bond, followed by the cleavage of the diaryl linkage and subsequent metabolism. Our findings highlight the promising potential and advantages of the bacterial consortium for the bioremediation of a cypermethrin-contaminated environment.

Current status of pesticide effects on environment, human health and it's eco-friendly management as bioremediation: A comprehensive review

Pesticides are either natural or chemically synthesized compounds that are used to control a variety of pests. These chemical compounds are used in a variety of sectors like food, forestry, agriculture and aquaculture. Pesticides shows their toxicity into the living systems. The World Health Organization (WHO) categorizes them based on their detrimental effects, emphasizing the relevance of public health. The usage can be minimized to a least level by using them sparingly with a complete grasp of their categorization, which is beneficial to both human health and the environment. In this review, we have discussed pesticides with respect to their global scenarios, such as worldwide distribution and environmental impacts. Major literature focused on potential uses of pesticides, classification according to their properties and toxicity and their adverse effect on natural system (soil and aquatic), water, plants (growth, metabolism, genotypic and phenotypic changes and impact on plants defense system), human health (genetic alteration, cancer, allergies, and asthma), and preserve food products. We have also described eco-friendly management strategies for pesticides as a green solution, including bacterial degradation, myco-remediation, phytoremediation, and microalgae-based bioremediation. The microbes, using catabolic enzymes for degradation of pesticides and clean-up from the environment. This review shows the importance of finding potent microbes, novel genes, and biotechnological applications for pesticide waste management to create a sustainable environment.

Whole genome sequencing and analysis of fenvalerate degrading bacteria Citrobacter freundii CD-9

Citrobacter freundii CD-9 is a Gram-negative bacteria sourced from factory sludge that can use fenvalerate as its sole carbon source and has a broad degradation spectrum for pyrethroid pesticides. The whole genome of CD-9 sequenced using Illumina HiSeq PE150 was reported in this study. The CD-9 genome size was 5.33 Mb and the G + C content was 51.55%. A total of 5291 coding genes, 9 5s-rRNA, and 79 tRNA were predicted bioinformatically. 3586 genes annotated to the Kyoto Encyclopedia of Genes and Genomes (KEGG) database that can be involved in 173 metabolic pathways, including various microbial metabolic pathways that degrade exogenous chemicals, especially those that degrade aromatic compounds, and also produce a variety of bioactive substances. Fifty genes related to pyrethroid degradation were identified in the C. freundii CD-9 genome, including 9 dioxygenase, 25 hydrolase, and 16 esterase genes. Notably, RT-qPCR results showed that from the predicted 13 genes related to fenvalerate degradation, the expression of six genes, including esterase, HAD family hydrolase, lipolytic enzyme, and gentisic acid dioxygenase, was induced in the presence of fenvalerate. In this study, the key genes and degradation mechanism of C. freundii CD-9 were analyzed and the results provide scientific evidence to support its application in environmental bioremediation. It can establish application models for different environmental pollution management by constructing genetically engineered bacteria for efficient fenvalerate or developing enzyme formulations that can be industrially produced.

Actinobacteria isolated from wastewater treatment plants located in the east-north of Algeria able to degrade pesticides

The pollution of water resources by pesticides poses serious problems for public health and the environment. In this study, Actinobacteria strains were isolated from three wastewater treatment plants (WWTPs) and were screened for their ability to degrade 17 pesticide compounds. Preliminary screening of 13 of the isolates of Actinobacteria allowed the selection of 12 strains with potential for the degradation of nine different pesticides as sole carbon source, including aliette, for which there are no previous reports of biodegradation. Evaluation of the bacterial growth and degradation kinetics of the pesticides 2,4-dichlorophenol (2,4-DCP) and thiamethoxam (tiam) by selected Actinobacteria strains was performed in liquid media. Strains Streptomyces sp. ML and Streptomyces sp. OV were able to degrade 45% of 2,4-DCP (50 mg/l) as the sole carbon source in 30 days and 84% of thiamethoxam (35 mg/l) in the presence of 10 mM of glucose in 18 days. The biodegradation of thiamethoxam by Actinobacteria strains was reported for the first time in this study. These strains are promising for use in bioremediation of ecosystems polluted by this type of pesticides.

Simultaneous biodegradation of λ-cyhalothrin pesticide and Vicia faba growth promotion under greenhouse conditions

λ-cyhalothrin is a widely used synthetic pyrethroid insecticide and its persistence in plant, soil and water exerts a detrimental effect on humans as well as the environment. There are many studies regarding isolated bacteria capable of degrading λ-cyhalothrin in vitro. However, limited work has been done examining the microbial degradation of λ-cyhalothrin together with plant growth promotion under greenhouse conditions. In this study, 43 bacterial strains were isolated from heavily polluted soil with λ-cyhalothrin by the enrichment technique. The plant growth promotion characteristics of all isolates were evaluated. The results revealed that five isolates were potential in λ-cyhalothrin biodegradation at high concentration (1200 mg/L) within only 24 h together with their high plant growth promotion abilities. The morphological, biochemical and 16S rDNA sequence analyses identified the isolates as Bacillus subtilis strains. The GC/MS analysis revealed that the selected isolates reached high levels of degradation after only two days, the degradation percentage ranged from 95.72 to 99.52% after 48 h of incubation. Furthermore, the degradation pathway for complete detoxification and metabolism of λ-cyhalothrin was established. Moreover, greenhouse experiment was conducted, the results indicate that the application of seed coat significantly enhanced Vicia faba seedling growth and caused an increase from 38.4 to 40.2% percentage of fresh and dry weight, respectively compared to untreated control. All isolates were effective to remove the pesticide residues in Vicia faba seedlings and recorded the highest degradation percentage of 83.79 under greenhouse conditions. Therefore, it can be concluded that the Bacillus subtilis strains isolated in this study have a dual potential role in complete mineralization of λ-cyhalothrin residues in vivo as well as effective biofertilization for future use in sustainable agriculture.

Microbe mediated remediation of dyes, explosive waste and polyaromatic hydrocarbons, pesticides and pharmaceuticals

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Environmental pollutants dyes, pesticides, pharmaceuticals, explosive waste and polyaromatic hydrocarbons.

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Environmental pollutants toxicity.

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Possible microbial biodegradation pathways of environmental pollutants.

Industrialization and human activities have led to serious effects on environment. With the progress taking place in the biodegradation field, it is important to summarize the latest advancement. In this review, we intend to provide insights on the recent progress on the biodegradation of environmental contaminants such as dyes, pesticides, pharmaceuticals, explosive waste and polyaromatic hydrocarbons by microorganisms. Along with the biodegradation of environmental contaminants, toxicity effects have also been discussed.

Analysis of Biodegradation of the Synthetic Pyrethroid Cypermethrin by Beauveria bassiana

Entomopathogenic fungi like Beauveria bassiana play a crucial role in natural control of arthropod pests which are being used in Integrated Pest Management programs. Assessing the compatibility of biological and chemical counterparts used in IPM programs is essential to achieve successful results in pest management. Behavior of four isolates of B. bassiana (ITCC 913, ARSEF 2860, ARSEF 1166, and ARSEF 3041) was tested in the presence of the pyrethroid insecticide cypermethrin. Spore germination and growth bioassays were conducted to assess the impact of cypermethrin on germination and growth. Though growth was not totally inhibited, there was retardation in the germination of spores and growth of the mycelium. Under this condition, ITCC 913 showed highest tolerance toward cypermethrin. Further analysis of the culture crude extracts by GC-MS revealed degradation of the insecticide by B. bassiana and putative intermediates of the degradation pathway were identified. This study reveals the potential of the entomopathogen B. bassiana in degradation of the pyrethroid insecticide cypermethrin. In conclusion, this potentiality of the studied fungus may help in the IPM strategies and find its role in degradation of such chemical pesticide compounds for utilization as a biodegradation agent further.

Evaluate the Toxicity of Pyrethroid Insecticide Cypermethrin before and after Biodegradation by Lysinibacillus cresolivuorans Strain HIS7

Herein, bacterial isolate HIS7 was obtained from contaminated soil and exhibited high efficacy to degrade pyrethroid insecticide cypermethrin. The HIS7 isolate was identified as Lysinibacillus cresolivuorans based on its morphology and physiology characteristics as well as sequencing of 16S rRNA. The biodegradation percentages of 2500 ppm cypermethrin increased from 57.7% to 86.9% after optimizing the environmental factors at incubation condition (static), incubation period (8-days), temperature (35 °C), pH (7), inoculum volume (3%), and the addition of extra-carbon (glucose) and nitrogen source (NH₄Cl₂). In soil, L. cresolivuorans HIS7 exhibited a high potential to degrade cypermethrin, where the degradation percentage increased from 54.7 to 93.1% after 7 to 42 days, respectively. The qualitative analysis showed that the bacterial degradation of cypermethrin in the soil was time-dependent. The High-Performance Liquid Chromatography (HPLC) analysis of the soil extract showed one peak for control at retention time (R.T.) of 3.460 min and appeared three peaks after bacterial degradation at retention time (R.T.) of 2.510, 2.878, and 3.230 min. The Gas chromatography-mass spectrometry (GC-MS) analysis confirmed the successful degradation of cypermethrin by L. cresolivuorans in the soil. The toxicity of biodegraded products was assessed on the growth performance of Zea mays using seed germination and greenhouse experiment and in vitro cytotoxic effect against normal Vero cells. Data showed the toxicity of biodegraded products was noticeably decreased as compared with that of cypermethrin before degradation.

Differential proteomic analysis under pesticides stress and normal conditions in Bacillus cereus 2D

A potential pesticide degrading bacterial isolate (2D), showing maximum tolerance (450 mg∙L^-1) for cypermethrin, fipronil, imidacloprid and sulfosulfuron was recovered from a pesticide contaminated agricultural field. The isolate degraded cypermethrin, imidacloprid, fipronil and sulfosulfuron in minimal salt medium with 94, 91, 89 and 86% respectively as revealed by high performance liquid chromatography (HPLC) and gas chromatography (GC) analysis after 15 days of incubation. Presence of cyclobutane, pyrrolidine, chloroacetic acid, formic acid and decyl ester as major intermediate metabolites of cypermethrin biodegradation was observed in gas chromatography mass spectrometry (GC-MS) analysis. Results based on 16S rDNA sequencing, and phylogenetic analysis showed maximum similarity of 2D with Bacillus cereus (Accession ID: MH341691). Stress responsive and catabolic/pesticide degrading proteins were over expressed in the presence of cypermethrin in bacteria. Enzymatic kinetics of laccase was deduced in the test isolate under normal and pesticide stress conditions which suggested that the production of enzyme was induced significantly in pesticide stress (163 μg.μL^-1) as compare to normal conditions(29 μg.μL^-1) while the K_m value was decreased in pesticides stress condition (K_m = 10.57 mM) and increases in normal condition (K_m = 14.33 mM).Amplification of laccase gene showed a major band of 1200bp. The present study highlights on the potential of 2D bacterial strain i.e., high tolerance level of pesticide, effective biodegradation rate, and presence of laccase gene in bacterial strain 2D, could become a potential biological agent for large-scale treatment of mixture of pesticide (cypermethrin, fipronil, imidacloprid and sulfosulfuron) in natural environment (soil and water).

Characterization of the role of esterases in the biodegradation of organophosphate, carbamate, and pyrethroid pesticides

Ester-containing organophosphate, carbamate, and pyrethroid (OCP) pesticides are used worldwide to minimize the impact of pests and increase agricultural production. The toxicity of these chemicals to humans and other organisms has been widely reported. Chemically, these pesticides share an ester bond in their parent structures. A particular group of hydrolases, known as esterases, can catalyze the first step in ester-bond hydrolysis, and this initial regulatory metabolic reaction accelerates the degradation of OCP pesticides. Esterases can be naturally found in plants, animals, and microorganisms. Previous research on the esterase enzyme mechanisms revealed that the active sites of esterases contain serine residues that catalyze reactions via a nucleophilic attack on the substrates. In this review, we have compiled the previous research on esterases from different sources to determine and summarize the current knowledge of their properties, classifications, structures, mechanisms, and their applications in the removal of pesticides from the environment. This review will enhance the understanding of the scientific community when studying esterases and their applications for the degradation of broad-spectrum ester-containing pesticides.

New Role for a Commercially Available Bioinsecticide: Bacillus thuringiensis Berliner Biodegrades the Pyrethroid Cypermethrin

The microbial diversity of several environments has been explored by researchers for the biodegradation of pyrethroids. In this study, a new approach was employed aiming at the use of Bacillus thuringiensis Berliner, a strain commercially available as bioinsecticide, for Cypermethrin (Cyp) biodegradation. This bacterial strain grew in the presence of Cyp and biodegraded this xenobiotic in a liquid medium. A central composite design for surface response methodology was employed for biodegradation. Under optimized conditions (50 mg·L^-1 of Cyp, pH 8.5, 37 °C), 83.5% biodegradation was determined with the production of 12.0 ± 0.6 mg·L^-1 3-phenoxybenzoic acid after 5 days. Moreover, a biodegradation pathway with the 18 compounds identified by GC-MS and LC-MS/MS was proposed. Experiments in soil for 28 days at 30 °C were performed, and 16.7% Cyp degradation was determined under abiotic conditions, whereas 36.6 ± 1.9% biodegradation was observed for B. thuringiensis Berliner with the native microbiome, indicating that bioaugmentation with this strain promoted a significant increase in the Cyp decontamination. Therefore, B. thuringiensis Berliner can act as biodegrader agent and insecticide at the same time, promoting decontamination of chemicals as Cyp while maintaining the protection of crops against insects. Moreover, B. thuringiensis species can produce bacteriocins with antifungal activity, which may increase agricultural productivity.

New insights into the degradation of synthetic pollutants in contaminated environments

The environment is contaminated by synthetic contaminants owing to their extensive applications globally. Hence, the removal of synthetic pollutants (SPs) from the environment has received widespread attention. Different remediation technologies have been investigated for their abilities to eliminate SPs from the ecosystem; these include photocatalysis, sonochemical techniques, nanoremediation, and bioremediation. SPs, which can be organic or inorganic, can be degraded by microbial metabolism at contaminated sites. Owing to their diverse metabolisms, microbes can adapt to a wide variety of environments. Several microbial strains have been reported for their bioremediation potential concerning synthetic chemical compounds. The selection of potential strains for large-scale removal of organic pollutants is an important research priority. Additionally, novel microbial consortia have been found to be capable of efficient degradation owing to their combined and co-metabolic activities. Microbial engineering is one of the most prominent and promising techniques for providing new opportunities to develop proficient microorganisms for various biological processes; here, we have targeted the SP-degrading mechanisms of microorganisms. This review provides an in-depth discussion of microbial engineering techniques that are used to enhance the removal of both organic and inorganic pollutants from different contaminated environments and under different conditions. The degradation of these pollutants is investigated using abiotic and biotic approaches; interestingly, biotic approaches based on microbial methods are preferable owing to their high potential for pollutant removal and cost-effectiveness.

Biotechnological basis of microbial consortia for the removal of pesticides from the environment

The application of microbial strains as axenic cultures has frequently been employed in a diverse range of sectors. In the natural environment, microbes exist as multispecies and perform better than monocultures. Cell signaling and communication pathways play a key role in engineering microbial consortia, because in a consortium, the microorganisms communicate via diffusible signal molecules. Mixed microbial cultures have gained little attention due to the lack of proper knowledge about their interactions with each other. Some ideas have been proposed to deal with and study various microbes when they live together as a community, for biotechnological application purposes. In natural environments, microbes can possess unique metabolic features. Therefore, microbial consortia divide the metabolic burden among strains in the group and robustly perform pesticide degradation. Synthetic microbial consortia can perform the desired functions at naturally contaminated sites. Therefore, in this article, special attention is paid to the microbial consortia and their function in the natural environment. This review comprehensively discusses the recent applications of microbial consortia in pesticide degradation and environmental bioremediation. Moreover, the future directions of synthetic consortia have been explored. The review also explores the future perspectives and new platforms for these approaches, besides highlighting the practical understanding of the scientific information behind consortia.

Biodegradation of hydrophobic pesticides by microalgae: Transformation products and impact on algae biochemical methane potential

Intensive and extensive use of pesticides has contributed to their wide distribution in soil, air, and water. Due to their detrimental effects on non-target organisms, different technologies have been considered for their removal. In this work, three hydrophobic pesticide active compounds, namely, chlorpyrifos, cypermethrin, and oxadiazon, were selected to study the potential for their removal from aqueous media by a microalgae consortium. An abiotic and a killed control (thermally inactivated dead microalgae biomass) were employed to clarify their removal pathways, and pesticide content was quantified in liquid and biomass phases for 7 days. At the final time, total degradation (biodegradation plus photodegradation) contributed to the removal of 55% of oxadiazon, 35% of chlorpyrifos, and 14% of cypermethrin. Furthermore, more than 60% of chlorpyrifos and cypermethrin were removed by sorption onto microalgae biomass. Overall, the three pesticides showed high removal from the liquid phase. O,O-diethyl thiophosphate was identified in the liquid phase as a transformation product of chlorpyrifos formed by microalgae degradation. Phycoremediation was coupled with anaerobic degradation of the microalgae biomass containing the retained pesticides by sorption through biochemical methane potential tests. Anaerobic digestion was not inhibited by the pesticides as verified by methane production yields. The removal efficiency of the pesticides in the digestate was as follows: chlorpyrifos > cypermethrin > oxadiazon. These results highlight the potential of low-cost algal-based systems for the treatment of wastewater or effluents from agrochemical industries. The integration of wastewater treatment with biogas production through anaerobic digestion is a biorefinery approach that facilitates the economic feasibility of the process.

Mechanism and application of Sesbania root-nodulating bacteria: an alternative for chemical fertilizers and sustainable development

Chemical fertilizers are used in large-scale throughout the globe to satisfy the food and feed requirement of the world. Demanding cropping with the enhanced application of chemical fertilizers, linked with a decline in the recycling of natural or other waste materials, has led to a decrease in the organic carbon levels in soils, impaired soil physical properties and shrinking soil microbial biodiversity. Sustenance and improvement of soil fertility are fundamental for comprehensive food security and ecological sustainability. To feed the large-scale growing population, the role of biofertilizers and their study tends to be an essential aspect globally. In this review, we have emphasized the nitrogen-fixing plants of Sesbania species. It is a plant that is able to accumulate nitrogen-rich biomass and used as a green manure, which help in soil amelioration. Problems of soil infertility due to salinity, alkalinity and waterlogging could be alleviated through the use of biologically fixed nitrogen by Sesbania plants leading to the conversion of futile land into a fertile one. A group of plant growth-promoting rhizobacteria termed as "rhizobia" are able to nodulate a variety of legumes including Sesbania. The host-specific rhizobial strains can be used as potential alternative for nitrogenous fertilizers as they help the host plant in growth and development and enhance their endurance under stressed conditions. The review gives the depth understanding of how the agriculturally important microorganisms can be used for the reduction of broad-scale application of chemical fertilizers with special attention to Sesbania-nodulating rhizobia.

Binding interaction of allethrin with esterase: Bioremediation potential and mechanism

The main aim of this work was to study the allethrin binding interactions with esterase and its bioremediation potential using an isolated bacterial strain CW7, identified as Pseudomonas nitroreducens. The degradation conditions with strain CW7 were optimized using response surface methodology at pH 7.0, a temperature of 32 °C, and an inocula concentration of 150 mg·L^-1, with 96% allethrin degradation observed over 7 days. The kinetic parameters q_max, K_s, and K_i were calculated to be 0.512 day^-1, 4.97 mg·L^-1, and 317.13 mg·L^-1, respectively. Nine intermediate metabolites were identified after analysing the degradation products by gas chromatography-mass spectrometry. Strain CW7 effectively degraded a wide variety of pyrethroids as a carbon source. Molecular modeling, docking, and enzyme kinetics were used to investigate the binding pocket of the esterase containing amino acids such as alanine, arginine, valine, proline, cysteine, glycine, isoleucine, phenylalanine, serine, asparagine, and threonine, which play active roles in allethrin degradation.

Biodegradation and metabolic pathway of fenvalerate by Citrobacter freundii CD-9

Fenvalerate is a pyrethroid insecticide with rapid action, strong targeting, broad spectrum, and high efficiency. However, continued use of fenvalerate has resulted in its widespread presence as a pollutant in surface streams and soils, causing serious environmental pollution. Pesticide residues in the soil are closely related to food safety, yet little is known regarding the kinetics and metabolic behaviors of fenvalerate. In this study, a fenvalerate-degrading microbial strain, CD-9, isolated from factory sludge, was identified as Citrobacter freundii based on morphological, physio-biochemical, and 16S rRNA sequence analysis. Response surface methodology analysis showed that the optimum conditions for fenvalerate degradation by CD-9 were pH 6.3, substrate concentration 77 mg/L, and inoculum amount 6% (v/v). Under these conditions, approximately 88% of fenvalerate present was degraded within 72 h of culture. Based on high-performance liquid chromatography and gas chromatography-mass spectrometry analysis, ten metabolites were confirmed after the degradation of fenvalerate by strain CD-9. Among them, o-phthalaldehyde is a new metabolite for fenvalerate degradation. Based on the identified metabolites, a possible degradation pathway of fenvalerate by C. freundii CD-9 was proposed. Furthermore, the enzyme localization method was used to study CD-9 bacteria and determine that its degrading enzyme is an intracellular enzyme. The degradation rate of fenvalerate by a crude enzyme solution for over 30 min was 73.87%. These results showed that strain CD-9 may be a suitable organism to eliminate environmental pollution by pyrethroid insecticides and provide a future reference for the preparation of microbial degradation agents and environmental remediation.

Bacilli-Mediated Degradation of Xenobiotic Compounds and Heavy Metals

Xenobiotic compounds are man-made compounds and widely used in dyes, drugs, pesticides, herbicides, insecticides, explosives, and other industrial chemicals. These compounds have been released into our soil and water due to anthropogenic activities and improper waste disposal practices and cause serious damage to aquatic and terrestrial ecosystems due to their toxic nature. The United States Environmental Protection Agency (USEPA) has listed several toxic substances as priority pollutants. Bacterial remediation is identified as an emerging technique to remove these substances from the environment. Many bacterial genera are actively involved in the degradation of toxic substances. Among the bacterial genera, the members of the genus Bacillus have a great potential to degrade or transform various toxic substances. Many Bacilli have been isolated and characterized by their ability to degrade or transform a wide range of compounds including both naturally occurring substances and xenobiotic compounds. This review describes the biodegradation potentials of Bacilli toward various toxic substances, including 4-chloro-2-nitrophenol, insecticides, pesticides, herbicides, explosives, drugs, polycyclic aromatic compounds, heavy metals, azo dyes, and aromatic acids. Besides, the advanced technologies used for bioremediation of environmental pollutants using Bacilli are also briefly described. This review will increase our understanding of Bacilli-mediated degradation of xenobiotic compounds and heavy metals.

Biodegradation of Allethrin by a Novel Fungus Fusarium proliferatum Strain CF2, Isolated from Contaminated Soils

Continuous use of allethrin has resulted in heavy environmental contamination and has raised public concern about its impact on human health, yet little is known about the kinetics and microbial degradation of this pesticide. This study reported the degradation kinetics in a novel fungal strain, Fusarium proliferatum CF2, isolated from contaminated agricultural fields. Strain CF2 utilized 50 mg·L-1 of allethrin as the sole carbon source for growth in minimal salt medium and tolerated high concentrations of allethrin of up to 1000 mg·L-1. The optimum degradation conditions for strain CF2 were determined to be a temperature of 26 °C and pH 6.0 using response surface methodology. Under optimum conditions, strain CF2 completely degraded allethrin within 144 hours. The degradation kinetics of allethrin followed first order reaction kinetics. Kinetics analysis showed that its half-life was substantially reduced by 507.1 hours, as compared to the uninoculated control. This study provides new insights into the microbial degradation of allethrin with fungal F. proliferatum CF2.

Esterase is a powerful tool for the biodegradation of pyrethroid insecticides

Agricultural and household applications of pyrethroid insecticides have significantly increased residual concentrations in living cells and environments. The enhanced concentration is toxic for living beings. Pyrethroid hydrolase enzyme (pyrethroid catalyzing esterase) regulates pyrethroid degradation, and has been well reported in various organisms (bacteria, fungi, insects and animals). Hydrolysis mechanisms of these esterases are different from others and properly function at factors viz., optimum temperature, pH and physicochemical environment. Active site of the enzyme contains common amino acids that play important role in pyrethroid catalysis. Immobilization technology emphasizes the development of better reusable efficiency of pyrethroid hydrolases to carry out large-scale applications for complete degradation of pyrethroids from the environments. In this review we have attempted to provide insights of pyrethroid-degrading esterases in different living systems along with complete mechanisms.

New insights into the microbial degradation and catalytic mechanism of synthetic pyrethroids

The significant applications of pyrethroid insecticides in agro-ecosystem and household environments have raised serious environmental concerns. Environmental bioremediation has emerged as an effective and eco-friendly approach to remove or neutralize hazardous compounds. Bioaugmentation accelerates pyrethroid degradation in liquid cultures and soil. Pyrethroid-degrading microorganisms have been extensively studied to cope with pyrethroid residues. Microorganisms primarily hydrolyze the ester bonds of pyrethroids, and their degradation pathways have been elaborated. The functional genes and enzymes involved in microbial degradation have also been screened and studied. Carboxylesterase plays a key role in pyrethroid degradation by cleaving its carboxylester linkage. The catalytic mechanism is dependent on a specific catalytic triad, consisting of three amino acid residues (glutamine, histidine, and serine) within the active site of the carboxylesterase enzyme. Pyrethroid-degrading strains and enzymes have proven to be effective for the bioremediation of pyrethroid-contaminated environments. In this review, we have summarized newly isolated pyrethroid-degrading strains and proposed the degradation pathways along with key functional genes/enzymes. To develop an efficient bioremediation strategy, pyrethroid-degrading microorganisms should be comprehensively explored.

Enhanced Cypermethrin Degradation Kinetics and Metabolic Pathway in Bacillus thuringiensis Strain SG4

Cypermethrin is popularly used as an insecticide in households and agricultural fields, resulting in serious environmental contamination. Rapid and effective techniques that minimize or remove insecticidal residues from the environment are urgently required. However, the currently available cypermethrin-degrading bacterial strains are suboptimal. We aimed to characterize the kinetics and metabolic pathway of highly efficient cypermethrin-degrading Bacillus thuringiensis strain SG4. Strain SG4 effectively degraded cypermethrin under different conditions. The maximum degradation was observed at 32 °C, pH 7.0, and a shaking speed of 110 rpm, and about 80% of the initial dose of cypermethrin (50 mg·L-1) was degraded in minimal salt medium within 15 days. SG4 cells immobilized with sodium alginate provided a higher degradation rate (85.0%) and lower half-life (t1/2) of 5.3 days compared to the 52.9 days of the control. Bioaugmentation of cypermethrin-contaminated soil slurry with strain SG4 significantly enhanced its biodegradation (83.3%). Analysis of the degradation products led to identification of nine metabolites of cypermethrin, which revealed that cypermethrin could be degraded first by cleavage of its ester bond, followed by degradation of the benzene ring, and subsequent metabolism. A new degradation pathway for cypermethrin was proposed based on analysis of the metabolites. We investigated the active role of B. thuringiensis strain SG4 in cypermethrin degradation under various conditions that could be applied in large-scale pollutant treatment.

Insight Into Microbial Applications for the Biodegradation of Pyrethroid Insecticides

Pyrethroids are broad-spectrum insecticides and presence of chiral carbon differentiates among various forms of pyrethroids. Microbial approaches have emerged as a popular solution to counter pyrethroid toxicity to marine life and mammals. Bacterial and fungal strains can effectively degrade pyrethroids into non-toxic compounds. Different strains of bacteria and fungi such as Bacillus spp., Raoultella ornithinolytica, Psudomonas flourescens, Brevibacterium sp., Acinetobactor sp., Aspergillus sp., Candida sp., Trichoderma sp., and Candia spp., are used for the biodegradation of pyrethroids. Hydrolysis of ester bond by enzyme esterase/carboxyl esterase is the initial step in pyrethroid biodegradation. Esterase is found in bacteria, fungi, insect and mammalian liver microsome cells that indicates its hydrolysis ability in living cells. Biodegradation pattern and detected metabolites reveal microbial consumption of pyrethroids as carbon and nitrogen source. In this review, we aim to explore pyrethroid degrading strains, enzymes and metabolites produced by microbial strains. This review paper covers in-depth knowledge of pyrethroids and recommends possible solutions to minimize their environmental toxicity.

The pyrethroid (±)-lambda-cyhalothrin enantioselective biodegradation by a bacterial consortium

Chiral pesticides have been used in agriculture, including (±)-lambda-cyhalothrin ((±)-LC), which is a pyrethroid insecticide widely employed on crops for protection against different types of insects. However, enantioselectivity is poorly studied in biodegradation processes. Therefore, the (±)-LC enantioselective biodegradation by bacteria from Brazilian savannah was reported in this study with a validated analytical method. All bacterial strains biodegraded (±)-LC with different efficiencies. Residual concentrations of LC (3.7-43.1% of biodegradation) and its enantiomeric excesses (0-27% ee) were determined. Additionally, the formation of the main biodegradation metabolite 3-phenoxybenzoic acid was also quantified. A Bacillus consortium composed of the three most efficient strains biodegraded more LC than any isolated strain solely employed in this work, showing that the use of a consortium is an interesting approach. In addition, 13 metabolites were identified and a biodegradation pathway with biochemical reactions of hydrolysis, reduction, esterification, amidation, elimination and group transfer were proposed, confirming the bioremediation potential of these strains. The LC stereoisomer with the highest insecticidal activity (1R,3R,αS-enantiomer, also known as gamma-cyhalothrin) was preferentially biodegraded by the studied bacteria. Therefore, crops protection with gamma-cyhalothrin, which can be applied in lower concentrations than (±)-LC because it is a more effective product against insects, may also be biodegraded faster than the racemic mixture in the environment, decreasing the toxic effects on non-target organisms.

Presence of esterase and laccase in Bacillus subtilis facilitates biodegradation and detoxification of cypermethrin

Ubiquitous presence of cypermethrin as a contaminant in surface stream and soil necessitates to develop potential bioremediation methods to degrade and eliminate this pollutant from the environment. A cypermethrin utilizing bacterial strain (MIC, 450  ppm) was isolated from the soil of pesticide contaminated agriculture field and characterized by using polyphasic approach. On molecular basis bacterial isolate showed 98% homology with Bacillus subtilis strain 1D. Under optimized growth conditions, bacteria showed 95% degradation of cypermethrin after 15 days and the end products of cypermethrin biodegradation under aerobic conditions were cyclododecylamine, phenol, 3-(2,2-dichloroethenyl 2,2-dimethyl cyclopropane carboxylate,1-decanol,chloroacetic acid, acetic acid, cyclopentan palmitoleic acid, and decanoic acid. Amplification of esterase (700 bp) and laccase (1200 bp) genes was confirmed by PCR which showed a possible role of these enzymes in biodegradation of cypermethrin. In the presence of cypermethrin Km value(s) of both the enzymes was low than the control. A nobel cypermethrin degradation pathway followed by B. subtilis was proposed on the basis of characterization of biodegraded products of cypermethrin using GC-MS. Cypermethrin biodegradation ability of Bacillus subtilis strain 1D without producing any toxic end product reveals the potential of this organism in cleaning of pesticide contaminated soil and water.

Screening of a beta-cypermethrin-degrading bacterial strain Brevibacillus parabrevis BCP-09 and its biochemical degradation pathway

A novel beta-cypermethrin (Beta-CP)-degrading strain isolated from activated sludge was identified as Brevibacillus parabrevis BCP-09 based on its morphological and physio-biochemical characteristics, and 16S rRNA gene analysis. Strain BCP-09 could effectively degrade Beta-CP at pH 5.0-9.0, 20-40 °C, and 10-500 mg L^-1 Beta-CP. Under optimal conditions (pH 7.41, 38.9 °C, 30.9 mg L^-1 Beta-CP), 75.87% Beta-CP was degraded within 3 days. Beta-CP degradation (half-life, 33.45 h) and strain BCP-09 growth were respectively described using first-order-kinetic and logistic-kinetic models. Seven metabolites were detected by high-performance liquid chromatography and gas chromatography-mass spectrometry- methyl salicylate, catechol, phthalic acid, salicylic acid, 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid, 3-phenoxybenzaldehyde, and 3-phenoxybenzoic acid (3-PBA). The major Beta-CP metabolite, 3-PBA was further degraded into phenol, benzoic acid, and 4-methylhexanoic acid. BCP-09 also degraded aromatic compounds such as phenol, catechol, and protocatechuic acid. Beta-CP appears to be mainly degraded into 3-PBA, which is continuously degraded into smaller benzene or chain compounds. Thus, strain BCP-09 could form a complete degradation system for Beta-CP and might be considered a promising strain for application in the bioremediation of environments and agricultural products polluted by Beta-CP.

Insilico Tools to Study the Bioremediation in Microorganisms

Bioinformatics is the new area of science to study various living organisms, plants and animals. Bioremediation is the removal of toxic pollutants from the environment using microorganisms. Many of the databases are available online and can be used for the study of the microorganism genomics, transcriptomics, proteomics. This chapter mainly focuses the uses of recent databases and tools for the exploration of microorganisms.

Toxicity evaluation of cypermethrin, glyphosate, and malathion, on two indigenous zooplanktonic species

In Aguascalientes, Mexico, there is a special concern about pesticides because of their intensive use on guava production areas, which are located in the vicinity of water reservoirs; thus, non-target organisms could be exposed. Thereafter, the aim of this work was to assess the effect of cypermethrin, Faena® (glyphosate), and malathion, which are the most used pesticides in Aguascalientes' guava production, on the indigenous freshwater species Alona guttata (cladoceran) and Lecane papuana (rotifer). Acute 48-h toxicity tests were carried out, and LC50 values were calculated. Then, five sublethal concentrations (1/80, 1/40, 1/20, 1/10, and 1/5 of the respective LC50) were selected for the chronic assays: (a) intrinsic growth rate analysis in the rotifer and (b) partial life table analysis in the cladoceran. The results of the acute toxicity tests showed that A. guttata was more sensitive to malathion (LC50 = 5.26 × 10-3 mg/L) at concentrations found in natural environments with continuous application on guava fields, whereas L. papuana was more sensitive to Faena® (LC50 = 19.89 mg/L). The somatic growth of A. guttata was inhibited for the chronic exposure to cypermethrin. In addition, cypermethrin and Faena® seemed to exert endocrine disruptive effects on A. guttata. Moreover, malathion chronic exposure significantly decreased the survival of A. guttata. Moreover, L. papuana was affected chronically for the three pesticides.

Differential expression and characterization of cypermethrin-degrading potential proteins in Bacillus thuringiensis strain, SG4

A cypermethrin-degrading bacterium (SG4) was isolated from the pesticide-contaminated soil in the agricultural field of the crop research centre of the University, and characterized as Bacillus thuringiensis strain, SG4. The bacterium degraded 78.9 % of cypermethrin (50 ppm) in 15 days when grown in a minimal medium. To understand the functional proteins of cypermethrin degradation in Bacillus thuringiensis strain SG4, a comparative proteomic analysis was performed in the presence/absence of cypermethrin after 5 days of incubation in minimal medium. More than 450 spots corresponding to different proteins were recorded by 2D electrophoresis. We report expression of 223 and 250 unique proteins under normal and induced conditions (cypermethrin stress), respectively. Identified proteins were categorized into different functional groups on the basis of their biological functions, viz., catabolic enzymes, translational and stress proteins, etc. Characterization of cypermethrin-specific proteins in a bacterial strain will help in biodegradation practices in situ.

Pyrethroid-Degrading Microorganisms and Their Potential for the Bioremediation of Contaminated Soils: A Review

Pyrethroid insecticides have been used to control pests in agriculture, forestry, horticulture, public health and for indoor home use for more than 20 years. Because pyrethroids were considered to be a safer alternative to organophosphate pesticides (OPs), their applications significantly increased when the use of OPs was banned or limited. Although, pyrethroids have agricultural benefits, their widespread and continuous use is a major problem as they pollute the terrestrial and aquatic environments and affect non-target organisms. Since pyrethroids are not degraded immediately after application and because their residues are detected in soils, there is an urgent need to remediate pyrethroid-polluted environments. Various remediation technologies have been developed for this purpose; however, bioremediation, which involves bioaugmentation and/or biostimulation and is a cost-effective and eco-friendly approach, has emerged as the most advantageous method for cleaning-up pesticide-contaminated soils. This review presents an overview of the microorganisms that have been isolated from pyrethroid-polluted sites, characterized and applied for the degradation of pyrethroids in liquid and soil media. The paper is focused on the microbial degradation of the pyrethroids that have been most commonly used for many years such as allethrin, bifenthrin, cyfluthrin, cyhalothrin, cypermethrin, deltamethrin, fenpropathrin, fenvalerate, and permethrin. Special attention is given to the bacterial strains from the genera Achromobacter, Acidomonas, Bacillus, Brevibacterium, Catellibacterium, Clostridium, Lysinibacillus, Micrococcus, Ochrobactrum, Pseudomonas, Serratia, Sphingobium, Streptomyces, and the fungal strains from the genera Aspergillus, Candida, Cladosporium, and Trichoderma, which are characterized by their ability to degrade various pyrethroids. Moreover, the current knowledge on the degradation pathways of pyrethroids, the enzymes that are involved in the cleavage of pesticide molecules, the factors/conditions that influence the survival of strains that are introduced into soil and the rate of the removal of pyrethroids are also discussed. This knowledge may be useful to optimize the environmental conditions of bioremediation and may be crucial for the effective removal of pyrethroids from polluted soils.