Transcriptomic profile in carbendazim-induced developmental defects in zebrafish (Danio rerio) embryos/larvae

Carbendazim is a widely used fungicide to protect agricultural and horticultural crops against a wide array of fungal species. Published reports have shown that the wide usage of carbendazim resulted in reprotoxicity, carcinogenicity, immunotoxicity, and developmental toxicity in mammalian models. However, studies related to the developmental toxicity of carbendazim in aquatic organisms are not clear. To address this gap, an attempt was made by exposing zebrafish embryos to carbendazim (800 μg/L) and assessing the phenotypic and transcriptomic profile at different developmental stages [24 hour post fertilization (hpf), 48 hpf, 72 hpf and 96 hpf). At 48 hpf, phenotypic abnormalities such as delay in hatching rate, deformed spinal axial curvature, and pericardial edema were observed in zebrafish larvae over its respective controls. At 72 hpf, exposure of zebrafish embryos exposed to carbendazim resulted in scoliosis; however, unexposed larvae did not exhibit signs of scoliosis. Interestingly, the transcriptomic analysis revealed a total of 1253 DEGs were observed at selected time points, while unique genes at 24 hpf, 48 hpf, 72 hpf and 96 hpf was found to be 76.54 %, 61.14 %, 92.98 %, and 68.28 %, respectively. Functional profiling of downregulated genes revealed altered transcriptomic markers associated with phototransduction (24 hpf and 72 hpf), immune system (48 hpf), and SNARE interactions in the vesicular pathway (96 hpf). Whereas functional profiling of upregulated genes revealed altered transcriptomic markers associated with riboflavin metabolism (24 hpf), basal transcription factors (48 hpf), insulin signaling pathway (72 hpf), and primary bile acid biosynthesis (96 hpf). Taken together, carbendazim-induced developmental toxicity could be ascribed to pleiotropic responses at the molecular level, which in turn might reflect phenotypic abnormalities.

Insights into enhanced toxic effects by the binary mixture of carbendazim and procymidone on hepatic lipid metabolism in mice

Carbendazim (CBZ) and procymidone (PRO) are two widely used fungicides in agriculture. However, there are still gaps in knowledge regarding about the potential hazards of joint exposure to CBZ and PRO in animals. Here, 6-week-old ICR mice were exposed to CBZ, PRO and CBZ + PRO for 30 days, and metabolomics were performed to discover the mechanism by which the mixture enhanced the effects on lipid metabolism. Co-exposure to CBZ + PRO elevated the body weights, relative liver weights and relative epididymis fat weights, but not in the single exposure groups. Molecular docking analysis suggested that CBZ and PRO combined with peroxisome proliferator-activated receptor (PPARγ) at the same amino acid site as the agonist rosiglitazone. The RT-qPCR and WB results demonstrated that the levels of PPARγ were higher in the co-exposure group than in the single exposure groups. In addition, hundreds of differential metabolites were discovered by metabolomics and enriched in different pathways, such as pentose phosphate pathway and purine metabolism. A unique effect, a decrease in glucose-6-phosphate (G6P) that promoted more NADPH production, was observed in the CBZ + PRO group. These results demonstrated that exposure to CBZ + PRO caused more serious lipid metabolism disorder in the liver than exposure to a single fungicide, which could provide some new insight for the toxic effects after fungicides joint exposure.

Carbendazim: Ecological risks, toxicities, degradation pathways and potential risks to human health

Carbendazim is a highly effective benzimidazole fungicide and is widely used throughout the world. The effects of carbendazim contamination on the biology and environment should be paid more attention. We reviewed the published papers to evaluate the biological and environmental risks of carbendazim residues. The carbendazim has been frequently detected in the soil, water, air, and food samples and disrupted the soil and water ecosystem balances and functions. The carbendazim could induce embryonic, reproductive, developmental and hematological toxicities to different model animals. The carbendazim contamination can be remediated by photodegradation and chemical and microbial degradation. The carbendazim could enter into human body through food, drinking water and skin contact. Most of the existing studies were completed in the laboratory, and further studies should be conducted to reveal the effects of successive carbendazim applications in the field.

L-carnitine extenuates endocrine disruption, inflammatory burst and oxidative stress in carbendazim-challenged male rats via upregulation of testicular StAR and FABP9, and downregulation of P38-MAPK pathways

We have addressed in the current study the potential of L-carnitine (LC) to extenuate the reproductive toxic insults of carbendazim (CBZ) in male rats, and the molecular mechanisms whereby carnitine would modify the spermatogenic and steroidogenic derangements invoked by the endocrine disruptor. Herein, animals received daily doses of carbendazim (100 mg/kg) by gavage for 8 weeks. Another CBZ-challenged group was co-supplemented with LC (500 mg/kg, IP) twice weekly for 8 weeks. Sperm quantity and quality (morphology, motility and viability), serum testosterone and gonadotropins, and thyroid hormone levels were assessed. Serum tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6) and interleukin-10 (IL-10) concentrations were determined by ELISA. Oxidant/antioxidant status in rat testis was investigated via measuring testicular contents of malondialdehyde (MDA) and reduced glutathione (GSH), as well as the activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx). Immunohistochemical localizations of the junctional protein; occludin, and inflammatory markers; inducible nitric oxide synthase (iNOS) and nuclear factor kappa beta (NF-κB) were further analyzed. A host of transduction genes that regulate spermatogenic and steroidogenic pathways, and their encoded proteins namely, Steroidogenic Acute Regulatory Protein (StAR), Fatty acid binding protein 9 (FABP9) and P38-mitogen activated protein kinase (P38-MAPK) were assessed by real time quantitative (RT-qPCR) and Western blot. LC improved rat spermiogram, testicular histological alterations and endocrine perturbances, and modulated genes' expressions and their respective proteins. In conclusion, LC effects appear to reside for the most part on its endocrine-preserving, anti-oxidant and anti-inflammatory properties through a myriad of interlaced signal transductions that ultimately recapitulated its beneficial effects on spermatogenesis and steroidogenesis.

Anchoring Metallic MoS2 Quantum Dots over MWCNTs for Highly Sensitive Detection of Postharvest Fungicide in Traditional Chinese Medicines

Carbendazim, a very common contamination to the traditional Chinese medicines (TCMs), has posed serious threat to the environment and human health. However, sensitive and selective detection of carbendazim (MBC) in the TCMs is a big challenge for their complex chemical constituents. In this work, a 0D/1D nanohybrid was developed by anchoring 1T-phased MoS₂ quantum dots (QDs) over multiwall carbon nanotubes (MWCNTs) via a facile assembly method. High-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis (TGA) together with EIS reveal that the 1T-phased QDs can anchor over MWCNTs via van der Waals forces, and the anchoring improves the nanohybrid surface area and conductivity. Therefore, the electrochemical sensor fabricated based on the MoS₂ QDs@MWCNT nanohybrid shows excellent catalytic activity to MBC oxidation. Under optimized conditions, the sensor presents a linear voltammetry response to MBC concentration from 0.04 to 1.00 μmol·L^-1, a low detection limit of 2.6 × 10^-8 mol·L^-1, as well as high selectivity, good reproducibility, and long-term stability. Moreover, the sensor has been successfully employed to determine MBC in two typical TCMs and the obtained recoveries are in good accordance with the results achieved by HPLC, showing that the constructed sensor plate holds great practical application in MBC analysis with complex matrix.

Sub-chronic carbendazim exposure induces hepatic glycolipid metabolism disorder accompanied by gut microbiota dysbiosis in adult zebrafish (Daino rerio)

Carbendazim (CBZ) as a broad spectrum fungicide is widely used in the whole world to contorl plant diseases. With the application of CBZ in the agriculture, it has been detected in vegetables and fruits. Nowadays, it even has been detected in the watercourse and indoor dust. However, the toxic effects of CBZ on aquatic organisms have received limited attention. In this study, male adult zebrafish were exposed at 0, 30 and 100 μg/L CBZ for 21 days to assess its effects on hepatic glycolipid metabolism. After exposure, the body weight and length decreased, but the condition factor increased significantly. Some hepatic biochemical parameters including the levels of glucose, pyruvate, low density lipoprotein (LDL) and triglyceride (TG) decreased significantly in the liver of zebrafish after exposure with CBZ. Two transaminases alanine transaminase (ALT) and aspartate transaminase (AST) also increased significantly, indicating that subchronic CBZ exposure influenced the liver function. Moreover, the relative mRNA levels of some key genes related to the glycolysis and lipid metabolism in the liver also changed significantly. Furthermore, the transcriptome analysis showed that the carbon metabolism, lipid metabolism and detoxification metabolism were also affected in the liver of CBZ exposed zebrafish. Interestingly, we also found the amounts of the Firmicutes, Bacteroidetes, Actinobacteria, α-Proteobacteria, γ-Proteobacteria and Verrucomicrobia at phylum level significantly decreased in the gut. Sequencing V3-V4 region of 16S rRNA also demonstrated gut microbiota composition changed significantly according to weighted UniFrac distance analysis. Consequently, subchronic CBZ exposure induced hepatic metabolic disorder accompanied by gut microbiota dysbiosis in adult male zebrafish.

Colorimetric determination of carbendazim based on the specific recognition of aptamer and the poly-diallyldimethylammonium chloride aggregation of gold nanoparticles

This paper proposes the idea of establishing carbendazim (CBZ) colorimetric determination in spiked water samples by specific aptamers of unlabeled carbendazim (CBZ), gold nanoparticles (AuNPs) and cationic polymer poly-diallyldimethylammonium chloride (PDDA). In the absence of CBZ, the CBZ aptamer will react with the cationic polymer PDDA by electrostatic interaction to form a complex structure. Therefore, the gold nanoparticles will remain dispersed due to the lack of PDDA. However, when CBZ is added into the sensory system, the CBZ-specific aptamer can selectively capture CBZ to form a stable complex structure. Due to the consumption of the aptamer, PDDA is unable to interact with the aptamer and begins to induce aggregation of AuNPs, thereby causing the color of the solution to change from red to blue. Colorimetric determination of CBZ based on the specific recognition of aptamer and the PDDA-induced aggregation of AuNPs has a detection limit of 2.2 nM, a linear range (R = 0.9960) from 2.2 to 500 nM. The method has good sensitivity and specificity, and the average recovery of CBZ is 94.9-104.8% in the application of actual water samples. This colorimetric method is simple, time-saving and low requirements for equipment, therefore, it holds great potential for CBZ detection in the environmental water samples.

Fluorescent aptasensor for carbendazim detection in aqueous samples based on gold nanoparticles quenching Rhodamine B

This paper proposes a fluorescent aptasensor for the detection of carbendazim (CBZ) in aqueous solution using CBZ-specific aptamer as sensing probe, gold nanoparticles (AuNPs) and Rhodamine B (RhoB) as indicator, respectively. In the absence of CBZ, CBZ aptamer could wrap AuNPs and maintained it dispersed in NaCl solution basically. Contrarily, the aptamer could specifically combine with CBZ and form a stable aptamer-CBZ complex, leaving AuNPs exposed to be aggregated by NaCl solution. The dispersed AuNPs could efficiently quench the fluorescence of RhoB, but those aggregated AuNPs have poor capability to impair the fluorescent indicator. Thus, the concentration of CBZ could be detected quantitatively through the distinction of the fluorescence intensity. This convenient fluorescent assay for CBZ had a wide linear range from 2.33 to 800 nM and a 2.33 nM limit of detection (LOD). Furthermore, it had high selectivity over pesticides, antibiotics, metal ions and other disrupting chemicals. As for application, the method could determine CBZ in water samples with recoveries in the range of 96.3-111.2%. This fluorescent aptasensor possessed great potential application for CBZ detection in actual aquatic environment.

Low dose carbendazim disrupts mouse spermatogenesis might Be through estrogen receptor related histone and DNA methylation

Pesticides, fungicides are reportedly involved in a decline in spermatozoa quality, especially motility, and a consequent increase in the rate of infertility. Fungicide carbendazim (CBZ) is widely used in agriculture and other aspects. Although CBZ is known to disrupt spermatogenesis, causing a decrease in spermatozoa concentration and motility, the mechanisms are not fully understood. We aimed to further explore the underlying mechanisms of CBZ disruption of spermatogenesis. Pubertal mice were exposed to low doses (0.1, 1 and 10 mg/kg body weight) of CBZ for 5 weeks, then many factors related to spermatogenesis have been explored. It was found that 0.1-10 mg/kg body weight of CBZ exposure decreased mouse sperm motility and concentration, diminished the important protein factors (VASA, PGK2, B-Amy and CREM) for spermatogenesis, reduced sperm protein acrosin level, disrupted very vital epigenetic factors H3K27, 5 mC and 5 hmC. Furthermore, CBZ exposure damaged estrogen receptor alpha (ERα) pathway by decreased the protein levels of ERα and its targets PI3K and AKT. In summary low doses of CBZ exposure disrupted mouse spermatogenesis through estrogen receptor signaling; and that histone methylation and DNA methylation might play vital roles in CBZ disturbance of spermatogenesis through intertwining with estrogen signaling pathways. CBZ from the contamination in environment or food chain poses a serious threat to the normal development of spermatozoa. Therefore we strongly recommend to minimise the use of CBZ since it causes the severe issues on spermatogenesis.

Therapeutic and fertility restoration effects of Ionidium suffruticosum on sub-fertile male albino Wistar rats: effects on testis and caudal spermatozoa

CONTEXT

Ionidium suffruticosum (L.) Ging (Violaceae) is an important medicinal plant widely used as a herbal traditional medicine in Ayurveda for the treatment of infertility. Currently, little pharmacological information is available on its male fertility properties following prolonged use.

OBJECTIVE

To investigate I. suffruticosum leaf extracts for male fertility parameters.

MATERIALS AND METHODS

The ethanol lyophilized fraction was administered orally on carbendazim-induced sub-fertility rats (250 mg/kg body weight for 28 days). The effects of fractions on rat's fertility parameters i.e., body and testes weight, sperm motility, sperm vitality, epididymal sperm counts, its morphology, enzyme and antioxidant stress and histopathology were studied and compared with clomiphene citrate.

RESULTS

The sub-fertile male rats treated with I. suffruticosum leaf extract increased the body weight of 7 g, testis weight of 97 mg, increased cauda epididymal sperm counts of 34.2 × 10⁶ sperm/mL, motility of sperm 46% and vitality 28% also increased and normal sperm morphology also improved up to 32%. The carbendazim-treated group showed loss in body weight of 33 g, testis weight of 851 mg, decreased epididymal sperm counts of 15 × 10⁶ sperm/mL, with sluggish motility and a highly significant fall in the live sperms of about 57%.

DISCUSSION AND CONCLUSION

The leaf fraction of I. suffructicosum increased the testicular weight, spermatogenesis, sperm counts, lessened sperm agglutination, and increased testicular oxidative biomarkers, SOD, and CAT. This study therefore supports the usage of I. suffructicosum in traditional medicine for infertility.

New experimental data on the human dermal absorption of Simazine and Carbendazim help to refine the assessment of human exposure

Due to their widespread usage, people are exposed to pesticides on a daily basis. Although these compounds may have adverse effects on their health, there is a gap in the data and the methodology needed to reliably quantify the risks of non-occupational human dermal exposure to pesticides. We used Franz cells and human skin in order to measure the dermal absorption kinetics (steady-state flux, lag time and permeability coefficient) of Carbendazim and Simazine. These parameters were then used to refine the dermal exposure model and a probabilistic simulation was used to quantify risks resulting from exposure to pesticide-polluted waters. The experimentally derived permeability coefficient was 0.0034 cm h(-1) for Carbendazim and 0.0047 cm h(-1) for Simazine. Two scenarios (varying exposure duration and concentration, i.e. environmentally relevant and maximum solubility) were used to quantify the human health risks (hazard quotients) for Carbendazim and Simazine. While no risks were determined in the case of either scenario, the permeability coefficient, which is concentration independent and donor, formulation, compound and membrane specific, may be used in other scenarios and exposure models to quantify more precisely the dermally absorbed dose during exposure to polluted water. To the best of our knowledge, the dermal absorption kinetics parameters defined here are being published for the first time. The usage of experimental permeability parameters in combination with probabilistic risk assessment thus provides a new tool for quantifying the risks of human dermal exposure to pesticides.

Reproductive and possible hormonal effects of carbendazim

This study aimed to better elucidate reproductive and possible hormonal effects of the fungicide carbendazim (CBZ) through a review of published toxicological studies as well as an evaluation of this fungicide in the Hershberger and uterotrophic assays, which are designed to detect in vivo effects of the sex hormones. The literature review indicates that CBZ induces reproductive and developmental toxicity through alteration of many key events which are important to spermatogenesis. The lower dose of CBZ (100mg/kg) evaluated in the Hershberger test increased prostate weight compared to control group but did not alter the weight of other testosterone-dependent tissues. In the uterotrophic assay, CBZ did not induce an estrogenic or an antiestrogenic effect. In the literature, it has been reported that CBZ may: (1) alter the levels of various hormones (testosterone, LH, FSH, GnRH); (2) negatively influence testicular steroidogenesis; (3) have androgenic effects acting directly in the androgenic receptors and/or increasing the expression of androgen receptors. Despite the contradictory results reported by the different studies that investigated a possible endocrine mode of action of CBZ, it seems that this fungicide may influence the hypothalamus-pituitary-gonad axis in addition to being a testicular toxicant.

Protective effect of Basella alba and Carpolobia alba extracts against maneb-induced male infertility

CONTEXT

Male infertility is one of the leading causes of social frustration and marginalization, mainly in the developing world. It is attributed to many factors including exposure to agropesticides such as manganese ethylenebis (dithiocarbamate) (maneb), which is one of the most frequently used fungicides in Cameroon. Previous reports support efficiency of some medicinal plants commonly used in Cameroonian folk medicine for the treatment of this disorder.

OBJECTIVE

The present study was aimed at assessing the protective effect of extracts from selected plant species, namely Basella alba L. (Basellaceae) (MEBa) and Carpolobia alba G. Don (Polygalaceae) (AECa), in alleviating the maneb-induced impairment of male reproductive function in Wistar albino rats.

MATERIALS AND METHODS

The rats were treated with vehicle, plant extract (MEBa or AECa), maneb and maneb plus plant extract, respectively, and their fertility was assessed. Animals were thereafter sacrificed and organs (liver, kidneys and reproductive organs) were dissected out and weighed. Serum androgens together with alanine aminotransferase, liver glutathione and thiobarbituric acid reactive species (TBARS) were also measured.

RESULTS AND DISCUSSION

From this study, both plant extracts stimulated testosterone and improved fertility. Administration of MEBa plus maneb prevented fertility reduction by maneb and minimized the inhibitory effect of maneb on testosterone levels. AECa also improved fertility of the maneb-exposed rats, though without restoring testosterone levels, and other investigated parameters remained unaffected by different treatments.

CONCLUSION

These findings emphasized the beneficial effects of B. alba and C. alba extracts on male fertility, and suggest their protective effect against maneb-induced toxicity in male reproductive function.

Kolaviron prevents carbendazim-induced steroidogenic dysfunction and apoptosis in testes of rats

The study evaluated the protective role of kolaviron (an isolated biflavonoid from the seed of Garcinia kola) and vitamin E in carbendazim-induced reproductive dysfunction in male rats. Adult male Wistar rats were orally exposed to carbendazim (200mg/kg) singly or in combination with kolaviron (100 and 200mg/kg). Exposure to carbendazim significantly decreased the activities of superoxide dismutase and catalase but markedly increased sialic acid concentration and lipid peroxidation in the testes of rats. Western blot analysis revealed that carbendazim treatment decreased the expression of steroid acute regulatory (StAR) protein and androgen binding protein (ABP) with concomitant decrease in activities of steroidogenic enzymes. Germ cell apoptosis in carbendazim-treated rats was confirmed by TUNEL assay. However, pretreatment with kolaviron and vitamin E restored the testicular antioxidant status and steroidogenesis and decreased apoptotic nuclei to near control level in carbendazim-treated rats. Kolaviron may prove useful in combating carbendazim-induced reproductive toxicity.

Sperm mRNA transcripts are indicators of sub-chronic low dose testicular injury in the Fischer 344 rat

Current human reproductive risk assessment methods rely on semen and serum hormone analyses, which are not easily comparable to the histopathological endpoints and mating studies used in animal testing. Because of these limitations, there is a need to develop universal evaluations that reliably reflect male reproductive function. We hypothesized that toxicant-induced testicular injury can be detected in sperm using mRNA transcripts as indicators of insult. To test this, we exposed adult male Fischer 344 rats to low doses of model testicular toxicants and classically characterized the testicular injury while simultaneously evaluating sperm mRNA transcripts from the same animals. Overall, this study aimed to: 1) identify sperm transcripts altered after exposure to the model testicular toxicant, 2,5-hexanedione (HD) using microarrays; 2) expand on the HD-induced transcript changes in a comprehensive time course experiment using qRT-PCR arrays; and 3) test these injury indicators after exposure to another model testicular toxicant, carbendazim (CBZ). Microarray analysis of HD-treated adult Fischer 344 rats identified 128 altered sperm mRNA transcripts when compared to control using linear models of microarray analysis (q<0.05). All transcript alterations disappeared after 3 months of post-exposure recovery. In the time course experiment, time-dependent alterations were observed for 12 candidate transcripts selected from the microarray data based upon fold change and biological relevance, and 8 of these transcripts remained significantly altered after the 3-month recovery period (p<0.05). In the last experiment, 8 candidate transcripts changed after exposure to CBZ (p<0.05). The two testicular toxicants produced distinct molecular signatures with only 4 overlapping transcripts between them, each occurring in opposite directions. Overall, these results suggest that sperm mRNA transcripts are indicators of low dose toxicant-induced testicular injury in the rat.

Carbendazim-induced testicular damage and oxidative stress in albino rats: ameliorative effect of licorice aqueous extract

Carbendazim is a broad spectrum carbamate fungicide used in the control of various fungal pathogens. Licorice ( Glycyrrhiza glabra) is one of the widely used medicinal plants in oriental nations. The present work studied the effect of licorice aqueous extract on carbendazim-induced testicular toxicity in albino rats. Administration of carbendazim induced significant decrease in testis weight, diameter, and germinal epithelial height of the seminiferous tubules. Histological results revealed degeneration of seminiferous tubules, loss of spermatogenic cells, and apoptosis. Moreover, carbendazim caused elevation of testicular malondialdehyde (MDA), marker of lipid peroxidation, and reduced the activity of the antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT). Coadministration of licorice extract with carbendazim improved the histomorphological and histopathological changes observed in animals treated with carbendazim. In addition, licorice treatment leads to a significant decrease in the level of MDA and increase in the activities of SOD and CAT. According to the present results, it is concluded that licorice aqueous extract can improve the testicular toxicity of carbendazim and this effect may be attributed to antioxidant properties of one or more of its constituents.

Male reprotoxicity and endocrine disruption

Mammalian reproductive tract development is a tightly regulated process that can be disrupted following exposure to drugs, toxicants, endocrine-disrupting chemicals (EDCs), or other compounds via alterations to gene and protein expression or epigenetic regulation. Indeed, the impacts of developmental exposure to certain toxicants may not be fully realized until puberty or adulthood when the reproductive tract becomes sexually mature and altered functionality is manifested. Exposures that occur later in life, once development is complete, can also disrupt the intricate hormonal and paracrine interactions responsible for adult functions, such as spermatogenesis. In this chapter, the biology and toxicology of the male reproductive tract is explored, proceeding through the various life stages including in utero development, puberty, adulthood, and senescence. Special attention is given to the discussion of EDCs, chemical mixtures, low-dose effects, transgenerational effects, and potential exposure-related causes of male reproductive tract cancers.

Cloning and biochemical characterization of a novel carbendazim (methyl-1H-benzimidazol-2-ylcarbamate)-hydrolyzing esterase from the newly isolated Nocardioides sp. strain SG-4G and its potential for use in enzymatic bioremediation

A highly efficient carbendazim (methyl-1H-benzimidazol-2-ylcarbamate, or MBC)-mineralizing bacterium was isolated from enrichment cultures originating from MBC-contaminated soil samples. This bacterium, Nocardioides sp. strain SG-4G, hydrolyzed MBC to 2-aminobenzimidazole, which in turn was converted to the previously unknown metabolite 2-hydroxybenzimidazole. The initial steps of this novel metabolic pathway were confirmed by growth and enzyme assays and liquid chromatography-mass spectrometry (LC-MS) studies. The enzyme responsible for carrying out the first step was purified and subjected to N-terminal and internal peptide sequencing. The cognate gene, named mheI (for MBC-hydrolyzing enzyme), was cloned using a reverse genetics approach. The MheI enzyme was found to be a serine hydrolase of 242 amino acid residues. Its nearest known relative is an uncharacterized hypothetical protein with only 40% amino acid identity to it. Codon optimized mheI was heterologously expressed in Escherichia coli, and the His-tagged enzyme was purified and biochemically characterized. The enzyme has a K(m) and k(cat) of 6.1 muM and 170 min(-1), respectively, for MBC. Radiation-killed, freeze-dried SG-4G cells showed strong and stable MBC detoxification activity suitable for use in enzymatic bioremediation applications.