Determination of aldicarb, carbofuran and some of their main metabolites in groundwater by application of micellar electrokinetic capillary chromatography with diode-array detection and solid-phase extraction

This paper describes a UV detection method for the pesticides aldicarb and carbofuran, and some of their main metabolites, aldicarb-sulfoxide, aldicarb-sulfone and 3-hydroxy-carbofuran, in ground waters. Micellar electrokinetic chromatography (MEKC) with diode-array detection was developed for their determination at 210 nm. The experimental study was performed using sodium dodecyl sulfate (SDS) at a concentration level of 140 mM, and a buffer of borax/HCl 20 mM at pH 8 which gives the best resolution with an analysis time of less than 20 min. Different instrumental parameters such as voltage (23 kV), injection time (12 s) and temperature (25 degrees C) were optimized. The detection limits were in the range 2-7.4 microg glitre(-1) by solid-phase extraction (SPE) with a subsequent evaporation step. Groundwater spiked samples were pre-concentrated off-line with graphite carbon and subsequently analyzed by MEKC with diode-array detection yielding average recoveries between 77 and 97% (n = 4) with RSD between 2-7%.

Sphingomonas sp. strain SB5 degrades carbofuran to a new metabolite by hydrolysis at the furanyl ring

Microorganisms capable of degrading carbofuran were isolated from soils and examined for the degradation of this pesticide at ring structure. An isolate that could degrade carbofuran and carbofuran-7-phenol was selected for further studies. The 16S rRNA analysis results showed that the isolate belongs to the genus of Sphingomonas, close to dioxin and dicamba degraders, and is named Sphingomonas sp. SB5. SB5 did not show any similarity of 16S rRNA to known carbofuran degraders. When time-course degradation of carbofuran by SB5 was examined by solvent extraction combined with liquid chromatographic analysis, almost complete disappearance of carbofuran was observed within 12 h, giving several accumulative metabolites. Bacterial cultures incubated with carbofuran-7-phenol suggested that the accumulated metabolites were derived from carbofuran-7-phenol. The control without SB5 and kanamycin-treated SB5 did not show any metabolite, suggesting a biological involvement in the degradation of carbofuran. GC/MS and LC/MS analyses identified 2-hydroxy-3-(3-methylpropan-2-ol) phenol as one of the accumulated metabolites, suggesting that the strain SB5 could degrade carbofuran-7-phenol by hydrolysis at the furanyl ring. This is the first report to identify 2-hydroxy-3-(3-methylpropan-2-ol) phenol as a new product derived biologically from carbofuran-7-phenol.

Characterization of a novel carbofuran degradingPseudomonassp. with collateral biocontrol and plant growth promoting potential

The isolate NJ-101 obtained from agricultural soil was characterized and presumptively identified as Pseudomonas sp. The isolate exhibited efficient degradation of the insecticide carbofuran with a rate constant of 0.035 day(-1), following first-order rate kinetics. The ability of performing multifarious biological activities in tandem suggested the uniqueness of isolate NJ-101. The ability to produce hydrogen cyanide and siderophore stipulated its role in biological control. Furthermore, the growth inhibition of Fusarium sp. validated the antagonistic activity of NJ-101 against the common phytopathogens. Concurrent production of indole acetic acid, and solubilization of inorganic phosphate revealed its plant growth promoting potential. Thus, the innate capability of this novel isolate for parallel biodegradation, biocontrol and plant growth promotion has significance in management of the agro-environmental and phytopathological problems.

Genetic transfer of the mcd gene in soil

AIMS

To investigate the role of horizontal gene transfer of mcd (methylcarbamate-degrading) gene in high genetic diversity of carbofuran-degrading bacteria.

METHODS AND RESULTS

The actuality of genetic transfer from degraders to an Agrobacterium tumefaciens strain was determined in liquid medium. The mcd gene was chosen for transfer experiments. Transconjugants were obtained irrespective of the type of the donor strain (Gram-positive or Gram-negative), size of the inoculum, or nature and concentration of the pesticide in the medium. Soil microcosms, inoculated with or without the donor and/or recipient strains were used. The size of the initial degrading population (treated or untreated soil) and the nature of the inoculated donor strains were considered. More transconjugants were isolated in the previously treated soil than in the untreated soil. Agrobacterium transconjugants were isolated even when the donor strain was not inoculated, probably as a result of gene transfer from indigenous degrading population to the recipient strain. Moreover, potential transconjugants belonging to the Pseudomonas genus were isolated.

CONCLUSIONS

Our results seem to demonstrate that the mcd gene is transferable in soil among bacterial populations.

SIGNIFICANCE AND IMPACTS OF THE STUDY

The transfer of the mcd gene is partly responsible for the high genetic diversity of micro-organisms able to catabolize carbofuran.

Induction of carbofuran oxidation to 4-hydroxycarbofuran by Pseudomonas sp. 50432

Pseudomonas sp. 50432 biotransformed a highly toxic pesticide, carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) to 7-phenol (2,3-dihydro-2,2-dimethyl-7-hydroxy benzofuran) and several unknown metabolites. One of the unknown metabolites identified by gas chromatography/mass spectroscopy was 4-hydroxycarbofuran (2,3-dihydro-2,2-dimethyl-4-hydroxybenzofuran-7-yl methylcarbamate). It had a mass (237) similar to 3-hydroxycarbofuran and 5-hydroxycarbofuran but different fragmentation patterns. This is the first report in which an inducible oxidative enzyme, hydroxylase, mediated the conversion of carbofuran to 4-hydroxycarbofuran. A second constitutively synthesized enzyme hyrolase transformed carbofuran to 7-phenol.

Dermal pharmacokinetics of the insecticide furathiocarb in rats

The pharmacokinetics of furathiocarb were studied in vivo in male Sprague-Dawley rats following dermal treatment. HPLC and post-column derivatization were used for the analysis of furathiocarb and its metabolites (carbofuran, 3-hydroxycarbofuran and 3-ketocarbofuran). Carbofuran and 3-hydroxycarbofuran were detected in plasma and urine rather than furathiocarb. 3-Ketocarbofuran, another potential metabolite, was not observed in any sample. The concentration of carbofuran was higher than that of 3-hydroxycarbofuran in plasma, but the reverse was the case in urine. The corresponding area under the plasma concentration-time curve, Tmax, and Cmax values of carbofuran and 3-hydroxycarbofuran for 1500 mg kg-1 doses were 2.4-8.0 mg equiv hml-1, 12 h and 0.1-0.4 mg equiv ml-1, respectively. T1/2 was calculated only for 3-hydroxycarbofuran (28 h). Two metabolites were excreted in a dose-dependent manner without saturation.

The effect of initial concentration of carbofuran on the development and stability of its enhanced biodegradation in top-soil and sub-soil

Carbofuran was incubated in top-soil and sub-soil samples from a pesticide-free site at a range of initial concentrations from 0.1 to 10 mg kg-1. Amounts of the incubated soils were removed at intervals over the subsequent 12 months, and the rate of degradation of a second carbofuran dose at 10 mg kg-1 was assessed. An applied concentration as low as 0.1 mg kg-1 to top-soil resulted in more rapid degradation of the fresh addition of carbofuran for at least 12 months. The degree of enhancement was generally more pronounced with the higher initial concentrations. When the same study was conducted in sub-soil samples from the same site, an initial dose of carbofuran at 0.1 mg kg-1 resulted in only small increases in rates of degradation of a second carbofuran dose. However, degradation rates in the sub-soil samples were, in many instances, considerably greater than in the corresponding top-soil samples, irrespective of pre-treatment concentration or pre-incubated period. Initial doses of 0.5 mg kg-1 and higher applied to sub-soil successfully activated the sub-soil microflora. Application of the VARLEACH model to simulate carbofuran movement through the soil profile indicated that approximately 0.01 mg kg-1 of carbofuran may reach a depth of 70 cm 400 days after a standard field application. The results therefore imply that adaptation of the sub-soil microflora (c 1 m depth) by normal field rate applications of carbofuran is unlikely to occur. In experiments to investigate this in soils exposed to carbofuran in the field, there was no apparent relationship between top-soil exposure and degradation rates in the corresponding sub-soils. The results further confirmed that same sub-soil samples have an inherent capacity for rapid biodegradation of carbofuran. The high levels of variability observed between replicates in some of the sub-soil samples were attributed to the uneven distribution of a low population of carbofuran-degrading micro-organisms in sub-surface soil. There was no apparent relationship between soil microbial biomass and degradation rates within or between top-soil and sub-soil samples.

Isolation and characterization of 23 carbofuran-degrading bacteria from soils from distant geographical areas

The aim of this work was to isolate, identify and type carbofuran-degrading bacteria from two geographically distant soils. Restriction Fragment Length Polymorphism (RFLP) patterns of the 16S rRNA gene and partial 16S rRNA sequence analysis were used to classify the 23 isolates obtained. Nine of them showed high similarity to Pseudomonas strains, seven showed similarity to the Flexibacter/Cytophaga/Bacteroides group and the remainder showed similarity to other bacterial genera. Isolates within the same group were sub-typed by comparing partial 16S rRNA sequences and SDS-PAGE analysis of their total protein profiles. Many of the UK isolates showed similarity to the Pseudomonas genera, while most of the Greek isolates showed similarity to the Flexibacter/Cytophaga/Bacteroides group. Only two Chrysobacterium strains isolated from both the UK and Greek soils were identical.

Microbial degradation of carbosulfan by carbosulfan--and carbofuran-retreated rice soil suspension

The role of microorganisms in the degradation of carbosulfan (2,3-dihydro-2,2-dimethyl-7-benzofuranyl-(di-n-butyl)-aminosulfenyl++ + methyl carbamate), an analogue of carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl-N-methyl carbamate) was studied by selective enrichment of microorganisms degrading either or both insecticides by repeated application of the insecticides, individually or in combination to flooded soil. Soil suspension from the pots treated with carbosulfan and carbofuran, individually or in combination collected after two applications, effected distinctly more rapid hydrolysis of carbosulfan than did the suspension from untreated pots or the uninoculated medium. The rate of hydrolysis was further accelerated by soil suspensions collected after six applications of the insecticides in the order carbosulfan treated > carbofuran treated > carbosulfan + carbofuran treated. The ability of treated and untreated suspension to degrade carbofuran was also studied. The rate of degradation of carbofuran by the suspension was in the order carbofuran retreated > carbosulfan + carbofuran retreated > carbosulfan retreated soil. Further involvement of microorganism in the rapid degradation of carbosulfan was confirmed by testing the degradation in sterilized and nonsterilized enrichment culture.

Metabolism of carbofuran by Aspergillus niger and Fusarium graminearum

Metabolism of carbofuran in pure liquid cultures of A. niger and F. graminearum was investigated. Carbofuran and its metabolites were analyzed by HPLC and TLC. The average recoveries of carbofuran, 3-hydroxycarbofuran, 3-ketocarbofuran, and 3-ketocarbofuran phenol from fungi media were found to be 88.65, 86.19, 75.48, and 80.48%, while their detection limits were 0.035, 0.031, 0.015 and 0.140 ppm, respectively. The data showed that A. niger was capable of degrading carbofuran more faster than F. graminearum. Carbofuran disappeared biexponentially from the liquid culture media of both fungi. The terminal half-life values of carbofuran were 10.4 and 12 days in the media of A. niger and F. graminearum, respectively. The amounts of carbofuran reached 15.56 and 19.71% of the applied dose after 21 days in case of A. niger and F. graminearum, respectively. Carbofuran was biotransformed to 3-hydroxycarbofuran, 3-ketocarbofuran, and 3-ketocarbofuran phenol. The percentages of the major metabolite, 3-hydroxycarbofuran were 47.72 and 7.77% in case of A. niger and F. graminearum after 21 days, respectively.

Mutagenic and genotoxic activities of four pesticides: captan, foltaf, phosphamidon and furadan

The mutagenic and genotoxic potential of four pesticides viz. captan, foltaf, phosphamidon and furadan was evaluated by the Ames mutagenicity assay and their DNA damaging ability on radiation repair defective E. coli K-12 strains respectively. The mutagenic spectrum revealed captan to be most mutagenic in the absence of metabolic activation, while the presence of S9 mix led to an attenuated mutagenic response. Foltaf, phosphamidon and furadan were detected as relatively weaker mutagens. A significant decrease in the survival of SOS defective mutants, recA, lexA and pol- of E. coli was observed as compared to their wild-type counterparts in the presence of the pesticides. The role of SOS repair genes gains further support from the Salmonella strains triggering the error-prone SOS response.

Plasmid-mediated mineralization of carbofuran by Sphingomonas sp. strain CF06

A bacterial strain (CF06) that mineralized both the carbonyl group and the aromatic ring of the insecticide carbofuran and that is capable of using carbofuran as a sole source of carbon and nitrogen was isolated from a soil in Washington state. Phospholipid fatty acid and 16S rRNA sequencing analysis indicate that CF06 is a Sphingomonas sp. CF06 contains five plasmids, at least some of which are required for metabolism of carbofuran. Loss of the plasmids induced by growth at 42 degrees C resulted in the inability of the cured strain to grow on carbofuran as a sole source of carbon. Introduction of the plasmids confers on Pseudomonas fluorescens M480R the ability to use carbofuran as a sole source of carbon for growth and energy. Of the five plasmids, four are rich in insertion sequence elements and contain large regions of overlap. Rearrangements, deletions, and loss of individual plasmids that resulted in the loss of the carbofuran-degrading phenotype were observed following introduction of Tn5.

Cloning and sequence analysis of a novel insertion element from plasmids harbored by the carbofuran-degrading bacterium, Sphingomonas sp. CFO6

Sphingomonas sp. CFO6 (a member of the alpha group of Proteobacteria) was isolated from a Washington soil by enrichment on the insecticide carbofuran as a sole source of carbon and energy. This strain has been shown to harbor five plasmids, at least some of which are required for catabolism of carbofuran. Rearrangements, deletions, and loss of individual plasmids resulting in the loss of the carbofuran-degrading phenotype were observed following treatment with heat or introduction of Tn5. Several putative insertion sequence elements of different sizes were cloned from these plasmids by trapping in pUCD800, a positive selection vector for isolation of transposable elements. Three of the most common putative IS elements (designated IS1412, IS1487, and IS1488) in the clone library were of different sizes and cross-hybridize with each other. An element hybridizing with IS1412, IS1487, and IS1488 was mobilized during growth of CFO6 at 42 degrees C and inserted into one of CFO6's plasmids (pCFO4), corresponding to a deletion in the plasmid and a loss of catabolic function. IS1412 was completely sequenced and its sequence analyzed. IS1412 is 1656 bp in length and possesses terminal partially matched inverted repeats of unequal length (17 and 18 bp). In addition, IS1412 contains an open reading frame which encodes a putative transposase with significant homology to the putative transposases of IS1380 from Acetobacter pasteurianus, HRS1 from Bradyrhizobium japonicum, and IS1247 from Xanthobacter autotrophicus. These related IS elements form part of a family of common IS elements distributed among members of the alpha group of the Proteobacteria.

Behavioral effects of waterborne carbofuran in goldfish

The effects of concentration (1, 10, 100 microg/L) and duration (4, 8, 12 h) of exposure to carbofuran were assessed on the swimming activity, social interactions, and behavioral responses of goldfish to a flow (0.1 L/min) of water, with or without chironomids. Observations were also made on the behavioral responses of unexposed goldfish to a flow (0.1 L/min) of carbofuran-contaminated water. A 4-h exposure of goldfish 1 microg/L carbofuran produced a significant increase in sheltering, burst swimming, and nipping. Responses were enhanced at 100 microg/L. After a 12-h exposure, the behavioral effects of 1 microg/L carbofuran were less apparent. However, burst swimming at 10 microg/L, and sheltering, nipping and burst swimming at 100 microg/L, were still significantly increased after a 12-h exposure to carbofuran. Grouping was not consistently affected by exposure conditions. Chemical attraction to a filtrate of chironomids was significantly reduced after the 4-h exposure to 1 microg/L carbofuran. Decreased attraction to the food extract was less apparent after the 12-h exposure, except at 100 microg/L carbofuran. A significant decrease in attraction to a flow of uncontaminated water was also observed after a 4-h exposure to 10 and 100 microg/L carbofuran. Unexposed goldfish did not show avoidance reaction to a flow of carbofuran-contaminated water, even at a concentration (10 mg/L) exceeding the mean 96-h LC-50 in cyprinids (0.5-1 mg/L). However, at all concentrations tested (0.1, 1, 10 mg/L), goldfish quickly reacted to the introduction of the solution of carbofuran by increased burst swimming and nipping. These results are discussed in the light of the data concerning behavioral and neurotoxic effects of carbamate and organophosphorous insecticides in fish.

Pesticide poisoning of animals of wild fauna

Poisoning of rare birds of prey (7 Aegipius monachus and 1 Aquila chrysaetus) and 11 foxes by carbofuran is reported. The poisoning is an ecological disaster because of the death of A monachus, which is a rare species. Identification, confirmation and distribution of the toxic substance was performed by TLC and HPLC techniques.

Environmental fate of rice pesticides in California

Each of the pesticides reviewed is reported to dissipate from field water after application. Carbofuran is hydrolyzed rapidly under the alkaline conditions usually found in the rice field environment, and its hydrolysis products are also degraded rapidly. The longest half-life reported (18-26 d) was in water that overlaid soil treated with Furadan granular formulation. Generally, carbofuran dissipation ranged from 36 hr to 3 d. Under field application, bensulfuron methyl showed a half-life of 1-3 d, but others have recovered all of the "dissipated" herbicide in the soil compartment. MCPA applied to rice fields is reportedly degraded by the joint action of sunlight and microbial action with a half-life of 3-5 d. Methyl parathion showed a maximum half-life of 9-17 d in a model aquatic ecosystem, but other reports found more rapid dissipation. The half-life of molinate has been observed by numerous researchers to be less than 5 d, with volatility the major route of loss. A half-life as short as 5-7 d has been reported for thiobencarb applied to rice fields, but others report much longer periods; volatility again is expected to be a significant route of loss. Microbial degradation takes place with each of the subject pesticides. Numerous authors have reported enhanced degradation of carbofuran under conditions of repeated application, and this probably holds true for the others. A specialized segment of the microbial population (Pseudomonas spp.) is purported to carry out most of the degradation but is inefficient at degrading the hydrolysis product, carbofuran phenol. Biodegradation of bensulfuron methyl has been observed with actinomycetes, fungi, and bacteria, and takes place primarily by oxidation and hydrolysis. Methyl parathion is biodegraded primarily by nitro reduction to aminomethyl parathion. A fungus, an actinomycete, and a bacterium were shown to biodegrade molinate, primarily by oxidation at the sulfur atom and the azepine ring. Thiobencarb is biodegraded in anaerobic sediments at a slow rate; the dechlorinated thiobencarb was shown to cause dwarfing of rice in some fields. Otherwise, its aerobic biodegradation is rapid and follows the same routes as with molinate. Carbofuran is a systemic insecticide that is rapidly absorbed and translocated to aerial parts of the plant. Carbofuran is metabolized in rice plants to the corresponding phenol, which is irreversibly bound into the plant, as well as to 3-hydroxycarbofuran and other minor components; it is depurated through leaf exudate, from which it volatilizes. Rice plants were observed to take up more bensulfuron methyl through shoots than roots and to metabolize it to the 4-hydroxy analog. The half-life of methyl parathion in Hydrilla verticulla, an aquatic macrophyte, was 1 wk, but little has been reported on methyl parathion in plants. Barnyardgrass was found to absorb greater amounts of molinate than did rice, and it produced larger proportions of basic metabolites, which may form the basis for its selective toxicity. Thiobencarb has been shown to be rapidly absorbed, translocated, and metabolized in rice plants, barnyardgrass, and the broadleaved wild amaranth, smartweed, and lambsquarters. Translocation was more rapid and extensive in barnyardgrass than in rice, and most of the 14C radiolabel was recovered as metabolites. Its terminal metabolite, chlorobenzoic acid, was taken up into lignin-like plant constituents. It is apparent that information on plant uptake and biodegradation is limited--none exists for woody species--but the fact that some species appear resistant to the herbicides suggests that biodegradative ability is general. (ABSTRACT TRUNCATED)

Carbofuran toxicity

Carbofuran, an anticholinesterase carbamate, is commonly used as an insecticide, nematicide, and acaricide in agricultural practice throughout the world. Due to its widespread use in agriculture, contamination of food, water, and air has become imminent, and consequently adverse health effects are inevitable in humans, animals, wildlife, and fish. Currently, carbofuran's involvement is most frequently encountered in malicious poisoning. The literature on chemical properties, acute toxicity data, poisoning incidences, pharmacokinetics, and mechanism of toxicity of carbofuran is briefly reviewed. Much emphasis is given to the metabolism of carbofuran, and the impact of carbofuran and its two major metabolites (3-hydroxycarbofuran and 3-ketocarbofuran) on overall toxicity. Biochemical (cholinergic and noncholinergic), hematological, and immunological effects induced by carbofuran are discussed in detail. Carbofuran and/or its major metabolites can cross the placental barrier and produce serious effects on the maternal-placental-fetal unit. Carbofuran's toxicity can be potentiated by simultaneous exposure with other cholinesterase inhibitors. Literature on various biomarkers of carbofuran exposure and on induced adverse health effects is also presented. To date, a combination of atropine and memantine remains the most effective antidotal treatment against acute carbofuran toxicity.

Carbofuran-degrading bacteria from previously treated field soils

Laboratory incubation studies were made on soils collected from five field sites with different histories of treatment with carbofuran. All soils treated earlier with carbofuran degraded the compound more rapidly than untreated samples of the same soils. Reduced rates of degradation in the presence of chloramphenicol imply that soil bacteria are primarily responsible for the breakdown of carbofuran in these soils. Sixty-eight bacteria, capable of degrading carbofuran as the sole source of carbon and nitrogen, were isolated from liquid cultures of treated soils. The concentration of carbofuran in the liquid medium used for isolation and subsequent culture of carbofuran-degrading isolates appeared to affect the stability of their ability to degrade. Similar types of carbofuran-degrading bacteria were isolated from different soils and several different types were isolated from one soil. All carbofuran-degrading isolates were Gram-negative, aerobic rods which hydrolysed the insecticide to carbofuran phenol. They were separated into four groups on the basis of a limited number of phenotypic characters. There was a good correlation between the phenotype of carbofuran-degrading isolates and the stability of their ability to degrade. Fourteen isolates were placed in phenotypic group I and 13 of these did not degrade carbofuran after one subculture in liquid medium. Phenotypic groups II, III and IV consisted of 54 isolates in total (3, 46 and 5 isolates respectively) and 52 of these retained their ability to degrade carbofuran when subcultured.

Toxicity assessment of atrazine, alachlor, and carbofuran and their respective environmental metabolites using Microtox

Using the Microtox method of toxicity assessment designed by Microbics Corporation, the relative toxicities of alachlor, atrazine, and carbofuran, three pesticides commonly used in agricultural production, were determined. Generally, carbofuran was found to be most acutely toxic, followed closely by atrazine. Alachlor was least toxic of the three pesticides tested. Selected environmental metabolites of these three agri-chemicals were also tested using the same method. Hydroxyalachlor, deethylatrazine, deisopropylatrazine, 3-hydroxycarbofuran, and 3-ketocarbofuran were selected for analysis because previous studies determined their presence in surface and ground-water supplies along with their parents. Results showed that often the metabolites were at least as acutely toxic as their parents, particularly in the case of 3-ketocarbofuran and hydroxyalachlor, which demonstrated toxicities higher or not significantly different than their parents. Hydroxycarbofuran was assessed as the least toxic of all substances tested. The atrazine environmental metabolites were less toxic than their parent.

Characterization of a carbofuran-degrading bacterium and investigation of the role of plasmids in catabolism of the insecticide carbofuran

A bacterium capable of using the carbamate insecticide carbofuran as a sole source of carbon and energy, was isolated from soil. The ability to catabolise carbofuran phenol, produced by cleavage of the carbamate ester linkage of the insecticide, was lost at very high frequency when the bacterium was grown in the absence of carbofuran. Plasmid analyses together with curing and mating experiments indicated that the presence of a large plasmid (pIH3, greater than 199 kb) was required for the degradation of carbofuran phenol.

Cloning of a carbofuran hydrolase gene from Achromobacter sp. strain WM111 and its expression in gram-negative bacteria

A 14-kilobase-pair (kbp) EcoRI DNA fragment that encodes an enzyme capable of rapid hydrolysis of N-methylcarbamate insecticides (carbofuran hydrolase) was cloned from carbofuran-degrading Achromobacter sp. strain WM111. When used to probe Southern blots containing plasmid and total DNAs from WM111, this 14-kbp fragment hybridized strongly to a 14-kbp EcoRI fragment from the greater than 100-kbp plasmid harbored by this strain but weakly to EcoRI-digested total DNA from Achromobacter sp. strain WM111, indicating that the gene for N-methylcarbamate degradation (mcd) is plasmid encoded. Further subcloning localized the mcd gene on a 3-kbp ScaI-ClaI fragment. There was little or no expression of this gene in the alternative gram-negative hosts Pseudomonas putida, Alcaligenes eutrophus, Acinetobacter calcoaceticus, and Achromobacter pestifer. Western blotting (immunoblotting) of the protein products produced by low-level expression in P. putida confirmed that this 3-kbp fragment encodes the two 70+-kilodalton protein products seen in sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified carbofuran hydrolase.