Biodegradation of N-methylated carbamates by free and immobilized cells of newly isolated strain Enterobacter cloacae strain TA7

A bacterial strain (TA7) capable of consuming three N-methylated carbamates as sole nitrogen and carbon source was isolated and identified as “Enterobacter cloacae” on the basis of 16S rRNA, from carbamate contaminated agricultural soil by enrichment culture technique. The agar entrapment was used to immobilize the bacterial cells. Both the free as well as the immobilized cells were used to study the degradation of three carbamets viz. aldicarb, carbofuran, and carbaryl. The immobilized cells degraded all the three carbamates much faster than their free cell counterparts. The biodegradation kinetics of aldicarb, carbaryl, and carbofuran was studied using 50 ppm as initial concentration in the presence of free cells. The average values of K_s for aldicarb, carbofuran, and carbaryl were 22.6, 17.87, and 8.9 mg/L, respectively, whereas the values for µ_max were calculated as 1.35, 1.3, and 1.2 mg/l/h^?1. The results indicated that the bacterium has high affinity towards all the three carbamates. However, relatively higher affinity is for carbaryl, in comparison with carbofuran and aldicarb. Results indicate the potential of E. Cloacae TA7 to remediate N-methylated carbamates polluted water and soil.     

Investigation of kinetic interactions between approved oximes and human acetylcholinesterase inhibited by pesticide carbamates

Carbamates are widely used for pest control and act primarily by inhibition of insect and mammalian acetylcholinesterase (AChE). Accidental or intentional uptake of carbamates may result in typical signs and symptoms of cholinergic overstimulation which cannot be discriminated from those of organophosphorus pesticide poisoning. There is an ongoing debate whether standard treatment with atropine and oximes should be recommended for human carbamate poisoning as well, since in vitro and in vivo animal data indicate a deleterious effect of oximes when used in combination with the N-methyl carbamate carbaryl. Therefore, we performed an in vitro kinetic study to investigate the effect of clinically used oximes on carbamoylation and decarbamoylation of human AChE. It became evident that pralidoxime and obidoxime in therapeutic concentrations aggravate the inhibition of AChE by carbaryl and propoxur, with obidoxime being substantially more potent compared to 2-PAM. However, obidoxime had no impact on the decarbamoylation kinetics. Hence, the administration of 2-PAM and especially of obidoxime to severely propoxur and carbaryl poisoned humans cannot be recommended.     

Effect of carbamate esters on neurite outgrowth in differentiating human SK-N-SH neuroblastoma cells

Carbamate esters are widely used as pesticides and can cause neurotoxicity in humans and animals; the exact mechanism is still unclear. In the present investigation, the effects of carbamates at sublethal concentration on neurite outgrowth and cytoskeleton as well as activities of acetylcholinesterase (AChE) and neuropathy target esterase (NTE) in differentiating human SK-N-SH neuroblastoma cells were studied. The results showed that 50 microM of either aldicarb or carbaryl significantly decreased neurite length in the retinoic acid-induced differentiation of the neuroblastoma cells, compared to cells treated with vehicle. Western blot analyses revealed that neither carbamate had significant effects on the levels of actin, or total neurofilament high molecular proteins (NF-H). However, increased NF-H phosphorylation was observed following carbamate treatment. These changes may represent a useful in vitro marker of carbamate neurotoxicity within a simple model of neuronal cell differentiation. Furthermore, activity of AChE, but not NTE, was significantly inhibited by aldicarb and carbaryl in differentiating cells, which suggested that cytoskeletal protein changes induced by carbamate esters in differentiating cells was associated with inhibition of AChE but not NTE.     

Characterization of plasma cholinesterase activity in the Eurasian Griffon Vulture Gyps fulvus and its in vitro inhibition by carbamate pesticides

The legal and illegal use of organophosphorus and carbamate pesticides represents one of many threats to birds. The activity of the cholinesterase enzyme in plasma is used as a non‐destructive biomarker to diagnose the exposure of birds to these pesticides. Scavengers are one of the most important bird groups threatened by the use of baits poisoned with anticholinesterase pesticides. Knowledge of the characteristics of this enzyme in each bird species is crucial, as several studies indicate that more than one cholinesterase form may be present in the plasma of birds. In this study, cholinesterase activity was characterized in the plasma of the Eurasian Griffon Vulture Gyps fulvus by using several substrates and inhibitors of the enzyme, and its normal activity value was also determined. The in vitro sensitivity of Gyps fulvus plasma cholinesterase to carbamate insecticides (aldicarb, carbaryl and methomyl) was also investigated. The results indicated that propionylthiocholine iodide was the preferred substrate to determine plasma cholinesterase activity, followed by acetylcholine iodide and S‐butyrylcholine iodide, and acetylcholinesterase was the predominant enzymatic activity in Gyps fulvus plasma. Aldicarb was the most potent in vitro inhibitor of plasma cholinesterase activity in this species. However, cholinesterase enzymatic activity was significantly inhibited by all tested carbamates, providing further evidence that this biomarker is a suitable tool to monitor the exposure to these poisons in the field, highlighting its utility in conservation programmes.     

Isolation and characterization of fenobucarb-degrading bacteria from rice paddy soils

Forty-five fenobucarb-degrading bacteria were isolated from rice paddy soils, and their genetic and phenotypic characteristics were investigated. The isolates were able to utilize fenobucarb as a sole source of carbon and energy. Analysis of the 16S rRNA gene sequence indicated that all the isolates were related to members of the genera Sphingobium and Novosphingobium. Among 45 isolates, 21 different chromosomal DNA fingerprinting patterns were obtained. All these strains exhibited similar growth and degradation patterns on fenobucarb. 2-sec-butylphenol was identified as an intermediate during fenobucarb degradation by HPLC analysis. All of the isolates were able to degrade another carbamate insecticide, carbaryl, and 2-sec-butylphenol, but not other fenobucarb related compounds such as aldicarb and fenoxycarb. Representative strains of the different repetitive extragenic palindromic sequence PCR fingerprint types had one to six plasmids. The plasmid-cured strains lost their degradation abilities, suggesting that fenobucarb degradative genes were on their plasmid DNAs in these strains. When analyzed with PCR amplification using the primers targeting for the previously reported carbamate hydrolase genes, most of the isolates did not exhibit any positive signals for different genes involved in carbamate degradation such as mcd, cahA and cehA genes. This is the first report that microorganisms involved in the degradation of fenobucarb have been isolated and the intermediate of fenobucarb biodegradation was identified.     

Investigation of salicylanilide and 4-chlorophenol-based N-monosubstituted carbamates as potential inhibitors of acetyl- and butyrylcholinesterase

Based on the presence of carbamate moiety, twenty salicylanilide N-monosubstituted carbamates concomitantly with their parent salicylanilides and five newly prepared 4-chlorophenyl carbamates obtained from isocyanates were investigated using Ellman’s method for their in vitro inhibitory activity against acetylcholinesterase (AChE) from electric eel and butyrylcholinesterase (BChE) from equine serum. The carbamates and salicylanilides exhibited mostly a moderate inhibition of both cholinesterase enzymes with IC₅₀ values ranging from 5 to 235 µM. IC₅₀ values for AChE were in a narrower concentration range when compared to BChE, but many of the compounds produced a balanced inhibition of both cholinesterases. The derivatives were comparable or superior to rivastigmine for AChE inhibition, but only a few of carbamates also for BChE. Several structure-activity relationships were identified, e.g., N-phenethylcarbamates produce clearly favourable BChE inhibition. The compounds also share convenient physicochemical properties for CNS penetration.     

The effect of nitrate and nitrous oxide on hydrogen and methane accumulation in anaerobically-incubated soils

Summary The effect of KNO₃ and N₂O on the accumulation of CH₄, H₂ and denitrification products in two North Dakota soils during anaerobic incubation at 30°C was studied by means of gas chromatography. KNO₃ and N₂O (500 ppm N) reduced the rate of accumulation of CH₄ by a Tetonka soil regardless of whether the soil was in an air-dried condition or had been pre-incubated and actively producing CH₄ prior to the treatment application. Both KNO₃ and N₂O completely suppressed H₂ accumulation by the remoistened air-dried soil; no H₂ either in the presence or absence of added KNO₃ or N₂O was accumulated by the pre-incubated Tetonka soil subsequent to the treatment application. KNO₃ (250 ppm N) reduced the rate of accumulation of CH₄ by a Cavour loam during anaerobic incubation. No H₂ was accumulated by this soil during anaerobic incubation. At equivalent K⁺ concentrations, KNO₃ suppressed CH₄ accumulation by the Tetonka and Cavour soils to a greater extent than did KCl.     

Probing the acyl binding site of acetylcholinesterase by protein engineering

Recombinant acetylcholinesterase from rat brain and two mutants were studied for their hydrolytic activity toward acetyl- and butyrylthiocholine substrates and for their sensitivity toward organophosphate and carbamate inhibitors. Both mutants, a point mutant where F295 was replaced by leucine, and a second mutant where loop PQES was replaced by SG, were designed for increased size of the acyl binding pocket. Wild type and mutant enzymes were expressed in baculovirus-infected insect cells and biochemically characterized. As expected, wild type rat brain acetylcholinesterase hydrolyzed acetylthiocholine, but not butyrylthiocholine. Sensitivity toward small- and medium-sized organophosphate inhibitors like paraoxon-methyl and paraoxon-ethyl was comparable, but bulky organophosphates like ethoprophos were less efficient inhibitors. This tendency applied to carbamates as well, since small carbamoyl moieties like carbofuran and aldicarb were stronger inhibitors than furathiocarb which features a bulky carbamoyl moiety. In contrast to wild type enzyme, both mutants were capable of hydrolyzing butyrylthiocholine. However, k_cat/K_m toward acetylthiocholine of the F295L mutant was reduced if compared to the wild type enzyme. All five organophosphate and three carbamate inhibitors inhibited mutant F295L more efficiently than the wild type enzyme.     

In vivo comparison of N-11CH3 vs O-11CH3 radiolabeled microtubule targeted PET ligands

Altered dynamics of microtubules (MT) are implicated in the pathophysiology of a number of brain diseases. Therefore, radiolabeled MT targeted ligands that can penetrate the blood brain barrier (BBB) may offer a direct and sensitive approach for diagnosis, and assessing the clinical potential of MT targeted therapeutics using PET imaging. We recently reported two BBB penetrating radioligands, [¹¹C]MPC-6827 and [¹¹C]HD-800 as specific PET ligands for imaging MTs in brain. The major metabolic pathway of the above molecules is anticipated to be via the initial labeling site, O-methyl, compared to the N-methyl group. Herein, we report the radiosynthesis of N-¹¹CH₃-MPC-6827 and N-¹¹CH₃-HD-800 and a comparison of their in vivo binding with the corresponding O-¹¹CH₃ analogues using microPET imaging and biodistribution methods. Both O-¹¹CH₃ and N-¹¹CH₃ labeled MT tracers exhibit high specific binding and brain. The N-¹¹CH₃ labeled PET ligands demonstrated similar in vivo binding characteristics compared with the corresponding O-¹¹CH₃ labeled tracers, [¹¹C]MPC-6827 and [¹¹C]HD-800 respectively.     

Difluoromethane, a New and Improved Inhibitor of Methanotrophy

Difluoromethane (HFC-32; DFM) is compared to acetylene and methyl fluoride as an inhibitor of methanotrophy in cultures and soils. DFM was found to be a reversible inhibitor of CH₄ oxidation by Methylococcus capsulatus (Bath). Consumption of CH₄ in soil was blocked by additions of low levels of DFM (0.03 kPa), and this inhibition was reversed by DFM removal. Although a small quantity of DFM was consumed during these incubations, its remaining concentration was sufficiently elevated to sustain inhibition. Methanogenesis in anaerobic soil slurries, including acetoclastic methanogenesis, was unaffected by levels of DFM which inhibit methanotrophy. Low levels of DFM (0.03 kPa) also inhibited nitrification and N₂O production by soils. DFM is proposed as an improved inhibitor of CH₄ oxidation over acetylene and/or methyl fluoride on the basis of its reversibility, its efficacy at low concentrations, its lack of inhibition of methanogenesis, and its low cost.     

A pan‐Arctic synthesis of CH4 and CO2 production from anoxic soil incubations

Permafrost thaw can alter the soil environment through changes in soil moisture, frequently resulting in soil saturation, a shift to anaerobic decomposition, and changes in the plant community. These changes, along with thawing of previously frozen organic material, can alter the form and magnitude of greenhouse gas production from permafrost ecosystems. We synthesized existing methane (CH₄) and carbon dioxide (CO₂) production measurements from anaerobic incubations of boreal and tundra soils from the geographic permafrost region to evaluate large‐scale controls of anaerobic CO₂ and CH₄ production and compare the relative importance of landscape‐level factors (e.g., vegetation type and landscape position), soil properties (e.g., pH, depth, and soil type), and soil environmental conditions (e.g., temperature and relative water table position). We found fivefold higher maximum CH₄ production per gram soil carbon from organic soils than mineral soils. Maximum CH₄ production from soils in the active layer (ground that thaws and refreezes annually) was nearly four times that of permafrost per gram soil carbon, and CH₄ production per gram soil carbon was two times greater from sites without permafrost than sites with permafrost. Maximum CH₄ and median anaerobic CO₂ production decreased with depth, while CO₂:CH₄ production increased with depth. Maximum CH₄ production was highest in soils with herbaceous vegetation and soils that were either consistently or periodically inundated. This synthesis identifies the need to consider biome, landscape position, and vascular/moss vegetation types when modeling CH₄ production in permafrost ecosystems and suggests the need for longer‐term anaerobic incubations to fully capture CH₄ dynamics. Our results demonstrate that as climate warms in arctic and boreal regions, rates of anaerobic CO₂ and CH₄ production will increase, not only as a result of increased temperature, but also from shifts in vegetation and increased ground saturation that will accompany permafrost thaw.     

Select Small Core Structure Carbamates Exhibit High Contact Toxicity to ��Carbamate-Resistant�� Strain Malaria Mosquitoes, Anopheles gambiae (Akron)

Acetylcholinesterase (AChE) is a proven target for control of the malaria mosquito (Anopheles gambiae). Unfortunately, a single amino acid mutation (G119S) in An. gambiae AChE-1 (AgAChE) confers resistance to the AChE inhibitors currently approved by the World Health Organization for indoor residual spraying. In this report, we describe several carbamate inhibitors that potently inhibit G119S AgAChE and that are contact-toxic to carbamate-resistant An. gambiae. PCR-RFLP analysis was used to confirm that carbamate-susceptible G3 and carbamate-resistant Akron strains of An. gambiae carry wild-type (WT) and G119S AChE, respectively. G119S AgAChE was expressed and purified for the first time, and was shown to have only 3% of the turnover number (k _cat) of the WT enzyme. Twelve carbamates were then assayed for inhibition of these enzymes. High resistance ratios (>2,500-fold) were observed for carbamates bearing a benzene ring core, consistent with the carbamate-resistant phenotype of the G119S enzyme. Interestingly, resistance ratios for two oxime methylcarbamates, and for five pyrazol-4-yl methylcarbamates were found to be much lower (4- to 65-fold). The toxicities of these carbamates to live G3 and Akron strain An. gambiae were determined. As expected from the enzyme resistance ratios, carbamates bearing a benzene ring core showed low toxicity to Akron strain An. gambiae (LC₅₀>5,000 μg/mL). However, one oxime methylcarbamate (aldicarb) and five pyrazol-4-yl methylcarbamates (4a–e) showed good to excellent toxicity to the Akron strain (LC₅₀ = 32–650 μg/mL). These results suggest that appropriately functionalized “small-core” carbamates could function as a resistance-breaking anticholinesterase insecticides against the malaria mosquito.     

Effects of Selected Insecticides and Nematicides on the In Vitro Development of the Entomogenous Nematode Neoaplectana carpocapsae

The effects of organophosphates (mevinphos, phenamiphos, trichlorfon), carbamates (carbofuran, methomyl, oxamyl), a formamidine (chlordimeform), a synthetic pyrethroid (fenvalerate), a chlorinated hydrocarbon (methoxychlor). and an insect growth regulator (diflubenzuron) on in vitro development and reproduction of Neoaplectana carflocapsae were tested by incorporating each chemical into a nematode rearing medium. Organophosphates and carbamates adversely affected development and reproduction at concentrations ≥ 0.1 mg/ml. Phenamiphos was the most toxic, with no nematode reproduction at 0.01 mg/ml. Inoculated infective juveniles developed to adults with some of the organophosphates and carbamates, but limited or no reproduction occurred. Chlordimeform inhibited development at 1.0 mg/ml, while diflubenzuron, fenvalerate, and methoxychlor did not significantly (P > 0.05) reduced reproduction at 1.0 mg/ml. The organophosphate and carbamate nematicides in use for control of plant-parasitic nematodes may be toxic to N. carpocapsae in the soil.     

Selective Inhibition of Ammonium Oxidation and Nitrification-Linked N2O Formation by Methyl Fluoride and Dimethyl Ether

Methyl fluoride (CH₃F) and dimethyl ether (DME) inhibited nitrification in washed-cell suspensions of Nitrosomonas europaea and in a variety of oxygenated soils and sediments. Headspace additions of CH₃F (10% [vol/vol]) and DME (25% [vol/vol]) fully inhibited NO₂^- and N₂O production from NH₄⁺ in incubations of N. europaea, while lower concentrations of these gases resulted in partial inhibition. Oxidation of hydroxylamine (NH₂OH) by N. europaea and oxidation of NO₂^- by a Nitrobacter sp. were unaffected by CH₃F or DME. In nitrifying soils, CH₃F and DME inhibited N₂O production. In field experiments with surface flux chambers and intact cores, CH₃F reduced the release of N₂O from soils to the atmosphere by 20- to 30-fold. Inhibition by CH₃F also resulted in decreased NO₃^- + NO₂^- levels and increased NH₄⁺ levels in soils. CH₃F did not affect patterns of dissimilatory nitrate reduction to ammonia in cell suspensions of a nitrate-respiring bacterium, nor did it affect N₂O metabolism in denitrifying soils. CH₃F and DME will be useful in discriminating N₂O production via nitrification and denitrification when both processes occur and in decoupling these processes by blocking NO₂^- and NO₃^- production.     

Susceptibility of an organophosphate resistant strain of the two-spotted spider mite (<Emphasis Type="Italic">Tetranychus urticae</Emphasis>) to mixtures of bifenazate with organophosphate and carbamate insecticides

Bifenazate, a new and frequently used carbazate, is a pro-acaricide which needs to be activated by carboxylesterases. We evaluated the possible antagonism of organophosphate and carbamate insecticides on bifenazate toxicity in Tetranychus urticae applied in mixtures. Two organophosphate resistant strains were used (WI and MR-VL) and several organophosphate (chlorpyrifos, azinphosmethyl and phosmet) and carbamate (carbaryl and methomyl) insecticides were evaluated. Mixing chlorpyrifos with bifenazate decreased bifenazate toxicity in both tested strains. However, in the strain with a higher esterase activity, antagonism decreased after 2 days. Of all other tested chemicals, only methomyl displayed an antagonistic effect 1 day after treatment. These findings indicate that mixing organophosphate and carbamate insecticides with bifenazate may inhibit bifenazate efficacy under field conditions, especially when resistant strains are present.     

Effect of baygon (2-isopropoxyphenyl N-methylcarbamate) on some soil biological processes and its degradation by a Pseudomonas sp.

Summary Baygon (2-isopropoxyphenyl-N-methylcarbamate) inhibited nitrification for 4 weeks at 25 and for 16 weeks at 1250 ppm. Ammonification of peptone was stimulated by baygon. Oxidation of ammonium formed from peptone was not complete in 16 weeks at 1250 ppm. of baygon. Solubilization of tricalcium phosphate was not affected by baygon. CO₂ production from soil was depressed for 10 days. Glucose addition caused the higher depression of CO₂ production after a week. A Pseudomonas sp. degraded baygon to 2-isopropoxyphenol. re]19730507     

Synthesis and characterization of new inhibitors of cholinesterases based on N-phenylcarbamates: In vitro study of inhibitory effect,type of inhibition,lipophilicity and molecular docking

Based on current treatment of Alzheimer's disease, where the carbamate inhibitor Rivastigmine is used, two series of carbamate derivatives were prepared: (i) N-phenylcarbamates with additional carbamate group (1–12) and (ii) N-phenylcarbamates with monosaccharide moiety (13–24). All compounds were tested for the inhibitory effect on both of the cholinesterases, electric eel acetylcholinesterase (eeAChE) and butyrylcholinesterase from equine serum (eqBChE) and the inhibitory activity (expressed as IC₅₀ values) was compared with that of the established drugs Galanthamine and Rivastigmine. The compounds with two carbamate groups 1–12 revealed higher inhibitory efficiency on both cholinesterases in compared with monosaccharide derived carbamates 13–24 and with Rivastigmine. The significant decrease of inhibitory efficiency on eqBChE (also for eeAChE but in less manner) was observed after deacetalization of monosaccharide. Moreover, the type of inhibitory mechanism of five chosen compounds was studied. It was found, that compounds with two carbamate groups act presumably via a mixed inhibitory mechanism and the compounds with monosaccharide moiety act as non-competitive inhibitors. The lipophilicity of tested compounds was determined using partition coefficient. Specific positions of the inhibitors in the binding sites of cholinesterases were determined using molecular modeling and the results indicate the importance of phenylcarbamate orientation in the catalytic gorges of both enzymes.     

Nitrous Oxide Production and Methane Oxidation by Different Ammonia-Oxidizing Bacteria

Ammonia-oxidizing bacteria (AOB) are thought to contribute significantly to N₂O production and methane oxidation in soils. Most of our knowledge derives from experiments with Nitrosomonas europaea, which appears to be of minor importance in most soils compared to Nitrosospira spp. We have conducted a comparative study of levels of aerobic N₂O production in six phylogenetically different Nitrosospira strains newly isolated from soils and in two N. europaea and Nitrosospira multiformis type strains. The fraction of oxidized ammonium released as N₂O during aerobic growth was remarkably constant (0.07 to 0.1%) for all the Nitrosospira strains, irrespective of the substrate supply (urea versus ammonium), the pH, or substrate limitation. N. europaea and Nitrosospira multiformis released similar fractions of N₂O when they were supplied with ample amounts of substrates, but the fractions rose sharply (to 1 to 5%) when they were restricted by a low pH or substrate limitation. Phosphate buffer (versus HEPES) doubled the N₂O release for all types of AOB. No detectable oxidation of atmospheric methane was detected. Calculations based on detection limits as well as data in the literature on CH₄ oxidation by AOB bacteria prove that none of the tested strains contribute significantly to the oxidation of atmospheric CH₄ in soils.     

The interaction of carbon-14-labelled alkyl carbamates, labelled in the alkyl and carbonyl positions, with DNA in vivo

The binding of ethyl carbamate labelled with carbon-14 in the alkyl or carbonyl group, and of methyl, n-butyl and n-propyl carbamates labelled in the alkyl group, to the DNA of mouse liver, lung and kidney has been studied in male Crackenbush mice. Only ethyl carbamate bound to liver and kidney DNA to any significant extent.The binding of ethyl carbamate labelled with carbon-14 in the C₁, C₂ or the carbonyl position was examined and compared. The levels of binding of [1-¹⁴C]- and [2-¹⁴C]ethyl carbamate to liver DNA were not significantly different (328 ± 34 and 267 ± 24 dpm/mg DNA, respectively), but there was very little binding of the [carbonyl-¹⁴C]ethyl carbamate (26 ± 3 dpm/mg DNA). Furthermore, only 18% of the radioactivity was removed from the DNA labelled with the alkyl-labelled carbamates, whereas 65% of the radioactivity was removed from the DNA labelled with carbonyl-labelled ethyl carbamate on continuous ether extraction. It was concluded that the bound molecule does not contain the carbonyl carbon and is probably an ethyl group.     

Efficacy of Aldicarb to Rotylenchulus reniformis and Biodegradation in Cotton Field Soils

The microbial degradation of aldicarb was examined in the greenhouse using soil from four cotton fields with a history of aldicarb use. The addition of aldicarb at 0.59 kg a.i./ha to natural soil increased Rotylenchulus reniformis numbers 6.6% in one soil and decreased R. reniformis numbers only 25.8% in another soil as compared to the corresponding natural soil without aldicarb. The use of increasing rates of aldicarb did not increase the efficacy of aldicarb in these soils. Rotylenchulus reniformis numbers were reduced 39.8, 22.6, and 6.8%, and increased 5.7% for aldicarb applied at 0.29, 0.59, 0.85, and 1.19 kg a.i./ha, respectively, in one natural soil. In another natural soil, R. reniformis numbers were reduced 42.5 and 21.9% for aldicarb applied at 0.29 and 1.19 kg a.i./ha, respectively, but increased 19.1 and 10.6% for aldicarb applied at 0.59 and 0.85 kg a.i./ha, respectively. Autoclaving the soils restored aldicarb toxicity in both soils, and R. reniformis numbers were reduced 96 and 99%, respectively, as compared to autoclaved soil without aldicarb. Bacterial populations were greater in the natural soils where aldicarb did not reduce R. reniformis numbers relative to the same soils that were autoclaved. However, no bacterial species was consistently associated with aldicarb degradation.