Effect of bioaugmentation and supplementary carbon sources on degradation of polycyclic aromatic hydrocarbons by a soil-derived culture

The degradation of polycyclic aromatic hydrocarbons (PAHs) by an undefined culture obtained from a PAH-polluted soil and the same culture bioaugmented with three PAH-degrading strains was studied in carbon-limited chemostat cultures. The PAHs were degraded efficiently by the soil culture and bioaugmentation did not significantly improve the PAH degrading performance. The presence of PAHs did, however, influence the bacterial composition of the bioaugmented and non-bioaugmented soil cultures, resulting in the increase in cell concentration of sphingomonad strains. the initial enhancement of the degradation of the PAHs by biostimulation gradually disappeared and only the presence of salicylate in the additional carbon sources had a lasting slightly stimulating effect on the degradation of phenanthrene. The results suggest that bioaugmentation and biostimulation have limited potential to enhance PAH bioremediation by culture already proficient in the degradation of such contaminants.     

Substrate interactions of benzene, toluene, and para-xylene during microbial degradation by pure cultures and mixed culture aquifer slurries.

Benzene, toluene, and p-xylene (BTX) were degraded by indigenous mixed cultures in sandy aquifer material and by two pure cultures isolated from the same site. Although BTX compounds have a similar chemical structure, the fate of individual BTX compounds differed when the compounds were fed to each pure culture and mixed culture aquifer slurries. The identification of substrate interactions aided the understanding of this behavior. Beneficial substrate interactions included enhanced degradation of benzene and p-xylene by the presence of toluene in Pseudomonas sp. strain CFS-215 incubations, as well as benzene-dependent degradation of toluene and p-xylene by Arthrobacter sp. strain HCB. Detrimental substrate interactions included retardation in benzene and toluene degradation by the presence of p-xylene in both aquifer slurries and Pseudomonas incubations. The catabolic diversity of microbes in the environment precludes generalizations about the capacity of individual BTX compounds to enhance or inhibit the degradation of other BTX compounds.     

Degradation of phenanthrene,fluorene and fluoranthene by pure bacterial cultures

Summary Bacterial mixed cultures able to degrade the polycyclic aromatic hydrocarbons (PAH) phenanthrene, fluorene and fluoranthene, were obtained from soil using conventional enrichment techniques. From these mixed cultures three pure strains were isolated:Pseudomonas paucimobilis degrading phenanthrene;P. vesicularis degrading fluorene andAlcaligenes denitrificans degrading fluoranthene. The maximum rates of PAH degradation ranged from 1.0 mg phenanthrene/ml per day to 0.3 mg fluoranthene/ml per day at doubling times of 12 h to 35 h for growth on PAH as sole carbon source. The protein yield during PAH degradation was about 0.25 mg/mg C for all strains. Maximum PAH oxidation rates and optimum specific bacterial growth were obtained near pH 7.0 and 30°C. After growth entered the stationary phase, no dead end-products of PAH degradation could be detected in the culture fluid.     

Total biodegradation of the oestrogenic mycotoxin zearalenone by a bacterial culture

A mixed culture of bacteria, enriched from soil collected at a coal gasification site, proved capable of removing the potent oestrogenic mycotoxin zearalenone from culture media. The bacteria grew rapidly when zearalenone was provided as the sole source of carbon and energy. HPLC and ELISA analysis of culture extracts revealed no zearalenone or zearalenone-like products. Fourteen bacterial isolates from the mixed culture were identified and purified. The ability to degrade zearalenone was lost upon purification and recombination of the bacterial members of the mixed culture. A strain of Pseudomonas fluorescens capable of degrading polychlorinated biphenyls was unable to degrade zearalenone. This is the first report of the complete degradation of zearalenone by bacteria. The present study suggests the potential of mixed cultures in the biodegradation of zearalenone.     

Comparison of autochthonous bacteria and commercially available cultures with respect to their effectiveness in fuel oil degradation

Summary This study examined the microbial degradation of fuel oil by nine highly adapted different commercially available mixed bacterial cultures (DBC-plus, Flow Laboratories, Meckenheim, F.R.G.) and a bacterial community from a domestic sewage sludge sample. All mixed cultures were cultivated under aerobic batch conditions shaking (110 rpm) at 20°C in a mineral base medium containing 1 or 5% (v/v) fuel oil as the sole carbon source. Percent degradation of fuel oil and the n-alkane fraction was recorded for the nine DBC-plus cultures and the mixed population of the activated sludge sample. The increase in colony counts, protein, and optical density was studied during a 31-day incubation period for DBC-plus culture A, DBC-plus culture A2 and the activated sludge sample. The activated sludge mixed culture was most effective in degrading fuel oil, but various isolated bacterial strains from this bacterial community were not able to grow on fuel oil as the sole carbon source. In contrast, the n-alkane degradation rates of the DBC-cultures were lower, but single strains from the commercially available mixed cultures were able to mineralize fuel oil hydrocarbons. Strains ofPseudomonas aeruginosa were isolated most frequently and these organisms were able to grow very rapidly on fuel oil as a complex sole carbon source. The results indicate that fuel oil degradation in domestic sewage sludge is performed by mixed populations of naturally occurring bacteria and does not depend on the application of highly adapted commercially available cultures.     

Role of soil pH in the development of enhanced biodegradation of fenamiphos

Repeated treatment with fenamiphos (ethyl 4-methylthio-m-tolyl isopropylphosphoramidate) resulted in enhanced biodegradation of this nematicide in two United Kingdom soils with a high pH (>/= 7.7). In contrast, degradation of fenamiphos was slow in three acidic United Kingdom soils (pH 4.7 to 6.7), and repeated treatments did not result in enhanced biodegradation. Rapid degradation of fenamiphos was observed in two Australian soils (pH 6.7 to 6.8) in which it was no longer biologically active against plant nematodes. Enhanced degrading capability was readily transferred from Australian soil to United Kingdom soils, but only those with a high pH were able to maintain this capability for extended periods of time. This result was confirmed by fingerprinting bacterial communities by 16S rRNA gene profiling of extracted DNA. Only United Kingdom soils with a high pH retained bacterial DNA bands originating from the fenamiphos-degrading Australian soil. A degrading consortium was enriched from the Australian soil that utilized fenamiphos as a sole source of carbon. The 16S rRNA banding pattern (determined by denaturing gradient gel electrophoresis) from the isolated consortium migrated to the same position as the bands from the Australian soil and those from the enhanced United Kingdom soils in which the Australian soil had been added. When the bands from the consortium and the soil were sequenced and compared they showed between 97 and 100% sequence identity, confirming that these groups of bacteria were involved in degrading fenamiphos in the soils. The sequences obtained showed similarity to those from the genera Pseudomonas, Flavobacterium, and CAULOBACTER: In the Australian soils, two different degradative pathways operated simultaneously: fenamiphos was converted to fenamiphos sulfoxide (FSO), which was hydrolyzed to the corresponding phenol (FSO-OH) or was hydrolyzed directly to fenamiphos phenol. In the United Kingdom soils in which enhanced degradation had been induced, fenamiphos was oxidized to FSO and then hydrolyzed to FSO-OH, but direct conversion to fenamiphos phenol did not occur.     

除草剂二甲戊灵的真菌降解及其特性研究

富集分离了除草剂二甲戊灵降解真菌,并研究了其降解特性,结果表明,真菌可以降解二甲戊灵,利用富集培养的方法从环境中分离到16株能降解二甲戊灵的真菌。其中10株真菌5d内对100mg·L^-1二甲戊灵的降解率大于60％,以其中3株生理耐受能力强、降解能力高的真菌为例,研究了外加碳源浓度、初始pH值、二甲戊灵浓度和培养温度对真菌生长量和降解能力的影响,此3株真菌经鉴定分别属于土生曲霉组(Aspergillus terreus)、长梗串孢霉属(Monilochaetes)和烟色曲霉组(Aspergillus furnigatus),在外加碳源浓度为0．5％～1．0％的范围内,真菌生长量和降解率达到最大;在中性培养液中,3株真菌的生长量大,降解能力强;在浓度为100mg·L^-1时降解率和生长量都比较大,而绝对去除量随二甲戊灵浓度的提高而增加,在500mg·L^-1时达到最大;真菌的生长和降解需要适宜的温度,20～30℃培养时,降解率和生长量最大,可为农药污染治理及生产污水处理提供理论依据。     

Role of Soil pH in the Development of Enhanced Biodegradation of Fenamiphos

Repeated treatment with fenamiphos (ethyl 4-methylthio-m-tolyl isopropylphosphoramidate) resulted in enhanced biodegradation of this nematicide in two United Kingdom soils with a high pH (≥7.7). In contrast, degradation of fenamiphos was slow in three acidic United Kingdom soils (pH 4.7 to 6.7), and repeated treatments did not result in enhanced biodegradation. Rapid degradation of fenamiphos was observed in two Australian soils (pH 6.7 to 6.8) in which it was no longer biologically active against plant nematodes. Enhanced degrading capability was readily transferred from Australian soil to United Kingdom soils, but only those with a high pH were able to maintain this capability for extended periods of time. This result was confirmed by fingerprinting bacterial communities by 16S rRNA gene profiling of extracted DNA. Only United Kingdom soils with a high pH retained bacterial DNA bands originating from the fenamiphos-degrading Australian soil. A degrading consortium was enriched from the Australian soil that utilized fenamiphos as a sole source of carbon. The 16S rRNA banding pattern (determined by denaturing gradient gel electrophoresis) from the isolated consortium migrated to the same position as the bands from the Australian soil and those from the enhanced United Kingdom soils in which the Australian soil had been added. When the bands from the consortium and the soil were sequenced and compared they showed between 97 and 100% sequence identity, confirming that these groups of bacteria were involved in degrading fenamiphos in the soils. The sequences obtained showed similarity to those from the genera Pseudomonas, Flavobacterium, and Caulobacter. In the Australian soils, two different degradative pathways operated simultaneously: fenamiphos was converted to fenamiphos sulfoxide (FSO), which was hydrolyzed to the corresponding phenol (FSO-OH) or was hydrolyzed directly to fenamiphos phenol. In the United Kingdom soils in which enhanced degradation had been induced, fenamiphos was oxidized to FSO and then hydrolyzed to FSO-OH, but direct conversion to fenamiphos phenol did not occur.     

Characterization of the biodegradation,bioremediation and detoxification capacity of a bacterial consortium able to degrade the fungicide thiabendazole

Thiabendazole (TBZ) is a persistent fungicide used in the post-harvest treatment of fruits. Its application results in the production of contaminated effluents which should be treated before their environmental discharge. In the absence of efficient treatment methods in place, biological systems based on microbial inocula with specialized degrading capacities against TBZ could be a feasible treatment approach. Only recently the first bacterial consortium able to rapidly transform TBZ was isolated. This study aimed to characterize its biodegradation, bioremediation and detoxification potential. The capacity of the consortium to mineralize ¹⁴C-benzyl-ring labelled TBZ was initially assessed. Subsequent tests evaluated its degradation capacity under various conditions (range of pH, temperatures and TBZ concentration levels) and relevant practical scenarios (simultaneous presence of other postharvest compounds) and its bioaugmentation potential in soils contaminated with increasing TBZ levels. Finally cytotoxicity assays explored its detoxification potential. The consortium effectively mineralized the benzoyl ring of the benzimidazole moiety of TBZ and degraded spillage level concentrations of the fungicide in aqueous cultures (750 mg L^?1) and in soil (500 mg kg^?1). It maintained its high degradation capacity in a wide range of pH (4.5–7.5) and temperatures (15–37 °C) and in the presence of other pesticides (ortho-phenylphenol and diphenylamine). Toxicity assays using the human liver cancer cell line HepG2 showed a progressive decrease in cytotoxicity, concomitantly with the biodegradation of TBZ, pointing to a detoxification process. Overall, the bacterial consortium showed high potential for future implementation in bioremediation and biodepuration applications.     

A novel pathway for mineralization of the thiocarbamate herbicide molinate by a defined bacterial mixed culture

A bacterial mixed culture able to mineralize molinate was established, through enrichment, using mineral medium with molinate as the only carbon, nitrogen and energy source. The combination of five cultivable isolates, purified from the enrichment culture, permitted the reconstitution of a degrading consortium. Both enrichment and defined cultures were able to mineralize molinate without accumulation of degradation products by the end of the growth. Among the five isolates constituting the defined mixed culture, an actinomycete, strain ON4, was essential for biodegradation, being involved in the cleavage of the thioester bond of molinate, the initial step of the degradation pathway. Isolate ON4 was able to grow on molinate at concentrations below 2 mM, with the accumulation of ethanethiol and diethyl disulphide. These sulphur compounds were toxic to strain ON4 when accumulating at higher concentrations. However, this inhibitory effect was avoided by the presence of other members of the mixed culture, out of which isolates ON1 and ON2 were observed to consume ethanethiol and diethyl disulphide. In this way, interactions among defined mixed culture members involve metabolic and detoxifying association.     

Bacterial breakdown of benomyl. II. Mixed cultures

Experiments with mixed bacterial cultures grown in liquid media which contained the benzimidazole fungicide benomyl, with or without Na-lactate, as source of carbon provided circumstantial evidence for cleavage of the benzimidazole heterocyclic ring. Yet, neither 2-aminobenzimidazole (2-AB) nor benzimidazole, as sole source of carbon, supported any bacterial growth. Total ¹⁴C-balance analysis experiments conclusively showed production of ¹⁴CO₂ from [2-¹⁴C] methyl benzimidazol-2-yl carbamate (MBC), and thus cleavage of the benzimidazole nucleus; bioassays, however, showed that the actual rate of benomyl and MBC breakdown was only small, the parent compound benomyl being still recovered in substantial quantities after up to 80 days of incubation. Therefore, cleavage of the benzimidazole ring is probably a matter of cometabolism, n-butylamine which originates from the butylcarbamoyl side chain serving as the proper source of carbon.Besides radiolabelled 2-AB and CO₂, an unknown metabolite was isolated which showed characteristics of a 2-AB-nucleotide. Probably, 2-AB was incorporated into bacterial DNA, which upon lysis of the bacterial cells gave rise to the nucleotide in question. Therefore, 2-AB might exert its inhibitory action by interfering with the normal functioning of DNA.     

Substrate interactions of benzene, toluene, and para-xylene during microbial degradation by pure cultures and mixed culture aquifer slurries.

Benzene, toluene, and p-xylene (BTX) were degraded by indigenous mixed cultures in sandy aquifer material and by two pure cultures isolated from the same site. Although BTX compounds have a similar chemical structure, the fate of individual BTX compounds differed when the compounds were fed to each pure culture and mixed culture aquifer slurries. The identification of substrate interactions aided the understanding of this behavior. Beneficial substrate interactions included enhanced degradation of benzene and p-xylene by the presence of toluene in Pseudomonas sp. strain CFS-215 incubations, as well as benzene-dependent degradation of toluene and p-xylene by Arthrobacter sp. strain HCB. Detrimental substrate interactions included retardation in benzene and toluene degradation by the presence of p-xylene in both aquifer slurries and Pseudomonas incubations. The catabolic diversity of microbes in the environment precludes generalizations about the capacity of individual BTX compounds to enhance or inhibit the degradation of other BTX compounds.     

基于吐温-80下2株功能菌协同降解多环芳烃的特性研究

【目的】研究恶臭假单胞菌B6-2和克雷伯氏菌CW-D3T构建的混合功能菌对多环芳烃的协同修复效能,并探究非离子表面活性剂吐温-80对混菌降解多环芳烃的影响,以期为芳烃化合物的生物修复提供技术参考和理论依据。【方法】通过生长曲线及平板菌落计数法反映混菌生长情况及比例,从而评估混菌降解体系的可行性;通过高效液相色谱法探究各体系以及不同吐温-80浓度下混培体系对多环芳烃的降解效能;最后通过烷烃吸附法测定细胞表面疏水性,以探究吐温-80对混合功能菌降解多环芳烃的影响机制。【结果】等比例混合的2株菌共培养生长状态优于纯培体系,对混合多环芳烃(菲、荧蒽、芘)的降解率分别为33.4%、30.1%、28.6%(7 d),相较于菌CW-D3T,分别提高了1.31倍、1.46倍、1.42倍。混培体系中加入500 mg/L的吐温-80对菲、荧蒽、芘的降解率分别为47.7%、43.2%、38.8%(7 d),相较于对照组各提高了1.55倍、1.38倍、1.31倍,而更高浓度的吐温-80无明显促进作用或轻微抑制。添加吐温-80使菌CW-D3T和混菌的表面疏水性提高,而菌B6-2表面疏水性降低。结合细菌生长量分析...     

Enrichment of mixed cultures capable of aerobic degradation of 1,2-dibromoethane.

1,2-dibromoethane (DBE) is a common environmental contaminant; it is potentially carcinogenic and has been detected in soil and groundwater supplies. Most of the biodegradation studies to date have been performed under anaerobic conditions or in the context of soil remediation, where the pollutant concentration was in the parts per billion range. In this work a mixed bacterial culture capable of complete aerobic mineralization of concentrations of DBE up to 1 g liter(-1) under well-controlled laboratory conditions was enriched. In order to verify biodegradation, formation of biodegradation products as well as the disappearance of DBE from the biological medium were measured. Complete mineralization was verified by measuring stoichiometric release of the biodegradation products. This mixed culture was found to be capable of degrading other halogenated compounds, including bromoethanol, the degradation of which has not been reported previously.     

Bacterial decolorization of black liquor in axenic and mixed condition and characterization of metabolites

The pulping byproducts (black liquor) cause serious environmental problem due to its high pollution load. In order to search the degradability of black liquor, the potential bacterial strains Citrobacter freundii (FJ581026) and Citrobacter sp. (FJ581023) were applied in axenic and mixed condition. Results revealed that the mixed bacterial culture are more effective than axenic condition and can reduce 82% COD, 79% AOX, 79% color and 60% lignin after 144 h of incubation period. Additionally, the optimum activity of lignin degrading enzyme was noted at 96 h and characterized as manganese peroxidase (MnP) by SDS–PAGE analysis. Further, the HPLC analysis of control and bacterial degraded sample has shown the reduction as well as shifting of peaks compared to control indicating the degradation as well as transformation of compounds of black liquor. The comparative GC–MS analysis of control and degraded black liquor revealed that along with lignin fragment some chlorophenolic compounds 2,4,6-trichlorophenol, 2,3,4,5-tetrachlorophenol and pentachlorophenol were detected in black liquor degraded by axenic culture whereas these chlorophenolic compounds were completely absent in black liquor degraded by mixed bacterial culture. These chlorophenol inhibit the oxidative degradation which seems a major reason behind the low degradability of axenic degradation compared to mixed culture. The innovation of this aerobic treatment of alkaline black liquor opens additional possibilities for the better treatment of black liquor along with its metabolic product.     

Towards efficient crude oil degradation by a mixed bacterial consortium

A laboratory study was undertaken to assess the optimal conditions for biodegradation of Bombay High (BH) crude oil. Among 130 oil degrading bacterial cultures isolated from oil contaminated soil samples, Micrococcus sp. GS2-22, Corynebacterium sp. GS5-66, Flavobacterium sp. DS5-73, Bacillus sp. DS6-86 and Pseudomonas sp. DS10-129 were selected for the study based on the efficiency of crude oil utilisation. A mixed bacterial consortium prepared using the above strains was also used. Individual bacterial cultures showed less growth and degradation than did the mixed bacterial consortium. At 1% crude oil concentration, the mixed bacterial consortium degraded a maximum of 78% of BH crude oil. This was followed by 66% by Pseudomonas sp. DS10-129, 59% by Bacillus sp. DS6-86, 49% by Micrococcus sp. GS2-22, 43% by Corynebacterium sp. GS5-66 and 41% by Flavobacterium sp. DS5-73. The percentage of degradation by the mixed bacterial consortium decreased from 78% to 52% as the concentration of crude oil was increased from 1% to 10%. Temperature of 30 degrees C and pH 7.5 were found to be optima for maximum biodegradation.     

Fungi are the predominant micro-organisms responsible for degradation of soil-buried polyester polyurethane over a range of soil water holding capacities

AIMS: To investigate the relationship between soil water holding capacity (WHC) and biodegradation of polyester polyurethane (PU) and to quantify and identify the predominant degrading micro-organisms in the biofilms on plastic buried in soil. METHODS AND RESULTS: High numbers of both fungi and bacteria were recovered from biofilms on soil-buried dumb-bell-shaped pieces of polyester PU after 44 days at 15-100% WHC. The tensile strength of the polyester PU was reduced by up to 60% over 20-80% soil WHC, but no reduction occurred at 15, 90 or 100% soil WHC. A PU agar clearance assay indicated that fungi, but not bacteria were, the major degrading organisms in the biofilms on polyester PU and 10-30% of all the isolated fungi were able to degrade polyester PU in this assay. A 5.8S rDNA sequencing identified 13 strains of fungi representing the three major colony morphology types responsible for PU degradation. Sequence homology matches identified these strains as Nectria gliocladioides (five strains), Penicillium ochrochloron (one strain) and Geomyces pannorum (seven strains). Geomyces pannorum was the predominant organism in the biofilms comprising 22-100% of the viable polyester PU degrading fungi. CONCLUSIONS: Polyester PU degradation was optimum under a wide range of soil WHC and the predominant degrading organisms were fungi. SIGNIFICANCE AND IMPACT OF THE STUDY: By identifying the predominant degrading fungi in soil and studying the optimum WHC conditions for degradation of PU it allows us to better understand how plastics are broken down in the environment such as in landfill sites.     

Effects of soil pH on the biodegradation of chlorpyrifos and isolation of a chlorpyrifos-degrading bacterium

We examined the role of microorganisms in the degradation of the organophosphate insecticide chlorpyrifos in soils from the United Kingdom and Australia. The kinetics of degradation in five United Kingdom soils varying in pH from 4.7 to 8.4 suggested that dissipation of chlorpyrifos was mediated by the cometabolic activities of the soil microorganisms. Repeated application of chlorpyrifos to these soils did not result in the development of a microbial population with an enhanced ability to degrade the pesticide. A robust bacterial population that utilized chlorpyrifos as a source of carbon was detected in an Australian soil. The enhanced ability to degrade chlorpyrifos in the Australian soil was successfully transferred to the five United Kingdom soils. Only soils with a pH of >/=6.7 were able to maintain this degrading ability 90 days after inoculation. Transfer and proliferation of degrading microorganisms from the Australian soil to the United Kingdom soils was monitored by molecular fingerprinting of bacterial 16S rRNA genes by PCR-denaturing gradient gel electrophoresis (DGGE). Two bands were found to be associated with enhanced degradation of chlorpyrifos. Band 1 had sequence similarity to enterics and their relatives, while band 2 had sequence similarity to strains of Pseudomonas. Liquid enrichment culture using the Australian soil as the source of the inoculum led to the isolation of a chlorpyrifos-degrading bacterium. This strain had a 16S rRNA gene with a sequence identical to that of band 1 in the DGGE profile of the Australian soil. DNA probing indicated that genes similar to known organophosphate-degrading (opd) genes were present in the United Kingdom soils. However, no DNA hybridization signal was detected for the Australian soil or the isolated degrader. This indicates that unrelated genes were present in both the Australian soil and the chlorpyrifos-degrading isolate. These results are consistent with our observations that degradation of chlorpyrifos in these systems was unusual, as it was growth linked and involved complete mineralization. As the 16S rRNA gene of the isolate matched a visible DGGE band from the Australian soil, the isolate is likely to be both prominent and involved in the degradation of chlorpyrifos in this soil.     

Degradation of fluoranthene in a soil matrix by indigenous and introduced bacteria

Microbial growth and degradation of fluoranthene in amended soil microcosms by the indigenous microbial population and a PAH degrading mixed culture inoculum were characterised. Percentages of fluoranthene disappearance ranged from 14.4 % in sterilised uninoculated soil microcosms to 52.1 % in unsterilized inoculated microcosms. Inoculated soils had initial microbial counts approximately one order of magnitude higher than the indigenous soil count and exhibited enhanced fluoranthene degradation. Over a nine week incubation period, total viable counts in inoculated non-sterile soil declined to the levels observed for the original indigenous population.     

Biodegradation of the Phenylurea Herbicide Isoproturon and its Metabolites in Agricultural Soils

Degradation of the phenylurea herbicide isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea) and several phenylurea and aniline metabolites was studied in agricultural soils previously exposed to isoproturon. The potential for degradation of the demethylated metabolite 3-(4-isopropylphenyl)-1-methylurea in the soils was much higher compared to isoproturon. In the most active soil only 6% of added ¹⁴C-labelled isoproturon was mineralised to ¹⁴C₂ within 20 days while in the same period 45% of added ¹⁴C-labelled 3-(4-isopropylphenyl)-1-methylurea was mineralized. This indicates that the initial N-demethylation may be a limiting step in the complete mineralization of isoproturon. Repeated addition of 3-(4-isopropylphenyl)-1-methylurea to the soil and further subculturing in mineral medium led to a highly enriched mixed bacterial culture with the ability to mineralize 3-(4-isopropylphenyl)-1-methylurea.The culture did not degrade either isoproturon or the didemethylatedmetabolite 3-(4-isopropylphenyl)-urea when provided as sole source of carbon and energy. The metabolite 4-isopropyl-aniline was also degraded and utilised for growth, thus indicating that 3-(4-isopropylphenyl)-1-methylurea is degraded byan initial cleavage of the methylurea-group followed by mineralizationof the phenyl-moiety. Several attempts were made to isolate pure bacterial cultures degrading 3-(4-isopropylphenyl)-1-methylurea or 4-isopropyl-aniline,but they were not successful.