Biodegradation of Swainsonine by Acinetobacter calcoaceticus strain YLZZ-1 and its isolation and identification

Eight swainsonine (SW)-degrading bacteria were isolated from the soil where locoweed was buried for 6 months and one of the strains (YLZZ-1) was selected for further study. Based on morphology, physiologic tests, 16S rRNA gene sequence, and phylogenetic characteristics, the strain showed the greatest similarity to members of the order Acinetobacters and within the order to members of the Acinetobacter calcoaceticus group. The ability of the strain for degrading SW, as sole carbon source, was investigated under different culture conditions. The preferential temperature and initial pH for the strain were 25–35°C and 6–9, respectively. The optimal temperature for the strain was 30°C and the optimal pH was 7.0. There was a positive correlation between degradation rate and inoculation amount. The concentration of SW affected the degradation ability. When the concentration of SW was lower than 100 mg/l, SW decreased immediately after incubation, and when the concentration of SW was 200 mg/l, there was an inhibiting effect for bacteria growth and SW degradation. The strain could degrade SW completely within 14 h when the concentration of SW was 50 mg/l. These results highlight the potential of this bacterium to be used in detoxifying of SW in livestock consuming locoweed.     

Biodegradation of pyrazosulfuron-ethyl by <Emphasis Type="Italic">Acinetobacter</Emphasis> sp. CW17

The pyrazosulfuron-ethyl-degrading bacterium, designated as CW17, was isolated from contaminated soil near the warehouse of the factory producing pyrazosulfuron-ethyl in Changsha city, China. The strain CW17 was identified as Acinetobacter sp. based on analyses of 94 carbon source utilization or chemical sensitivity in Biolog microplates, conventional phenotypic characteristics, and 16S rRNA gene sequencing. When pyrazosulfuron-ethyl was provided as the sole carbon source, the effects of pyrazosulfuron-ethyl concentration, pH, and temperature on biodegradation were examined. The degradation rates of pyrazosulfuron-ethyl at initial concentrations of 5.0, 20.0, and 50.0 mg/L were 48.0%, 77.0%, and 32.6%, respectively, after inoculation for 7 days. The growth of the strain was inhibited at low pH buffers. The chemical degradation occurs much faster at low pH than at neutral and basic pH conditions. The degradation rate of pyrazosulfuron-ethyl at 30°C was faster than those at 20 and 37°C by CW17 strains. Two metabolites of degradation were analyzed by liquid chromatography–mass spectroscopy (LC/MS). Based on the identified products, strain CW17 seemed to be able to degrade pyrazosulfuron-ethyl by cleavage of the sulfonylurea bridge.     

Characterization of Fluoroglycofen Ethyl Degradation by Strain <Emphasis Type="Italic">Mycobacterium phocaicum</Emphasis> MBWY-1

A fluoroglycofen ethyl-degrading bacterium, MBWY-1, was isolated from the soil of an herbicide factory. This isolated strain was identified as Mycobacterium phocaicum based on analysis of its 16S rRNA gene sequence and its morphological, physiological, and biochemical properties. The strain was able to utilize fluoroglycofen ethyl as its sole source of carbon for growth and could degrade 100 mg l⁻¹ of fluoroglycofen ethyl to a non-detectable level within 72 h. The optimum temperature and pH for fluoroglycofen ethyl degradation by strain MBWY-1 were 30°C and 7.0, respectively. Five metabolites produced during the degradation of fluoroglycofen ethyl and were identified by mass spectrometry as {5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrophenylacyl} hydroxyacetic acid, acifluorfen, 5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoate, 5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-hydroxyl, and 3-chloro-4-hydroxyl benzotrifluoride. Identification of the metabolites allowed to propose the degradation pathway of fluoroglycofen ethyl by strain MBWY-1. The inoculation of strain MBWY-1 into soil treated with fluoroglycofen ethyl resulted in a higher fluoroglycofen ethyl degradation rate than in uninoculated soil regardless of whether the soil was sterilized or nonsterilized.     

Role of eukaryotic microbiota in soil survival and catabolic performance of the 2,4-D herbicide degrading bacteria <Emphasis Type="Italic">Cupriavidus necator</Emphasis> JMP134

Cupriavidus necator (formerly Ralstonia eutropha) JMP134, harbouring the catabolic plasmid pJP4, is the best-studied 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide degrading bacterium. A study of the survival and catabolic performance of strain JMP134 in agricultural soil microcosms exposed to high levels of 2,4-D was carried out. When C. necator JMP134 was introduced into soil microcosms, the rate of 2,4-D removal increased only slightly. This correlated with the poor survival of the strain, as judged by 16S rRNA gene terminal restriction fragment length polymorphism (T-RFLP) profiles, and the semi-quantitative detection of the pJP4-borne tfdA gene sequence, encoding the first step in 2,4-D degradation. After 3 days of incubation in irradiated soil microcosms, the survival of strain JMP134 dramatically improved and the herbicide was completely removed. The introduction of strain JMP134 into native soil microcosms did not produce detectable changes in the structure of the bacterial community, as judged by 16S rRNA gene T-RFLP profiles, but provoked a transient increase of signals putatively corresponding to protozoa, as indicated by 18S rRNA gene T-RFLP profiling. Accordingly, a ciliate able to feed on C.␣necator JMP134 could be isolated after soil enrichment. In␣native soil microcosms, C. necator JMP134 survived better than Escherichia coli DH5α (pJP4) and similarly to Pseudomonas putida KT2442 (pJP4), indicating that species specific factors control the survival of strains harbouring pJP4. The addition of cycloheximide to soil microcosms strongly improved survival of these three strains, indicating that the eukaryotic microbiota has a strong negative effect in bioaugmentation with catabolic bacteria.     

Isolation,Characterization of a Strain Capable of Degrading Imazethapyr and Its Use in Degradation of the Herbicide in Soil

One strain of bacterium IM-4, capable of degrading imazethapyr (IMZT), was isolated from the IMZT-contaminated soil. The isolate was identified as Pseudomonas sp. according to its physiological characteristics, biochemical tests, and 16S rRNA gene phylogenetic analysis. This strain could utilize IMZT as the sole carbon and energy source. About 73.4% of the 50 mg l⁻¹ initially added IMZT was degraded after 7 days of inoculation with strain IM-4. This strain also showed the capability to degrade other imidazolinone herbicides such as imazapyr, imazapic, and imazamox. The inoculation strain IM-4 to soil treated with IMZT resulted in a higher degradation rate than in noninoculated soil regardless if the soil was sterilized or nonsterilized. Inoculation of strain IM-4 could also mitigate the phytotoxic effects of IMZT on the growth of maize.     

SulE, a sulfonylurea herbicide de-esterification esterase from Hansschlegelia zhihuaiae S113

De-esterification is an important degradation or detoxification mechanism of sulfonylurea herbicide in microbes and plants. However, the biochemical and molecular mechanisms of sulfonylurea herbicide de-esterification are still unknown. In this study, a novel esterase gene, sulE, responsible for sulfonylurea herbicide de-esterification, was cloned from Hansschlegelia zhihuaiae S113. The gene contained an open reading frame of 1,194 bp, and a putative signal peptide at the N terminal was identified with a predicted cleavage site between Ala37 and Glu38, resulting in a 361-residue mature protein. SulE minus the signal peptide was synthesized in Escherichia coli BL21 and purified to homogeneity. SulE catalyzed the de-esterification of a variety of sulfonylurea herbicides that gave rise to the corresponding herbicidally inactive parent acid and exhibited the highest catalytic efficiency toward thifensulfuron-methyl. SulE was a dimer without the requirement of a cofactor. The activity of the enzyme was completely inhibited by Ag(+), Cd(2+), Zn(2+), methamidophos, and sodium dodecyl sulfate. A sulE-disrupted mutant strain, ΔsulE, was constructed by insertion mutation. ΔsulE lost the de-esterification ability and was more sensitive to the herbicides than the wild type of strain S113, suggesting that sulE played a vital role in the sulfonylurea herbicide resistance of the strain. The transfer of sulE into Saccharomyces cerevisiae BY4741 conferred on it the ability to de-esterify sulfonylurea herbicides and increased its resistance to the herbicides. This study has provided an excellent candidate for the mechanistic study of sulfonylurea herbicide metabolism and detoxification through de-esterification, construction of sulfonylurea herbicide-resistant transgenic crops, and bioremediation of sulfonylurea herbicide-contaminated environments.     

Biodegradation of mixture containing monohydroxybenzoate isomers by <Emphasis Type="Italic">Acinetobacter calcoaceticus</Emphasis>

A bacterial strain capable of utilizing a mixture containing 2-hydroxybenzoic acid (2-HBA), 3-hydroxybenzoic acid (3-HBA) and 4-hydroxybenzoic (4-HBA) acid was isolated through enrichment from a soil sample. Based on 16SrDNA sequencing, the microorganism was identified as Acinetobacter calcoaceticus. The sequence of biodegradation of the three isomers when provided as a mixture (0.025%, w/v each) was elucidated. The dihydroxylated metabolites formed from the degradation of 2-HBA, 3-HBA and 4-HBA were identified as catechol, gentisate and protocatechuate, respectively, using the cell-free supernatant and cell-free crude extracts. Monooxygenases and dioxygenases that were induced in the cells of Acinetobacter calcoaceticus in response to growth on mixture containing 2-HBA, 3-HBA and 4-HBA could be detected in cell-free extracts. These data revealed the pathways operating in Acinetobacter calcoaceticus for the sequential metabolism of monohydroxybenzoate isomers when presented as a mixture.     

Co-metabolic degradation of tribenuron methyl,a sulfonylurea herbicide,by Pseudomonas sp. strain NyZ42

A co-metabolic degradation of tribenuron methyl bacterial strain NyZ42 was isolated from polluted agricultural soil and classified as genus Pseudomonas by its 16S rRNA gene sequencing. The degradation efficiency of tribenuron methyl was about 80% of the originally supplemented 200 mg l⁻¹ tribenuron methyl in liquid minimal medium within four days, when either glucose or succinate was used as a supplemental carbon source. Three intermediates formed during the degradation of tribenuron methyl mediated by strain NyZ42 were captured by LC-MS, and two alternative pathways were proposed for the microbial mediated tribenuron methyl degradation, via either cleavage of the sulfonylurea bridge or saponification of alkyl-group. Furthermore, inoculation of strain NyZ42 enhanced the degradation of tribenuron methyl in the sterilized soil samples, although the biodegradation/co-metabolism ability of NyZ42 was not obvious in the nonsterilized soil samples when compared with the indigenous microbial consortium under current laboratory conditions.     

三七皂苷类自毒物质降解细菌分离及其降解特性

三七是我国的名贵药材,但由于连作障碍发生严重,因此土壤中自毒物质的积累成为导致三七连作障碍发生的主要原因之一。生物降解土壤中的自毒物质是缓解连作障碍的有效措施,为筛选并利用降解菌使土壤中皂苷类自毒物质快速消减,该研究以皂苷类自毒物质为筛选靶标,采用富集和驯化策略,从连作三七根际土壤中分离、筛选三七皂苷类自毒物质降解细菌,结合16S rRNA基因测序对高活性菌株进行分类鉴定,并对筛选得到的高活性菌株SC3的降解特性进行了研究。结果表明:(1)从三七根际土壤中成功分离出8株潜在自毒物质降解细菌,初筛评价结果显示SC3菌株对三七总皂苷的降解率最高,达87.42%。(2)通过16S rRNA基因序列分析,编号SC3的高活性菌株被鉴定为寡养单胞菌属(Stenotrophomonas)细菌。(3)在相同培养条件下,菌株SC3对单体皂苷Rb₁的降解效果强于对Rg₁的降解。(4)在液体培养条件下,底物浓度、接种量和培养温度均会显著影响SC3菌株对单体皂苷Rb₁的降解效果。综上表明,采用富集和驯化策略可以有效筛选自毒物质降解细菌,SC3菌株具有消除连作土壤中皂苷类自毒物质的潜力。该研究结果为连作土壤修复提供了生物资源,并为今后深入研究皂苷降解机制提供了理论依据。     

Characterization of <Emphasis Type="Italic">Rhodococcus wratislaviensis</Emphasis> strain J3 that degrades 4-nitrocatechol and other nitroaromatic compounds

The bacterial strain J3 was isolated from soil by selective enrichment on mineral medium containing 4-nitrocatechol as the sole carbon and energy source. This strain was identified as Rhodococcus wratislaviensis on the basis of morphology, biochemical, physiological and chemotaxonomic characterization and complete sequencing of the 16S rDNA gene. The isolated bacterium could utilize 4-nitrocatechol, 3-nitrophenol and 5-nitroguaiacol as sole carbon and energy sources. Stoichiometric release of nitrites was measured during degradation of 4-nitrocatechol both in growing cultures and for stationary phase cells. The J3 strain was unable to degrade 4-nitroguaiacol, 2-nitrophenol, 4-nitrophenol, 2,4-dinitrobenzoic acid, 4,5-dimethoxy-2-nitrobenzoic acid and 2,3-difluoro-6-nitrophenol. The J3 strain is deposited in the Czech Collection of Microorganisms as CCM 4930.     

一株3-苯氧基苯甲酸降解菌的筛选及其协同Bacillus licheniformis G-04降解高效氯氰菊酯的研究

【目的】从长期受拟除虫菊酯类农药污染的白菜根系土壤分离1株3-苯氧基苯甲酸(3-phenoxybenzoic acid, 3-PBA)降解菌,并探究其与Bacillus licheniformis G-04协同作用对高效氯氰菊酯(beta-cypermethrin,Beta-CP)的降解及污染土壤的生物修复,为土壤农药残留危害处理提供优良菌种。【方法】采用富集驯化、筛选纯化方法,筛选3-PBA降解菌,并通过形态和生理生化特征以及16S rRNA序列分析进行鉴定。利用Origin 8.0分析3-PBA降解菌与B. licheniformis G-04的生长降解动力学过程。同时,采用高效液相色谱法评估两菌株协同降解Beta-CP的能力及其对受Beta-CP污染土壤的修复作用。【结果】筛选得到1株3-PBA高效降解菌HA516,48 h对3-PBA (100 mg/L)的降解率达到87.73%,经鉴定为皮特不动杆菌(Acinetobacter pittii);构建了该菌株和B. licheniformis G-04的生长降解动力学方程,结果表明模型与实验数据能较好拟合;以6.7∶3.3的接种比例先接种B. licheniformis G-04,24 h后再接入A. pittii HA516协同作用,在48 h,Beta-CP (50 mg/L)的降解率达78.37%,较单菌株(B. licheniformisG-04)的降解率(40.47%)提高了37.90%,半衰期从58.39h缩短为24.51h。土壤修复实验表明,第7天协同组对Beta-CP(30mg/kg)的降解率较单菌株提高了33.26%,达到79.27%。【结论】A.pittiiHA516是1株3-PBA高效降解菌,能与B. licheniformis G-04协同增效降解Beta-CP,可作为修复3-PBA或拟除虫菊酯类农药污染的优良微生物资源。     

Biodegradation of methyl parathion and <Emphasis Type="Italic">p</Emphasis>-nitrophenol: evidence for the presence of a <Emphasis Type="Italic">p</Emphasis>-nitrophenol 2-hydroxylase in a Gram-negative <Emphasis Type="Italic">Serratia</Emphasis> sp. strain DS001

A soil bacterium capable of utilizing methyl parathion as sole carbon and energy source was isolated by selective enrichment on minimal medium containing methyl parathion. The strain was identified as belonging to the genus Serratia based on a phylogram constructed using the complete sequence of the 16S rRNA. Serratia sp. strain DS001 utilized methyl parathion, p-nitrophenol, 4-nitrocatechol, and 1,2,4-benzenetriol as sole carbon and energy sources but could not grow using hydroquinone as a source of carbon. p-Nitrophenol and dimethylthiophosphoric acid were found to be the major degradation products of methyl parathion. Growth on p-nitrophenol led to release of stoichiometric amounts of nitrite and to the formation of 4-nitrocatechol and benzenetriol. When these catabolic intermediates of p-nitrophenol were added to resting cells of Serratia sp. strain DS001 oxygen consumption was detected whereas no oxygen consumption was apparent when hydroquinone was added to the resting cells suggesting that it is not part of the p-nitrophenol degradation pathway. Key enzymes involved in degradation of methyl parathion and in conversion of p-nitrophenol to 4-nitrocatechol, namely parathion hydrolase and p-nitrophenol hydroxylase component “A” were detected in the proteomes of the methyl parathion and p-nitrophenol grown cultures, respectively. These studies report for the first time the existence of a p-nitrophenol hydroxylase component “A”, typically found in Gram-positive bacteria, in a Gram-negative strain of the genus Serratia. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Study of Biochemical Pathway and Enzyme Involved in Metsulfuron-Methyl Degradation by <Emphasis Type="Italic">Ancylobacter</Emphasis> sp. XJ-412-1 Isolated from Soil

Ancylobacter sp. XJ-412-1, capable of degrading metsulfuron-methyl, was isolated from sulfonylurea-contaminated soil. When metsulfuron-methyl was provided as the sole carbon source, more than 90.5% of metsulfuron-methyl at concentration of 50 mg l⁻¹ was degraded by strain XJ-412-1 after incubation at 30°C for 7 days. The initial degradation products of metsulfuron-methyl (MSM), thifensulfuron-methyl (TSM), and bensulfuron-methyl (BSM) by XJ-412-1 were identified as corresponding deesterified derivatives by liquid chromatography-mass spectrometry, which indicated a primary pathway of the deesterification of these three sulfonylurea herbicides. The carboxyesterase activity of the cell-free extracts was assayed and strongly inhibited by 4-chloromercuribenzoic acid (PCMB), diethyl pyrocarbonate (DEPC), phenylmethylsulfonyl fluoride (PMSF), and malathion.     

Growth promoting effect of a transgenic <Emphasis Type="Italic">Bacillus mucilaginosus</Emphasis> on tobacco planting

In this study, we have investigated the plant growth promoting effect of Bacillus mucilaginosus strain D₄B₁, a rhizosphere soil organism, and its transgenic strain NKTS-3 on tobacco planting. The transgenic strain contains a phytase expression cassette that can express high active phytase extracellularly and hydrolyze phytate in the soil to liberate inorganic phosphorus for the growth of tobacco plants. Greenhouse study and field experiments showed that both wild-type B. mucilaginosus and the transgenic strain could promote tobacco plant growth. Moreover, the transgenic strain promoted tobacco plant growth (235% more than control in pot experiments and 125% more than control in field experiments) was higher than the wild-type B. mucilaginosus (183% more than control in pot experiments and 108% more than control in field experiments). In addition, the inoculation with transgenic rhizobacteria could significantly improve root acquisition of phosphorus and increase the phosphorus content of the plant.     

Chemical disinfestation and metabolic integrity of soil

Summary Field disinfestation in autumn with normal or increased dosages of 1,3-dichloropropene, metham-sodium or chloroform, and in spring with ethoprophos, did not, or hardly, affect the degradationin situ of some herbicides applied in spring. However, during laboratory incubation of samples from the disinfested plots, sometimes decreased herbicide degradation rates or increased lag phases were found.The top few centimetres of the field soil, on which the herbicides were sprayed, apparently largely escaped fumigation. Accordingly, effects of fumigation on herbicide degradation, organic matter and N metabolism were stronger in samples from the 10–20 cm layer than in samples from 0–10 cm.In the laboratory fumigation of soil samples with CHCl₃ was much more drastic in inhibiting herbicide degradation, N mineralisation and nitrification; inoculation with 10% fresh soil, however, greatly accelerated the recovery of these processes. Therefore, in practice prolonged or drastic effects of chemical soil disinfestation on metabolic integrity of the soil are not to be expected.     

Degradation of cyclohexylamine by a new isolate of <Emphasis Type="Italic">Pseudomonas plecoglossicida</Emphasis>

A strain utilizing cyclohexylamine as the sole source of carbon and nitrogen, designated NyZ12, was isolated from soil and identified by 16S rDNA sequencing as Pseudomonas plecoglossicida. This bacterium released ammonia into the medium when grown on cyclohexylamine, and also grows readily on cyclohexanone as the sole carbon source, suggesting that degradation involves an initial deamination step.     

Degradation of Bromoxynil Octanoate by Strain Acinetobacter sp. XB2 Isolated from Contaminated Soil

Bromoxynil octanoate (BOO), the most widespread herbicide applied to maize, is potentially toxic to both animals and humans. In this article, a highly effective BOO-degrading bacterial strain, XB2, was isolated from the soil of a herbicide factory. The strain was identified as an Acinetobacter sp. based on its 16S rRNA gene sequence analysis, morphological, physiological, and biochemical properties. This strain could use BOO as its sole carbon source and could degrade 100?mg?l(-1) BOO to non-detectable levels in 72?h (h). The optimal pH and temperature for strain XB2's growth and degradation of BOO in MSM are 7.0 and 30°C, respectively. We propose the following pathway of BOO degradation by strain XB2: the first step is the scission of the ester bond to form bromoxynil, bromoxynil then transformed to 3,5-dibromo-4-hydroxybenzoic acid?due to the hydrolysis of nitriles, and debromination finally results in the formation of 3-bromo-4-hydroxybenzoic acid. Inoculating BOO-treated soil samples with strain XB2 resulted in a higher rate of BOO degradation than in non-inoculated soil, regardless of whether the soil had previously been sterilized.     

Isolation from Agricultural Soil and Characterization of a Sphingomonas sp. Able To Mineralize the Phenylurea Herbicide Isoproturon

A soil bacterium (designated strain SRS2) able to metabolize the phenylurea herbicide isoproturon, 3-(4-isopropylphenyl)-1,1-dimethylurea (IPU), was isolated from a previously IPU-treated agricultural soil. Based on a partial analysis of the 16S rRNA gene and the cellular fatty acids, the strain was identified as a Sphingomonas sp. within the α-subdivision of the proteobacteria. Strain SRS2 was able to mineralize IPU when provided as a source of carbon, nitrogen, and energy. Supplementing the medium with a mixture of amino acids considerably enhanced IPU mineralization. Mineralization of IPU was accompanied by transient accumulation of the metabolites 3-(4-isopropylphenyl)-1-methylurea, 3-(4-isopropylphenyl)-urea, and 4-isopropyl-aniline identified by high-performance liquid chromatography analysis, thus indicating a metabolic pathway initiated by two successive N-demethylations, followed by cleavage of the urea side chain and finally by mineralization of the phenyl structure. Strain SRS2 also transformed the dimethylurea-substituted herbicides diuron and chlorotoluron, giving rise to as-yet-unidentified products. In addition, no degradation of the methoxy-methylurea-substituted herbicide linuron was observed. This report is the first characterization of a pure bacterial culture able to mineralize IPU.     

Isolation and characterization of an isoproturon mineralizing <Emphasis Type="Italic">Sphingomonas</Emphasis> sp. strain SH from a French agricultural soil

The phenylurea herbicide isoproturon, 3-(4-isopropylphenyl)-1,1-dimethylurea (IPU), was found to be rapidly mineralized in an agricultural soil in France that had been periodically exposed to IPU. Enrichment cultures from samples of this soil isolated a bacterial strain able to mineralize IPU. 16S rRNA sequence analysis showed that this strain belonged to the phylogeny of the genus Sphingomonas (96% similarity with Sphingomonas sp. JEM-14, AB219361) and was designated Sphingomonas sp. strain SH. From this strain, a partial sequence of a 1,2-dioxygenase (catA) gene coding for an enzyme degrading catechol putatively formed during IPU mineralization was amplified. Phylogenetic analysis revealed that the catA sequence was related to Sphingomonas spp. and showed a lack of congruence between the catA and 16S rRNA based phylogenies, implying horizontal gene transfer of the catA gene cluster between soil microbiota. The IPU degrading ability of strain SH was strongly influenced by pH with maximum degradation taking place at pH 7.5. SH was only able to mineralize IPU and its known metabolites including 4-isopropylaniline and it could not degrade other structurally related phenylurea herbicides such as diuron, linuron, monolinuron and chlorotoluron or their aniline derivatives. These observations suggest that the catabolic abilities of the strain SH are highly specific to the metabolism of IPU.     

Isolation of Fenitrothion-degrading Strain Burkholderia sp. FDS-1 and Cloning of mpd Gene

A short rod shaped, gram-negative bacterium strain Burkholderia sp. FDS-1 was isolated from the sludge of the wastewater treating system of an organophosphorus pesticides manufacturer. The isolate was capable of using fenitrothion as the sole carbon source for its growth. FDS-1 first hydrolyzed fenitrothion to 3-methyl-4-nitrophenol, which was further metabolized to nitrite and methylhydroquinone. The addition of other carbon source and omitting phosphorus source had little effect on the hydrolysis of fenitrothion. The gene encoding the organophosphorus hydrolytic enzyme was cloned and sequenced. The sequence was similar to mpd, a gene previously shown to encode a parathion-methyl-hydrolyzing enzyme in Plesiomonas sp. M6. The inoculation of strain FDS-1 (10⁶ cells g⁻¹) to soil treated with 100 mg fenitrothion emulsion kg⁻¹ resulted in a higher degradation rate than in noninoculated soils regardless of the soil sterilized or nonsterilized. These results highlight the potential of this bacterium to be used in the cleanup of contaminated pesticide waste in the environment. Zhonghui Zhang, Qing Hong: Both authors contributed equally to this work