Inhibition of Pigment Biosynthesis in Cucumber Cotyledons by Isoxaflutole

Isoxaflutole [5-cyclopropyl-4-(2-methylsulphonyl-4-trifluromethylbenzoyl)isoxazole] is a new preemergence herbicide for broad-spectrum weed control in maize. The effect of isoxaflutole on chlorophyll (Chl) and carotenoid (Car) biosynthesis was investigated in cucumber (Cucumis sativus L.) cotyledons. Etiolated tissue was incubated with 5 mM isoxaflutole for 24 h and irradiated (60 mol m^-2 s^-1). The irradiation for 3 h did not reduce Chl a, Chl b, and Car contents, but after a 28-h irradiation the contents of Chl a and Car decreased by 35 and 15 %, respectively, and the content of Chl b increased by 24 %. Increasing the concentration of isoxaflutole beyond 5 mM resulted in reduction of Chl a (71 %), Chl b (20 %), and Car (31 %) contents. Similarly, increase in irradiance from 60 to 180 mol m^-2 s^-1 resulted in larger reduction of Chl and Car contents. Exogenously supplied 5-aminolevulinic acid did not reverse the isoxaflutole-inhibited Chl synthesis, whereas an exogenously supplied homogentisic acid lactone reversed the inhibition of pigment synthesis due to isoxaflutole.     

The effect of soil pH on chickpea (Cicer arietinum) genotype sensitivity to isoxaflutole

A glasshouse experiment was conducted to investigate the effect of soil pH on chickpea (Cicer arietinum) tolerance to isoxaflutole applied pre-emergence at 0, 75 (recommended rate) and 300 g a.i. ha⁻¹. For this study, the variables examined were two desi chickpea genotypes (97039-1275 as a tolerant line and 91025-3021 as a sensitive line) and four pH levels (5.1, 6.9, 8.1, and 8.9). The results demonstrated differential tolerances among chickpea genotypes to isoxaflutole at different rates and soil pH levels. Isoxaflutole applied pre-emergence resulted in increased phytotoxicity with increases in soil pH and herbicide rate. Even the most tolerant chickpea genotype was damaged when exposed to higher pH and herbicide rates, as indicated by increased leaf chlorosis and significant reductions in plant height, and shoot and root dry weight. The effects were more severe with the sensitive genotype. The susceptibility of chickpea to this herbicide depends on genotype and soil pH which should be taken into account in breeding new lines, and in the agronomy of chickpea production.     

Phytotoxicity of isoxaflutole to Phalaris minor Retz.

Littleseed canarygrass (Phalaris minor Retz.) is a major weed in wheat fields, and has developed resistance to the commonly used herbicide isoproturon. This study explores the potential use of isoxaflutole, a pre-emergence herbicide, to control littleseed canarygrass. Greenhouse studies were carried out to determine the phytotoxicity of isoxaflutole in relation to shoot height, fresh shoot biomass and leaf chlorophyll concentration of wheat and littleseed canarygrass. Electron microscopy was used to examine any damage to leaf chloroplast at ultrastructural level. Results indicate that isoxaflutole (0.5 mg/L) significantly reduced the shoot height of littleseed canarygrass (39.6%), but no significant reduction in the shoot height of wheat was observed (9.6%) when compared to control. None of the concentrations (0.05, 0.1, 0.5 and 1 mg/L) of isoxaflutole altered soil chemistry in relation to pH, organic matter, macro or micro inorganic ions. While untreated littleseed canarygrass leaves had elongated chloroplast, starch grains and small number of plastoglobuli; treated littleseed canarygrass leaves had swollen chloroplast, large number of plastoglobuli, and a lack of starch grains. We conclude that isoxaflutole can be an effective herbicide for controlling littleseed canarygrass.     

Effect of Rice Straw Incorporation on Phytotoxicity of Isoxaflutole to an Exotic Weed Phalaris minor Retz.

Phalaris minorRetz. is a major exotic annual weed in the wheat (Triticum aestivum L.) crop. Unharvested rice (Oryza sativa L.) straw, unburned and burned, is often incorporated in the field prior to cultivating wheat. Isoxaflutole (Balance), a pre-emergent systemic soil applied herbicide, has potential to control P. minor. Glasshouse experiments were conducted to determine the phytotoxicity of isoxaflutole defined by reductions in relation to shoot length of P. minor when grown in unamended soil or soil amended with unburned or burned rice straw. A 120 g soil was amended with 0, 1, 2 and 4 g of unburned or burned rice straw, and placed in 150 mL styrofoam pots. Appropriate amount of isoxaflutole (75% active ingredient, ai) was added to pots to get final concentration of 0, 7.5, 30, 60 and 120 μg ai/pot. Unamended soil and soil amended with unburned or burned rice straw were analyzed for pH and organic matter; two important determinants of isoxaflutole activity. Results indicate a significant reduction in shoot length of P. minor when grown in soil treated with isoxaflutole at 30, 60 or 120 μg ai/pot. Inhibition in the shoot length of P. minor was observed when soil amended with unburned straw was treated with isoxaflutole at 7.5 and 30 μg ai/pot compared with unamended soil treated with similar amounts of isoxaflutole. No significant change in isoxaflutole toxicity was observed when soil amended with unburned straw was treated with isoxaflutole at 60 and 120 lg ai/pot compared with unamended soil treated with similar amounts of isoxaflutole. Isoxaflutole phytotoxicity to P. minor shoot length was eliminated when soil amended with burned straw was treated with isoxaflutole at 7.5 and 30 μg ai/pot. P. minor shoot length was greater when soil amended with burned straw was treated with isoxaflutole at 60 and 120 μg ai/pot relative to herbicide-treated unamended soils. We conclude that incorporation of burned rice straw greatly reduces the phytotoxicity of isoxaflutole toP. minor.     

Degradation of the herbicide diclofop-methyl in soil and influence of pesticide mixtures on its persistence

The degradation of the herbicide [¹⁴C]-diclofopmethyl was investigated in moist parabrown podzol soil at 22°C. Radiochemical procedures were used to monitor the herbicide breakdown. The mineralization of the uniformly labelled aromatic ring was pursued by trapping the¹⁴CO₂ generated for 96 days. Diclofop-methyl was rapidly degraded in the soil with a half-life of about 8 days. The major breakdown product was the corresponding acid-diclofop, formed by a very rapid hydrolysis of the esterbond. With time the acid appeared to undergo strong binding or complexing to the soil. An intermediate 4-(2,4-dichlorophenoxy) phenol was recovered from the treated soil. Concentration of the phenoxyphenol increased upto 6 days followed by quick decline. Insecticide combination of parathion + Demeton-Smethylsulphoxide partially inhibited diclofop degradation in the soil     

The effects of the herbicide quinclorac on shoot growth in tomato is alleviated by inhibitors of ethylene biosynthesis and by the presence of an antisense construct to the 1-aminocyclopropane-1-carboxylic acid (ACC) synthase gene in transgenic plants

Reduction of shoot growth, leaf epinasty and chlorosis in young tomato plants (Lycopersicon esculentum Mill. cv. Hellfrucht/Frühstamm) treated hydroponically with 10^-7 M of the herbicide quinclorac were partially compensated when the plants were simultaneously sprayed with salicyclic acid or the oxime ether derivative PACME. Since salicyclic acid and PACME are known inhibitors of ethylene biosynthesis, it is suggested that this pathway is implicated in quinclorac action. Further support for this hypothesis was obtained in experiments with transgenic tomato plants containing an antisense gene to 1-aminocyclopropane-1-carboxylic acid (ACC) synthase in ethylene biosynthesis. When quinclorac was applied via the root antisense plants showed reduced phenotypical alterations compared to those of wild-type plants.     

Isoxaflutole treatment leads to reversible tissue bleaching and allows for more effective detection of GFP in transgenic soybean tissues

The effects of the herbicide isoxaflutole (IFT) on tissue growth and the detection of green fluorescent protein (GFP) in transgenic embryogenic soybean tissues were evaluated using image analysis. The inclusion of this “bleaching” herbicide at 3 or 10 mg l⁻¹ in a standard soybean embryo proliferation medium resulted in a change in tissue color from green to non-pigmented over the course of a 4-wk experiment. Although the loss in pigmentation was observed in transgenic and non-transformed control tissues, tissue growth remained unaffected. GFP expression in three different transgenic soybean clones, representing low to moderate GFP expression levels, was easily detected and quantified using image analysis following culture of the tissues on an IFT-containing medium. Quantification of GFP in tissues from the same clones cultured in the absence of IFT, however, was difficult using image analysis. After transfer of transgenic embryogenic tissue from a medium containing IFT to a medium without IFT, the growth of pigment-containing tissue resumed. The bleaching effects from this herbicide appear to be reversible and make IFT and possibly other bleaching herbicides useful in the analysis of GFP expression in tissues, where interference from chlorophyll is problematic.     

Nitrogen Control of Atrazine Utilization in Pseudomonas sp. Strain ADP

Pseudomonas sp. strain ADP uses the herbicide atrazine as the sole nitrogen source. We have devised a simple atrazine degradation assay to determine the effect of other nitrogen sources on the atrazine degradation pathway. The atrazine degradation rate was greatly decreased in cells grown on nitrogen sources that support rapid growth of Pseudomonas sp. strain ADP compared to cells cultivated on growth-limiting nitrogen sources. The presence of atrazine in addition to the nitrogen sources did not stimulate degradation. High degradation rates obtained in the presence of ammonium plus the glutamine synthetase inhibitor MSX and also with an Nas⁻ mutant derivative grown on nitrate suggest that nitrogen regulation operates by sensing intracellular levels of some key nitrogen-containing metabolite. Nitrate amendment in soil microcosms resulted in decreased atrazine mineralization by the wild-type strain but not by the Nas⁻ mutant. This suggests that, although nitrogen repression of the atrazine catabolic pathway may have a strong impact on atrazine biodegradation in nitrogen-fertilized soils, the use of selected mutant variants may contribute to overcoming this limitation.     

Synthesis and properties of a photoaffinity probe for the glucagon receptor in hepatocyte plasma membranes

The reaction of glucagon with 4-fluoro-3-nitrophenylazide has been shown to afford the photosensitive derivative, N^?-4-azido-2-nitrophenyl-glucagon. The structure and properties of this derivative were established by amino acid analysis, absorption and fluorescence spectroscopy, deamination, Edman degradation and photolysis. This photoaffinity derivative of glucagon has been used to label specifically glucagon binding sites on hepatocyte plasma membranes.     

In Situ Exposure to Low Herbicide Concentrations Affects Microbial Population Composition and Catabolic Gene Frequency in an Aerobic Shallow Aquifer

The aim of this study was to evaluate how the in situ exposure of a Danish subsurface aquifer to phenoxy acid herbicides at low concentrations (<40 μg l⁻¹) changes the microbial community composition. Sediment and groundwater samples were collected inside and outside the herbicide-exposed area and were analyzed for the presence of general microbial populations, Pseudomonas bacteria, and specific phenoxy acid degraders. Both culture-dependent and culture-independent methods were applied. The abundance of microbial phenoxy acid degraders (10⁰ to 10⁴ g⁻¹ sediment) was determined by most probable number assays, and their presence was only detected in herbicide-exposed sediments. Similarly, PCR analysis showed that the 2,4-dichlorophenoxyacetic acid degradation pathway genes tfdA and tfdB (10² to 10³ gene copies g⁻¹ sediment) were only detected in sediments from contaminated areas of the aquifer. PCR-restriction fragment length polymorphism measurements demonstrated the presence of different populations of tfd genes, suggesting that the in situ herbicide degradation was caused by the activity of a heterogeneous population of phenoxy acid degraders. The number of Pseudomonas bacteria measured by either PCR or plating on selective agar media was higher in sediments subjected to high levels of phenoxy acid. Furthermore, high numbers of CFU compared to direct counting of 4′,6-diamidino-2-phenylindole-stained cells in the microscope suggested an increased culturability of the indigenous microbial communities from acclimated sediments. The findings of this study demonstrate that continuous exposure to low herbicide concentrations can markedly change the bacterial community composition of a subsurface aquifer.     

Glyphosate tolerance by Clitoria ternatea and Neonotonia wightii plants involves differential absorption and translocation of the herbicide

Glyphosate tolerance by Clitoria ternatea, Neonotonia wightii and Amaranthus hybridus was studied in whole plants from Mexico. Experiments in a controlled growth chamber showed both legumes to be highly tolerant of glyphosate, with and ED₅₀ values of 600.18 g ae ha^?C1 for C. ternatea and 362.94 g ae ha^?C1 for N. wightii. On the other hand, A. hybridus was highly susceptible to the herbicide (ED₅₀?=?42.22 g ae ha^?C1). Shikimate accumulation peaked 96 h after treatment in the tolerant plants and the susceptible weed under 500 g ae ha^?C1 glyphosate. The shikimic acid content of whole leaves was 4.0 and 5.0 times higher in the susceptible weed than in N. wightii and C. ternatea, respectively. ¹⁴C-glyphosate absorption and translocation tests showed A. hybridus to absorb 30% more herbicide than the legumes 24 h after glyphosate foliar application. ¹⁴C-glyphosate translocation as measured by quantified autoradiography revealed increased translocation of the herbicide to untreated leaves and roots in A. hybridus relative to the two legumes. The cuticular surface of A. hybridus exhibited very low wax coverage relative to the epicuticular surface of N. wightii and, especially, C. ternatea. No significant degradation of glyphosate to aminomethylphosphonic acid and glyoxylate metabolites was detected among the tolerant leguminous plants or the susceptible weed population. These results indicate that the high glyphosate tolerance of Clitoria ternatea and Neonotonia wightii is mainly a result of poor penetration and translocation of the herbicide to apical growing points in their plants.     

Experimental complexities in evaluating the comparative phytotoxicity of chemicals with different modes of action

Careful attention should be paid to bioassay experiments to examine the comparative phytotoxicity of chemicals with different modes of actions. Experimental complexities in examining comparative phytotoxicity of chemicals with differing modes of action are determined and discussed to appreciate the importance of relevant secondary effects that can be quickly measured. The chemicals selected were: benzoic acid, isoxaflutole and rimsulfuron. Data on shoot and root length of 7-day-old mustard (Brassica napus L.) seedlings, shoot height of 4-week-old mustard plants and total leaf chlorophyll concentrations were determined when plants were grown in soil treated with different concentrations of the three chemicals. Scanning electron microscope (SEM) studies were conducted to determine any damage to mustard root hairs after treatment. Root growth of 7-day-old mustard seedlings was reduced when treated with different concentrations of benzoic acid or rimsulfuron. Root growth of mustard seedlings, however, largely remained unaffected when plants were grown in soil treated with isoxaflutole. While no significant reduction in either chlorophyll concentration or shoot height of 4-week-old mustard plants was observed when treated with soil-applied benzoic acid, both parameters were inhibited when mustard plants were treated with isoxaflutole or rimsulfuron. SEM studies revealed significant damage to root hairs in a 7-day-old mustard seedlings when plants were grown in soil treated with 500, 1000 and 2000 mg/L benzoic acid, and 0.5 mg/L rimsulfuron. No such damage was observed when mustard was grown in soil treated with isoxaflutole.     

Action of 2,4-DB and dalapon on the symbiotic properties ofLotus corniculatus (birdsfoot trefoil)

Summary Field trials carried out in 1965 and 1966 showed that 2,4-DB, alone or in combination with dalapon, reduced nodulation and tended to decrease the efficiency of nitrogen fixation in birdsfoot trefoil. Dalapon appeared to enhance the inhibitory action of 2,4-DB on nodulation. No obvious cytological differences could be detected in the nodules or in the isolated bacteroids of field-treated and untreated plants. Under growth chamber conditions, 2,4-DB drastically reduced trefoil growth and nodulation particularly in treatments where the herbicide came directly in contact with the plants. It appears that the reduction in nodulation and nitrogen fixation is a result of plant damage and abnormal root growth caused by 2,4-DB application.Autoradiographs indicated that the translocation of the herbicide was rapid, with detectable concentrations observed in young leaves, leafveins, roots, and nodules 12 hours after leaf-feeding of 2,4-DB-1-C¹⁴. The radio-activity appeared to accumulate with time (up to 5 days) in the growing root tips and nodules. Fractionation of excised nodules from trefoil plants demonstrated the presence of radioactivity in the cell debris, bacteroids, 29,000g pellet, plant ribosomes, and the soluble portion. The greatest accumulation of radioactivity occurred in the soluble fraction.The degradation of 2,4-DB and 2,4-D in trefoil was demonstrated by the evolution of C¹⁴O₂ from non-nodulated and aseptically growing plants leaf-fed with 2,4-DB-1-C¹⁴ or 2,4-D-1-C¹⁴.4-(2,4-dichlorophenoxy) butyric acid.2,2 dichloropropionic acid.     

Comparing Metabolic Functionalities,Community Structures,and Dynamics of Herbicide-Degrading Communities Cultivated with Different Substrate Concentrations

Two 4-chloro-2-methylphenoxyacetic acid (MCPA)-degrading enrichment cultures selected from an aquifer on low (0.1 mg liter⁻¹) or high (25 mg liter⁻¹) MCPA concentrations were compared in terms of metabolic activity, community composition, population growth, and single cell physiology. Different community compositions and major shifts in community structure following exposure to different MCPA concentrations were observed using both 16S rRNA gene denaturing gradient gel electrophoresis fingerprinting and pyrosequencing. The communities also differed in their MCPA-mineralizing activities. The enrichments selected on low concentrations mineralized MCPA with shorter lag phases than those selected on high concentrations. Flow cytometry measurements revealed that mineralization led to cell growth. The presence of low-nucleic acid-content bacteria (LNA bacteria) was correlated with mineralization activity in cultures selected on low herbicide concentrations. This suggests that LNA bacteria may play a role in degradation of low herbicide concentrations in aquifers impacted by agriculture. This study shows that subpopulations of herbicide-degrading bacteria that are adapted to different pesticide concentrations can coexist in the same environment and that using a low herbicide concentration enables enrichment of apparently oligotrophic subpopulations.     

A new concept for reduction of diffuse contamination by simultaneous application of pesticide and pesticide-degrading microorganisms

Pesticide residues and their transformation products are frequently found in groundwater and surface waters. This study examined whether adding pesticide-degrading microorganisms simultaneously with the pesticide at application could significantly reduce diffuse contamination from pesticide use. Degradation of the phenoxyacetic acid herbicides MCPA (4-chloro-2-methylphenoxyacetic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid) was studied in soil microcosm experiments after simultaneous spraying of herbicide and herbicide-degrading bacteria on an agricultural soil and on a sand with low degradation potential. The latter represented pesticide use on non-agricultural soils poor in microbial activity. Degradation and possible loss of herbicidal effect were also tested in a system with plants and the amounts of bacteria needed to give satisfactory MCPA-degradation rate and the survival of degrading bacteria in formulated MCPA were determined. The results showed >80–99% degradation of 2,4-D and MCPA in soil within 1 day and >99% within 3 days after inoculation with 10⁵–10⁷ herbicide-degrading bacteria g⁻¹ dry weight of soil. Enhanced degradation of MCPA was also obtained in the presence of winter wheat and white mustard without loss of the intended herbicidal effect on white mustard. The survival of an isolated MCPA-degrading Sphingomonas sp. in three realistic concentrations of formulated MCPA was very poor, showing that in practical applications direct contact between the microorganisms and the pesticide formulation must be precluded. The applicability and economic feasibility of the method and the information needed to obtain a useable product for field use are discussed.     

Transfer and expression of the herbicide-degrading plasmid pJP4 in aerobic autotrophic bacteria

Plasmid pJP4 encoding the ability to degrade the herbicide 2,4-dichlorophenoxyacetic acid (Tfd⁺) was transferred by conjugation from Escherichia coli JMP397 to various lithoautotrophic strains of Alcaligenes eutrophus and to the autotrophic bacterium Pseudomonas oxalaticus. The herbicide-degrading function of the plasmid was phenotypically expressed in all of the recipients. The majority of Tfd⁺ transconjugants also exhibited additional plasmid-encoded properties such as 3-chlorobenzoate degradation, resistance to mercuric ions, and sensitivity to the male-specific bacteriophage PR11. Furthermore, Tfd⁺ transconjugants were able to act as donors of plasmid pJP4. Physical evidence is presented by agarose gel electrophoresis showing that plasmid pJP4 coexisted with the resident plasmids widely distributed in this group of bacteria. However, in some of the hosts plasmid pJP4 was not stably maintained, had a reduced size and tended to form multimers.     

Identification of metolachlor mineralizing bacteria in aerobic and anaerobic soils using DNA-stable isotope probing

The influence of soil environmental factors such as aeration on the ecology of microorganisms involved in the mineralization and degradation of the popular soil-applied pre-emergent herbicide, metolachlor is unknown. To address this knowledge gap, we utilized DNA-based stable isotope probing (SIP) where soil microcosms were incubated aerobically or anaerobically and received herbicide treatments with unlabeled metolachlor or ¹³C-metolachlor. Mineralization of metolachlor was confirmed as noted from the evolution of ¹⁴CO₂ from ¹⁴C-metolachlor-treated microcosms and clearly demonstrated the efficient utilization of the herbicide as a carbon source. Terminal restriction fragment length polymorphisms (T-RFLP) bacterial community profiling performed on soil DNA extracts indicated that fragment 307 bp from aerobic soil and 212 bp from anaerobic soil were detected only in the herbicide-treated (both unlabeled metolachlor and ¹³C-metolachlor) soils when compared to the untreated control microcosms. T-RFLP profiles from the ultracentrifugation fractions illustrated that these individual fragments experienced an increase in relative abundance at a higher buoyant density (BD) in the labeled fractions when compared to the unlabeled herbicide amendment fractions. The shift in BD of individual T-RFLP fragments in the density-resolved fractions suggested the incorporation of ¹³C from labeled herbicide into the bacterial DNA and enabled the identification of organisms responsible for metolachlor uptake from the soil. Subsequent cloning and 16S rRNA gene sequencing of the ¹³C-enriched fractions implicated the role of organisms closely related to Bacillus spp. in aerobic mineralization and members of Acidobacteria phylum in anaerobic mineralization of metolachlor in soil.     

Degradation of glyphosate and other pesticides by ligninolytic enzymes

The ability of pure manganese peroxidase (MnP), laccase, lignin peroxidase (LiP) and horseradish peroxidase (HRP) to degrade the widely used herbicide glyphosate and other pesticides was studied in separate in vitro assays with addition of different mediators. Complete degradation of glyphosate was obtained with MnP, MnSO₄ and Tween 80, with or without H₂O₂. In the presence of MnSO₄, with or without H₂O₂, MnP also transformed the herbicide, but to a lower rate. Laccase degraded glyphosate in the presence of (a) 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS), (b) MnSO₄ and Tween 80 and (c) ABTS, MnSO₄ and Tween 80. The metabolite AMPA was detected in all cases where degradation of glyphosate occurred and was not degraded. The LiP was tested alone or with MnSO₄, Tween 80, veratryl alcohol or H₂O₂ and in the HRP assay the enzyme was added alone or with H₂O₂ in the reaction mixture. However, these enzymes did not degrade glyphosate. Further experiments using MnP together with MnSO₄ and Tween 80 showed that the enzyme was also able to degrade glyphosate in its commercial formulation Roundup^® Bio. The same enzyme mixture was tested for degradation of 22 other pesticides and degradation products present in a mixture and all the compounds were transformed, with degradation percentages ranging between 20 and 100%. Our results highlight the potential of ligninolytic enzymes to degrade pesticides. Moreover, they suggest that the formation of AMPA, the main metabolite of glyphosate degradation found in soils, can be a result of the activity of lignin-degrading enzymes.     

Biodegradation of 4-chlorobiphenyl by using induced cells and cell extract of Burkholderia xenovorans

This study aimed to evaluate the efficiency of Burkholderia xenovorans LB400 cells and their cell extract to remediate 4-chlorobiphenyl (4-CB). The bacterium previously induced with 4-CB was able to degrade up to 98% of initial 50 mg L^?1 of 4-CB from mineral medium within 96 h of incubation. The degradation of 4-CB occurred through the formation of meta-cleavage product 2-hydroxy-6-oxo-6phenylhexa-2,4-dienoic acid (HOPDA), as revealed through enzymatic assay of 2,3-dihydroxybiphenyl 1,2-dioxygenase (2,3-DHBD). A derivative of 1,2-benzenedicarboxylic acid was observed as one of the major intermediate metabolites of 4-CB degradation. Time course production of 2,3-DHBD during growth corresponds with the degradation pattern of 4-CB by the bacterium. In vitro degradation of 4-CB using cell extract of B. xenovorans showed complete degradation of initial 25 mg L^?1 of 4-CB within 6 h of incubation. To the best of the authors' knowledge, this is the first report in which in vitro degradation of 4-CB using cell extract of Burkholderia xenovorans is presented.