Degradation of Bromoxynil in Regina Heavy Clay*

Smith, Allan E.

doi:10.1111/j.1365-3180.1971.tb01010.x

Cited by 34 publications

(14 citation statements)

References 6 publications

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“…7 days at both 10 and 50 mg kg −1 concentrations (Fig. 1a,b) the contributions of abiotic factors, such as volatilization, were essentially negligible, which is consistent with previous reports (Smith 1971; Smith and Cullimore 1974). In contrast, subsequent applications, every 28 days, had significantly different effects on degradation kinetics.…”

Section: Discussionsupporting

confidence: 92%

The degradation of the herbicide bromoxynil and its impact on bacterial diversity in a top soil

Baxter

Cummings

2008

J Appl Microbiol

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Aims: To study how repeated applications of an herbicide bromoxynil to a soil, mimicking the regime used in the field, affected the degradation of the compound and whether such affects were reflected by changes in the indigenous bacterial community present. Methods and Results: Bromoxynil degradation was monitored in soil microcosms using HPLC. Its impact on the bacterial community was determined using denaturing gradient gel electrophoresis (DGGE) and quantitative PCR of five bacterial taxa (Pseudomonads, Actinobacteria, α‐Proteobacteria, Acidobacteria and nitrifying bacteria). Three applications of 10 mg kg−1 of bromoxynil at 28‐day intervals resulted in rapid degradation, the time for removal of 50% of the compound decreasing from 6·4 days on the first application to 4·9 days by the third. Bacterial population profiles showed significant similarity throughout the experiment. With the addition of 50 mg kg−1 bromoxynil to soil, the degradation was preceded by a lag phase and the time for 50% of the compound to be degraded increased from 7 days to 28 days by the third application. The bacterial population showed significant differences 7 days after the final application of bromoxynil that correlated with an inhibition of degradation during the same period. Conclusions: These analyses highlighted that the addition of bromoxynil gave rise to significant shifts in the community diversity and its structure as measured by four abundant taxa, when compared with the control microcosm. These changes persisted even after bromoxynil had been degraded. Significance and Impact of the Study: Here we show that bromoxynil can exert an inhibitory effect on the bacterial population that results in decreased rates of degradation and increased persistence of the compound. In addition, we demonstrate that molecular approaches can identify statistically significant changes in microbial communities that occur in conjunction with changes in the rate of degradation of the compound in the soil.

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Section: Discussionsupporting

confidence: 92%

The degradation of the herbicide bromoxynil and its impact on bacterial diversity in a top soil

Baxter

Cummings

2008

J Appl Microbiol

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“…Of these organisms F. solani was a more effective degrader of the herbicide than was the bacterium. It seems likely that hydrolysis of the nitrile group is the limiting factor in the degradation of nitrilic herbicides and that the comparative persistence of Dichlobenil in the environment (Verloop, 1972) compared with the rapid disappearance of Bromoxynil and loxynil (Carpenter et al, 1964;Smith, 1971) simply reflects the invulnerability of ortho-substituted nitriles to attack by fungal, plant and bacterial nitrilases compared with the ready hydrolysis of most meta-and para-substituted compounds by both the fungal and plant enzymes. I acknowledge the skilled technical assistance of Mr. R. Stevenson.…”

Section: Effect Of Inhibitors and Metal Ionsmentioning

confidence: 98%

Fungal degradation of aromatic nitriles. Enzymology of C-N cleavage by Fusarium solani

Harper

1977

Biochemical Journal

144

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1. A strain of the fungus Fusarium solani able to use benzonitrile as sole source of carbon and nitrogen was isolated by elective culture. 2. Respiration studies indicate that the nitrile, after degradation to benzoate, is catabolized via catechol or alternatively via p-hydroxybenzoate and 3,4-dihydroxybenzoate. 3. Cell-free extracts of benzonitrile-grown cells contain an enzyme mediating the conversion of benzonitrile into benzoate and ammonia. 4. The nitrilase enzyme was purified by DEAE-cellulose chromatography, (NH(4))(2)SO(4) precipitation and gel filtration on Sephadex G-200. The homogeneity of the purified enzyme preparation was confirmed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and isoelectric focusing on polyacrylamide gel. 5. The enzyme showed a broad pH optimum between pH7.8 and 9.1 and a K(m) with benzonitrile as substrate of 0.039mm. The activation energy of the reaction deduced from an Arrhenius plot was 48.4kJ/mol. 6. The enzyme was susceptible to inhibition by thiol-specific reagents and certain heavy metal ions. 7. Gel filtration gave a value of 620000 for the molecular weight of the intact enzyme. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis demonstrated that the enzyme was composed of eight subunits of mol.wt. 76000. 8. Rates of enzymic attack on various substrates indicated that the nitrilase has a fairly broad specificity and that the fungus probably plays an important role in the biodegradation of certain nitrilic herbicides in the environment.

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“…However, one could hypothesize that ioxynil is subject to a similar pathway (also retaining the halogens) because of the structural similarity of these two herbicides. The most commonly reported aerobic bromoxynil transformation products are 3,5-dibromo-4-hydroxybenzamide and 3,5-dibromo-4-hydroxybenzoate (DBHB) (15,16,27,37,42,43,47,48). DBHB can be formed directly from the parent (27) or via 5-dibromo-4-hydroxybenzamide (15,43,48).…”

mentioning

confidence: 99%

Dehalogenation of the Herbicides Bromoxynil (3,5-Dibromo-4-Hydroxybenzonitrile) and Ioxynil (3,5-Diiodino-4-Hydroxybenzonitrile) by Desulfitobacterium chlororespirans

Cupples

Sanford

Sims

2005

Appl Environ Microbiol

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Desulfitobacterium chlororespirans has been shown to grow by coupling the oxidation of lactate to the metabolic reductive dehalogenation of ortho chlorines on polysubstituted phenols. Here, we examine the ability of D. chlororespirans to debrominate and deiodinate the polysubstituted herbicides bromoxynil (3,5-dibromo-4-hydroxybenzonitrile), ioxynil (3,5-diiodo-4-hydroxybenzonitrile), and the bromoxynil metabolite 3,5-dibromo-4-hydroxybenzoate (DBHB). Stoichiometric debromination of bromoxynil to 4-cyanophenol and DBHB to 4-hydroxybenzoate occurred. Further, bromoxynil (35 to 75 M) and DBHB (250 to 260 M) were used as electron acceptors for growth. Doubling times for growth (means ؎ standard deviations for triplicate cultures) on bromoxynil (18.4 ؎ 5.2 h) and DBHB (11.9 ؎ 1.4 h), determined by rate of [ 14 C]lactate uptake into biomass, were similar to those previously reported for this microorganism during growth on pyruvate (15.4 h). In contrast, ioxynil was not deiodinated when added alone or when added with bromoxynil; however, ioxynil dehalogenation, with stoichiometric conversion to 4-cyanophenol, was observed when the culture was amended with 3-chloro-4-hydroxybenzoate (a previously reported electron acceptor). To our knowledge, this is the first direct report of deiodination by a bacterium in the Desulfitobacterium genus and the first report of an anaerobic pure culture with the ability to transform bromoxynil or ioxynil. This research provides valuable insights into the substrate range of D. chlororespirans.An increasingly popular approach for the remediation of halogenated environmental pollutants is biological reductive dehalogenation. Dechlorination is the most commonly reported reductive dehalogenation process, due to the widespread pollution of chlorinated compounds (e.g., tetrachloroethene, trichloroethene, or chlorinated phenols), with few reports on the reduction of other halogens. However, the expanding list of emerging halogenated contaminants, including polybrominated fire retardants (20), disinfection by-products (32), perfluorinated surfactants (5), and pesticides (9, 26), illustrates the need for a greater understanding of defluorination, debromination, and deiodination. To address this, the unexploited potential of previously isolated chlororespiring microorganisms is of particular interest.Bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) is used for the postemergence control of annual broad-leaved weeds in cereals, maize, sorghum, flax, allium species, mint, and grass seed crops (35) (Fig. 1). The octanoate ester of bromoxynil (3,5-dibromo-4-cyanophenyl octanoate), also an herbicide, is readily degraded in nonsterile water and in other biological systems to bromoxynil (35). Ioxynil (3,5-diiodo-4-hydroxybenzonitrile) (Fig. 1) is used for the postemergence control of annual broad-leaved weeds in cereals, onions, leeks, shallots, flax, sugar cane, forage grasses, lawns, and turf (35).

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Degradation of Bromoxynil in Regina Heavy Clay*

Cited by 34 publications

References 6 publications

The degradation of the herbicide bromoxynil and its impact on bacterial diversity in a top soil

The degradation of the herbicide bromoxynil and its impact on bacterial diversity in a top soil

Fungal degradation of aromatic nitriles. Enzymology of C-N cleavage by Fusarium solani

Dehalogenation of the Herbicides Bromoxynil (3,5-Dibromo-4-Hydroxybenzonitrile) and Ioxynil (3,5-Diiodino-4-Hydroxybenzonitrile) by Desulfitobacterium chlororespirans

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