Degradation, pesticides

The rate and extent of pesticide metaboHsm can vary dramatically, depending on chemical stmcture, the number of specific pesticide-degrading microorganisms present and their affinity for the pesticide, and environmental parameters. The extent of metaboHsm can vary from relatively minor transformations which do not significantly alter the chemical or toxicological properties of the pesticide, to mineralisation, ie, degradation to CO2, H2O, NH" 4, Cf, etc. The rate of metaboHsm can vary from extremely slow (half-life of years) to rapid (half-life of days). 

For those pesticides that are cometabolized, ie, not utilized as a growth substrate, the assumption of first-order kinetics is appropriate. The more accurate kinetic expression is actually pseudo-first-order kinetics, where the rate is dependent on both the pesticide concentration and the numbers of pesticide-degrading microorganisms. However, because of the difficulties in enumerating pesticide-transforming microorganisms, first-order rate constants, or half-hves, are typically reported. Based on kinetic constants, it is possible to rank the relative persistence of pesticides. Pesticides with half-hves of <10 days are considered to be relatively nonpersistent pesticides with half-hves of >100 days are considered to be relatively persistent. 

Somara S, Siddavattam D. 1995. Plasmid mediated organophosphate pesticide degradation by Flavobactrium balustinum. Biochem Molec Biol Int 36 627-631. 

Hodapp DM, Winterlin W. 1989. Pesticide degradation in model soil evaporation beds. Bull Environ Contam Toxicol 43 36-44. 

Pesticide Degradation Laboratory, AEQI, USDA, SEA-AR, Beltsville, MD 20705... 

Shao ZQ, R Behki (1996) Characterization of the expression of the thcB gene, coding for a pesticide-degrading cytochrome P450 in Rhodococcus strains. Appl Environ Microbiol 62 403-407. 

Little information has been published on pesticide degradation products, produced in coffee, that may have significant physiological effects. Some information has been published, however, for glyphosate,191 aldicarb,194 and carbofuran,187 although there is some controversy surrounding the carbofuran data.188... 

Matsumura, F. 1978. Mechanisms of Pesticide Degradation. U.S.Environ. Protection Agency Rep. 600/1-78-065. 43 pp. 

In conclusion, the flavoprotein systems isolated from the algae and the bacteria, have a good potential to play significant roles in pesticide degradation in aquatic environments. Such flavoprotein systems are active in degradation of xenobiotics both under aerobic and anaerobic conditions by promoting photochemical and reductive reactions. 

Goring CA, Laskowski DA, Hamaker JW, et al. 1975. Principles of pesticide degradation in soil. In Hague R, Freed VH, ed. Environmental dynamics of pesticides. New York, NY Plenum Press, 135-172. 

Camper, N.D. Effects of pesticide degradation products on soil microflora, in Pesticide Transformation Products. Fate and Significance in the Environment, ACS Symposium Series 429, Somasundaram, L. and Coats, J.R., Eds. (New York American Chemical Society, 1991), pp. 205-216. 

Doyle. R.C..Kaufman, D.D., and Burt. G.W. Effect of dairy manure and sewage sludge on C-pesticide degradation in soil, J. Agric. Food Chem., 26 987-989,1978. 

Hildebrandt A, Lacorte S, Barcelo D (2007) Assessment of priority pesticides, degradation products, and pesticide adjuvants in groundwaters and top soils from agricultural areas of the Ebro river basin. Anal Bioanal Chem 387 1459-1468... 

The effects of all combinations of aeration and nutrients are easily discernable on the right hand YES count column. The increase from 10 to 14 degradation units on a scale of 0 to 32 when aeration was incorporated must be weighed carefully against the cost of adding aeration to the containers. Nutrients had an inhibitory, if any, effect on pesticide degradation in general. 

On a scale of 0 to 64, the individual pesticide degradations decreased from 31 to 14 when mixtures were present. This apparent antagonistic action of mixtures was probably more of a latency effect related to the six-fold increase in total pesticide concentrations rather than a toxic action to the microorganisms. 

Many pesticides degrade to polar products that form organic anions in a water matrix. These are sometimes missed due to the difficulty in extracting trace amounts of the ionic material from a water matrix. A recently developed anion exchange procedure for isolating acidic compounds from dilute aqueous solutions (10-12) was used for recovering the anionic material from liquid samples collected from the two pits. 

Chakrabarty has extensively reviewed the biodegradation of pesticides (J ). Table I shows the results of several studies on the enzymatic activity of microbial cell-free extracts for pesticide degradation. Clearly, there is substantial evidence to suggest that enzymes might be used in the development of biotechnology for use in degradation of pesticides. 

Table I. Enzymatic Activity of Microbial Cell-Free Extracts For Pesticide Degradation...

We have accumulated some experimental evidence for the involvement of iron-sulfur proteins in pesticide degradation and now present the data. 

These observations suggest that the oxidative reactions occurring on toxaphene are similar in nature to the system described for camphor degradation (M). It is unfortunate that the above experiments could only be conducted with washed intact cells as cell-free preparations in all cases did not exhibit metabolic capabilities. The reason for this phenomenon has not been found, but to our knowledge no other research group has been able to demonstrate pesticide degrading activities of such oxygenase systems in cell-free preparations. 

An effort was made to investigate the involvement of cell-free extracts of a bacterial mixed-function oxidase ystem in pesticide degradation. In this experiment, the degradation of C-mexacarbate was examined using the 10,000 g supernatant of lysozyme-treated B. megaterium cells in 0.03 M phosphate buffer at pH 7.0, Incubation was... 

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