Biodegradation of Methoxychlor and Its Metabolites by the White Rot Fungus Stereum hirsutum Related to the Inactivation of Estrogenic Activity

The white rot fungus Stereum hirsutum was used to degrade methoxychlor [2,2,2-trichloro-1,1-bis(4-methoxyphenyl)ethane] in culture and the degraded products were extensively determined. The estrogenic activity of the degraded products of methoxychlor was examined using cell proliferation and pS2 gene expression assays in MCF-7 cells. S. hirsutum showed high resistance to methoxychlor 100 ppm, and the mycelial growth was fully completed within 8 days of incubation at 30°C. Methoxychlor in liquid culture medium was gradually converted into 2,2-dichloro-1,1-bis(4-methoxyphenyl)ethane, 2,2-dichloro-1,1-bis(4-methoxyphenyl)ethylene, 2-chloro-1,1-bis(4-methoxyphenyl) ethane, 2-chloro-1,1-bis(4-methoxyphenyl) ethylene, and 1,1-bis(4-methoxyphenyl)ethylene, indicating that methoxychlor is dominantly degraded by dechlorination and dehydrogenation. MCF-7 cells were demonstrated to proliferate actively at the 10^?5 M concentration of methoxychlor. However, cell proliferation was significantly inhibited by the incubation with methoxychlor culture media containing S. hirsutum. In addition, the expression level of pS2 mRNA was increased at the concentration (10^?5 M) of methoxychlor. The reductive effect of S. hirsutum for methoxychlor was clear but not significant as in the proliferation assay.     

The fate of methoxychlor in soils and transformation by soil microorganisms

Abstract

Methoxychlor was found to be sufficiently persistant in soil and its residues were present even 18 months after the soil treatment. Saprophytes, fungi and actinomyces were unaffected by varying concentrations of methoxychlor, azotobacter however was susceptable. Soil strains isolated did not utilize methoxychlor as a sole carbon source except for 9 cultures belonging to the genera Bacillus, Acineto‐bacter and Rhodococcus which carried out the complete dechlorination, demethylation and splitting of one of methoxychlor aromatic rings. Anaerobic conditions were more favorable for methoxychlor biodegradation by soil and pure microbial cultures.     

The persistence and disappearance by washoff and dryfall of methoxychlor from soybean foliage—a preliminary study

Abstract

The persistence and disappearance (washoff or dryfall) of methoxychlor [2,2‐bis(p‐methoxypheny1)‐1,1,1‐trichloroethane] from mature soybean [Glycine max (L.) Merrill] foliage was investigated in a small field plot study under natural rainfall conditions in 1977 and 1978. Residue analyses were conducted using whole plant samples‐ Methoxychlor washoff rate was 8±4% of the amount on plants (prior to rain) per centimeter of rainfall, regardless of time after application. Total seasonal washoff for 1978 accounted for 33.5% of the applied pesticide; however, 30.5% of the total loss was removed by washoff on the second day after application. Dryfall or dislodgeable residue accounted for less than 1% of the amount applied. The amount of dryfall was significantly greater in plots entered by workers than in those where entry was avoided. More than 19% of the applied methoxychlor was lost as a result of through‐fall to the ground during application to the plots. Statistical analyses indicated that within‐sample variation for mechanical chopping of plant samples was significantly smaller at the 5% level than for a hand chopping method. Results from this study will be useful in defining research objectives for the development of algorithms to describe the behavior of foliar‐applied compounds. Such algorithms are necessary for estimating runoff losses of insecticides to water bodies.