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Applied and Environmental Microbiology, July 2000, p. 2822-2828, Vol. 66, No. 7
CSIRO Entomology, Canberra ACT 2601, Australia
Received 3 February 2000/Accepted 2 May 2000
An endosulfan-degrading mixed bacterial culture was enriched from
soil with a history of endosulfan exposure. Enrichment was obtained by
using the insecticide as the sole source of sulfur. Chemical hydrolysis
was minimized by using strongly buffered culture medium (pH 6.6), and
the detergent Tween 80 was included to emulsify the insecticide,
thereby increasing the amount of endosulfan in contact with the
bacteria. No growth occurred in control cultures in the absence of
endosulfan. Degradation of the insecticide occurred concomitant with
bacterial growth. The compound was both oxidized and hydrolyzed. The
oxidation reaction favored the alpha isomer and produced
endosulfate, a terminal pathway product. Hydrolysis involved a novel
intermediate, tentatively identified as endosulfan monoaldehyde on the
basis of gas chromatography-mass spectrometry and chemical
derivatization results. The accumulation and decline of metabolites
suggest that the parent compound was hydrolyzed to the putative
monoaldehyde, thereby releasing the sulfite moiety required for growth.
The monoaldehyde was then oxidized to endosulfan hydroxyether and
further metabolized to (a) polar product(s). The cytochrome P450
inhibitor, piperonyl butoxide, did not prevent endosulfan oxidation or
the formation of other metabolites. These results suggest that this
mixed culture is worth investigating as a source of
endosulfan-hydrolyzing enzymes for use in enzymatic bioremediation of
endosulfan residues.
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Enrichment of an Endosulfan-Degrading Mixed Bacterial
Culture
*
Corresponding author. Mailing address: CSIRO
Entomology, GPO Box 1700, Canberra ACT 2601, Australia. Phone: 61 2 6246 4157. Fax: 61 2 6246 4173. E-mail:
Tara.Sutherland{at}ento.csiro.au.
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