Affiliation:
1. Horticulture
Research International, Wellesbourne, Warwick CV35
9EF
2. Department of
Biological Sciences, Imperial College at Silwood Park, Ascot,
Berkshire SL5 7PY, United
Kingdom
Abstract
ABSTRACT
Repeated
treatment with fenamiphos (ethyl 4-methylthio-
m
-tolyl
isopropylphosphoramidate) resulted in enhanced biodegradation of this
nematicide in two United Kingdom soils with a high pH (≥7.7).
In contrast, degradation of fenamiphos was slow in three acidic United
Kingdom soils (pH 4.7 to 6.7), and repeated treatments did not result
in enhanced biodegradation. Rapid degradation of fenamiphos was
observed in two Australian soils (pH 6.7 to 6.8) in which it was no
longer biologically active against plant nematodes. Enhanced degrading
capability was readily transferred from Australian soil to United
Kingdom soils, but only those with a high pH were able to maintain this
capability for extended periods of time. This result was confirmed by
fingerprinting bacterial communities by 16S rRNA gene profiling of
extracted DNA. Only United Kingdom soils with a high pH retained
bacterial DNA bands originating from the fenamiphos-degrading
Australian soil. A degrading consortium was enriched from the
Australian soil that utilized fenamiphos as a sole source of carbon.
The 16S rRNA banding pattern (determined by denaturing gradient gel
electrophoresis) from the isolated consortium migrated to the same
position as the bands from the Australian soil and those from the
enhanced United Kingdom soils in which the Australian soil had been
added. When the bands from the consortium and the soil were sequenced
and compared they showed between 97 and 100% sequence identity,
confirming that these groups of bacteria were involved in degrading
fenamiphos in the soils. The sequences obtained showed similarity to
those from the genera
Pseudomonas
,
Flavobacterium
,
and
Caulobacter
. In the Australian soils, two different
degradative pathways operated simultaneously: fenamiphos was converted
to fenamiphos sulfoxide (FSO), which was hydrolyzed to the
corresponding phenol (FSO-OH) or was hydrolyzed directly to fenamiphos
phenol. In the United Kingdom soils in which enhanced degradation had
been induced, fenamiphos was oxidized to FSO and then hydrolyzed to
FSO-OH, but direct conversion to fenamiphos phenol did not
occur.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
82 articles.
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