Isolation and characterization of an isoproturon mineralizing <Emphasis Type="Italic">Sphingomonas</Emphasis> sp. strain SH from a French agricultural soil |
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Authors: | Sabir Hussain Marion Devers-Lamrani Najoi El Azhari Fabrice Martin-Laurent |
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Institution: | 1.UMR Microbiologie du Sol et de l’Environment,INRA-Université de Bourgogne,Dijon Cedex,France;2.Welience Agro-Environnement,Dijon Cedex,France |
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Abstract: | The phenylurea herbicide isoproturon, 3-(4-isopropylphenyl)-1,1-dimethylurea (IPU), was found to be rapidly mineralized in
an agricultural soil in France that had been periodically exposed to IPU. Enrichment cultures from samples of this soil isolated
a bacterial strain able to mineralize IPU. 16S rRNA sequence analysis showed that this strain belonged to the phylogeny of
the genus Sphingomonas (96% similarity with Sphingomonas sp. JEM-14, AB219361) and was designated Sphingomonas sp. strain SH. From this strain, a partial sequence of a 1,2-dioxygenase (catA) gene coding for an enzyme degrading catechol putatively formed during IPU mineralization was amplified. Phylogenetic analysis
revealed that the catA sequence was related to Sphingomonas spp. and showed a lack of congruence between the catA and 16S rRNA based phylogenies, implying horizontal gene transfer of the catA gene cluster between soil microbiota. The IPU degrading ability of strain SH was strongly influenced by pH with maximum degradation
taking place at pH 7.5. SH was only able to mineralize IPU and its known metabolites including 4-isopropylaniline and it could
not degrade other structurally related phenylurea herbicides such as diuron, linuron, monolinuron and chlorotoluron or their
aniline derivatives. These observations suggest that the catabolic abilities of the strain SH are highly specific to the metabolism
of IPU. |
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