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Appl. Environ. Microbiol. doi:10.1128/AEM.02687-07
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Rapid mineralization of the phenylurea herbicide diuron by Variovorax sp. SRS16 in pure culture and within a two-member consortium

Department of Geochemistry, Geological Survey of Denmark and Greenland (GEUS), ster Voldgade 10, DK-1350 Copenhagen K, Denmark

^* To whom correspondence should be addressed. Email: srs{at}geus.dk.

	Abstract

The phenylurea herbicide diuron (N-(3,4-dichlorophenyl)-N,N-dimethylurea) is widely used in a broad range of herbicide formulations and as a consequence it is frequently detected as a major water contaminant in areas with extensive use. We constructed a linuron (N-(3,4-dichloro-phenyl)-N-methoxy-N-methylurea) and diuron mineralizing two-member consortium by combining the cooperative degradation capacities of the diuron-degrading Arthrobacter globiformis strain D47 with the linuron-mineralizing Variovorax sp. SRS16. Neither of the strains performed diuron mineralization alone in a mineral medium but combined they mineralized 31 – 62% of the added [ring-U-¹⁴C]diuron to ¹⁴CO₂, depending on the initial diuron concentrations and the cultivation conditions. The constructed consortium was used to initiate the degradation and mineralization of diuron in soil without a natural attenuation potential. This approach led to the unexpected finding that Variovorax sp. SRS16 was able to mineralize diuron in pure culture when supplemented with appropriate growth substrates, making it the first known bacterium capable of mineralizing diuron and representatives of both N,N-dimethyl- and N-methoxy-N-methyl-substituted phenylurea herbicides. The ability of the coculture to mineralize µg l^-1 levels of diuron was compared to strain SRS16 alone, revealing a superior extent of mineralization by the two-member consortium, with 31 – 33% of the added [ring-U-¹⁴C]diuron mineralized to ¹⁴CO₂ at 15.5 – 38.9 µg l^-1 diuron. These results suggest that the consortium consisting of strains SRS16 and D47 could be a promising candidate for remediation of soils and waters contaminated with diuron, linuron and their shared metabolite 3,4-dichloroaniline.