Abstract
A gram-negative, rod-shaped, isoproturon (IPU) utilizing bacterium was isolated from herbicide-applied wheat fields of Tarai agro-ecosystem, Pantnagar. The phylogenetic sequence analysis based on 16S rRNA sequence revealed that the isolate could be a distinct species within the genus Pseudomonas. The isolate was a close relative of Pseudoxanthomonas japonensis (95 % similarity) and designated as K2. The bacterial isolate showed positive reaction for oxidase, catalase, and 20 carbohydrates using KB009 Part A and B HiCarbohydrate™ Kit. Degradation experiments were conducted using 200 mg l−1 initial IPU as a source of carbon at different pH and temperatures. Maximum IPU degradation by K2 was observed at pH 7.0 and 30 °C, while least degradation at 6.5 pH and 25 °C. Addition of dextrose along with IPU as an auxiliary carbon source increased IPU degradation by 4.72 %, as compared to the IPU degradation without dextrose under optimum conditions. 4-isopropylaniline was detected as a degradation by-product in the medium. The present study demonstrated the IPU metabolizing capacity of a novel bacterial isolate K2 that can be a better choice for the remediation of IPU-contaminated sites.
Highlights
Isoproturon is an extensively used phenylurea herbicides for control of pre- or post-emergence broad-leaved weeds in cotton, fruits and cereal production. (Sorensen et al 2003)
A gram-negative, rod-shaped, isoproturon (IPU) utilizing bacterium was isolated from herbicide-applied wheat fields of Tarai agro-ecosystem, Pantnagar
The isolate was a close relative of Pseudoxanthomonas japonensis (95 % similarity) and designated as K2
Summary
Isoproturon is an extensively used phenylurea herbicides for control of pre- or post-emergence broad-leaved weeds in cotton, fruits and cereal production. (Sorensen et al 2003). Extensive use of IPU has been considered as a severe water pollution threat near agricultural catchments in various parts of the world, exceeding the 0.1 lg l-1 limits of European Commission (Spliid and Koppen 1998; Muller et al 2002). A variety of IPU degrading soil micro-flora has been recently isolated from contaminated sites in various parts of the world (Badawi et al 2009; Hussain et al 2009; Sun et al 2009). Addition of auxiliary carbon source in the medium or pesticide contaminated sites can stimulate microbial growth and significantly enhance the degradation rates of complex organic pollutants (Scow and Hicks 2005). In view of the facts described above, the present investigation aimed to test the IPU degradation potential of a native bacterial isolate that was recovered from IPUcontaminated field
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