Isolation and characterization of an atrazine-degrading Rhodococcus sp. strain MB-P1 from contaminated soil.

AIMS: The aim of this study is to isolate and characterize organisms capable of utilizing high concentration atrazine from the contaminated sites.

METHODS AND RESULTS: A selective enrichment was used for isolating atrazine-degrading organisms from the contaminated sites resulting in isolation of an efficient atrazine-degrading organism designated as strain MB-P1. On the basis of 16S rRNA gene sequencing, total cellular fatty acid analysis and physiological and biochemical tests, strain MB-P1 was identified as a member of genus Rhodococcus. High performance liquid chromatography was performed to identify the atrazine degradation intermediates demonstrating that the degradation proceeds via formation of 'de-ethylatrazine' and 'de-isopropylatrazine'. Further, plasmid curing by SDS method showed atrazine-degrading gene(s) to be plasmid-encoded.

CONCLUSIONS: We have successfully isolated a Rhodococcus sp. strain MB-P1 which is capable of utilizing atrazine as sole source of carbon and energy at very high concentrations of 1000 ppm. The pathway for degradation of atrazine has also been determined. The metabolic gene(s) responsible for atrazine degradation was found to be plasmid-encoded.

SIGNIFICANCE AND IMPACT OF THE STUDY: Rhodococcus sp. strain MB-P1 could be used as an ideal model system for in-situ degradation and restoration of ecological niches which are heavily contaminated with atrazine.