Isolation and characterization of 2,4-dichlorophenoxyacetic acid-catabolizing bacteria and their biodegradation efficiency in soil

Bacterial isolates (NJ 10 and NJ 15) capable of degrading the herbicide 2,4 -dichlorophenoxyacetic acid (2,4-D) were isolated from agricultural soil by enrichment culture technique. The isolates exhibited substantial growth in mineral salt medium supplemented with 0.1-0.5% of 2,4-D as a sole source o f carbon and energy. Based on their morphological, cultural and biochemical characteristics, the isolates NJ 10 and NJ 15 have been identified as Pseu domonas species and Pseudomonas aeruginosa, respectively. Biodegradation st udies in a soil microcosm enriched with pure cultures of the isolates demon strated a time-dependent disappearance of 2,4-D from the 100 mg/kg herbicid e-amended soil. The HPLC data analysis revealed 96.6 and 99.8% degradation in the soil inoculated with the pure cultures of isolates NJ 10 and NJ 15, respectively with in 20 days of incubation at 30 degrees C. Both the isolat es showed significant solubilization of inorganic phosphate [Ca-3(PO4)(2)] on the specific Pikovskaya's medium.