Isolation and Characterization of 2,4-Dichlorophenoxyacetic Acid Degrading Organisms from Soil in Jordan Valley

2,4-Dichlorophenoxyacetic acid (2,4-D) degrading bacteria were isolated from soil samples collected from selected sites in Jordan Valley, which had a history of 2,4-D exposure. The herbicide 2,4-D was used in aminimal salt medium as a sole source of carbon to isolate and enumerate the 2,4-D-degraders by most probable – number (MPN) method. One site have previous history of exposure to 2,4-D found to contain 88 2,4-D-degraders/g soil suspension; other sites were not exposed to 2,4-D and showed much lower numbers of 2,4-D-degraders ranging from 0.5-2.1 degraders/g soil suspension. One of the 7 isolates was found to degrade 2,4-D entirely in 45 h and it was the most potent isolate. It was identified and found to be Pseudomonas putida. It grew and degraded 500 ppm of 2,4-D optimally at pH 6.5 and 30°C.