Plasmid diversity within a 2,4-dichlorophenoxyacetic acid-degrading Variovorax paradoxus population isolated from a contaminated soil

Thirty-two 2,4-dichlorophenoxyacetic acid (2,4-D)-degrading (Tfd(+)) isolates of Variovorax paradoxus were obtained from a sample of contaminated soil by enrichment culture and were divided into six groups based on the size and number of plasmids they contained. Isolates within each of the six groups had identical and unique plasmid profiles consisting of multiple plasmids of diverse size. Curing of plasmids resulted in loss of ability to degrade 2,4-D. EcoR1 restriction patterns of plasmids contained by Tfd(+) and Tfd(-) clones suggested that the plasmids did not derive from a common origin, since patterns revealed unique differences as well as similarities in restriction fragment size. In addition, the data suggest that in situ gene transfer and recombination events occurred frequently within this population.