Maintenance and conjugative transfer of dioxin catabolic plasmids in a Rhodococcus sp.

Abstract:

[Objective] To examine the stable maintenance and conjugative transfer of the dioxin-catabolic plasmids pDF01 (170 kb) and pDF02 (242 kb) harbored by Rhodococcus sp. strain p52. [Methods] We monitored the presence of pDF01 and pDF02 in strain p52 during continuous transfer in LB medium. We also performed mating experiments using strain p52 as a donor and bacterial strains belonging to different genera as recipients, and confirmed the transconjugant by colony hybridization and Southern hybridization. Further, we examined the function of catabolic genes in a transconjugant by degrading test. [Results] Both pDF01 and pDF02 could maintain in strain p52 after continuous transfer in LB medium less than 47 times, but pDF01 was lost after 65 times transfer in LB medium. Plasmid pDF01 and pDF02 could transfer concomitantly from strain p52 to the recipient strains, such as Rhodococcus rhodochrous, Rhodococcus erythropolis, Janibacter terrae and Arthrobacter sp., while Arthrobacter sp. showed the highest transconjugation frequency of 3.5×10?6 colonies per recipient. The results of Southern hybridization confirmed that Arthrobacter sp. transconjugant obtained pDF01 and pDF02. Furthermore, the catabolic plasmids could function in Arthrobacter sp. transconjugant, which could use dibenzofuran for growth comparing with the donor strain p52. [Conclusion] The dioxin-degrader Rhodococcus sp. strain p52 has potential for genetic bioaugmentation in contaminated environments.