Bioremediation of xenobiotic compounds including dioxins

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[1] Two kinds of bacteria, a dinenzofuran (DF)-degrader Terrabacter sp. strain DBF63 and a carbazole (CAR)-degrader Pseudomonas resinovorans strain CA10, were investigated for their ability to transform several chlorinated DFs and dibenzo-p-dioxins (DDs). It was shown that CAR 1,9a-dioxygenase from strain CA10 catalyzed angular dioxygenation of all mono- to tri-chioro-DF/DDs (CDF/CDDs) investigated in this study, but DF 4,4a-dioxygenase from strain DBF63 did not transform 2,7-diCDD. We also tried a preliminary bioremediation of the actual dioxin-contaminated soil using the soil-slurry system. The decrease of total CDD and CDF congeners by single inoculation with CA10 or DBF63 cells were 8.3 and 10%, respectively, after 7-day incubation, thus it was shown that strains CA10 and DBF63 had a potential to degrade tetra- to hepta-chlorinated congeners including the most toxic compound, 2,3,7,8-tetraCDD.[2] The fluorogenic probe assay, competitive PCR and co-extraction with internal standard cells were combined to develop a rapid, sensitive, and accurate quantification method for the copy number of a target carAa gene and the cell number of strain CA10. In addition, by using Tn5 transposon, strain CA10 was chromosomally marked with a tandem gfp gene. The real-time competitive PCR and direct counting using the GFP marker were employed to monitor the total number of carAa gene and survival of strain CA10 cells in the soil.[3] Following plate matings between CAR-degrader strain K23 and phenol-degrader strain DS1 in the presence of CAR, transconjugants able to utilize CAR were obtained. The transconjugants had large plasmid pCAR2.[4] Transgenic plants expressing DbfB fused to endoplasmic reticulum signal peptide continuously secrete recombinant proteins from their roots into a simple hydroponic medium, and the secreted DbfB proteins retained biological activity.