We isolated a novel aerobic dieldrin-degrading bacterium from an enrichment culture in a soil-charcoal perfusion system. Enrichment culture using a soil-charcoal perfusion system was an effective way to obtain microorganisms that degrade recalcitrant compounds. The soil-charcoal perfusion was performed using aldrin trans-diol, which was a metabolite of dieldrin. Aldrin trans-diol had higher bioavailability (2.5 mg/l) than dieldrin (0.1-0.25 mg/l), therefore it is possible for microorganisms to utilize it as a substrate in soil. After 100 days of circulation and three exchanges of the medium, the enriched charcoal was harvested and a bacterium isolated. The isolate was designated as strain KSF27 and was found to be closely related to Pseudonocardia spp. as determined by 16S rRNA sequencing analysis. Strain KSF27 degraded aldrin trans-diol by 0.05 mu mol/l from an initial concentration of 25.5 mu mol/l. The metabolite of aldrin trans-diol was detected by HPLC/MS and determined to be aldrindicarboxylic acid based on retention time and the MS fragment. Moreover, strain KSF27 degraded dieldrin from 14.06 mu mol/l to 2.01 mu mol/l over a 10-day incubation at 30 degrees C. This strain degraded dieldrin and other persistent organo-chlorine pesticides, such as alpha-endosulfan, beta-endosulfan, endosulfan sulfate, heptachlor, heptachlor epoxide and chlordecone. (C) 2011 Elsevier Inc. All rights reserved.