Main content area

Hydrolytic Dechlorination of Chlorothalonil by Ochrobactrum sp. CTN-11 Isolated from a Chlorothalonil-Contaminated Soil

Liang, Bin, Li, Rong, Jiang, Dong, Sun, Jiquan, Qiu, Jiguo, Zhao, Yanfu, Li, Shunpeng, Jiang, Jiandong
Current microbiology 2010 v.61 no.3 pp. 226-233
Ochrobactrum anthropi, carbon, chlorothalonil, dechlorination, genes, glutathione transferase, pH, ribosomal RNA, soil, soil sampling, temperature, China
A bacterial strain, designated as CTN-11, capable of degrading chlorothalonil (CTN), was isolated from a chlorothalonil-contaminated soil in China. Based on the morphological, biochemical characteristics and comparative analysis of the 16S rRNA genes, strain CTN-11 was identified as Ochrobactrum sp. Strain CTN-11 could degrade 50 mg l⁻¹ CTN to a non-detectable level within 48 h, and efficiently degrade CTN in a relatively broad range of temperatures from 20 to 40°C and initial pH values from 6.0 to 9.0. The new isolate differed from those previously reported CTN co-metabolic degraders by transforming CTN in the absence of other carbon sources. A glutathione S-transferase (GST) coding gene, which showed 88% sequence similarity with that from Ochrobactrum anthropi SH35B, was cloned from strain CTN-11. However, the gene was not functionally expressed in the presence of glutathione, indicating that CTN was not reductively dechlorinated by thiolytic substitution catalyzed by GST in strain CTN-11. The metabolite hydroxyl-trichloroisophthalonitrile (CTN-OH) produced during CTN anaerobic degradation was identified based on tandem MS/MS, confirming that hydrolytic dechlorination was involved in the CTN degradation. The removal of CTN by strain CTN-11 in sterile and non-sterile soils was also studied. In both soil samples, 50 mg kg⁻¹ CTN could be degraded to an undetectable level within 3 days. This study highlights an important potential use of strain CTN-11 for the cleanup of CTN-contaminated sites and presents a hydrolytic dechlorination reaction of CTN by a pure culture.