Department of Microbiology, Key Lab of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, Jiangsu Province, People's Republic of China.
Curr Microbiol. 2010 Sep;61(3):226-33. doi: 10.1007/s00284-010-9603-8. Epub 2010 Feb 11.
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 degrees 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.
一株能够降解百菌清（CTN）的细菌菌株 CTN-11 从中国百菌清污染土壤中分离得到。根据形态学、生化特性和 16S rRNA 基因的比较分析，菌株 CTN-11 被鉴定为食酸寡养单胞菌。菌株 CTN-11 可以在 48 小时内将 50mg/L 的 CTN 降解至无法检测的水平，并且可以在 20 到 40°C 的较宽温度范围和初始 pH 值 6.0 到 9.0 下有效降解 CTN。该新分离株与以前报道的 CTN 共代谢降解菌不同，它可以在没有其他碳源的情况下转化 CTN。从菌株 CTN-11 中克隆出一种谷胱甘肽 S-转移酶（GST）编码基因，该基因与食酸寡养单胞菌 SH35B 的基因具有 88%的序列相似性。然而，在存在谷胱甘肽的情况下，该基因没有功能表达，这表明 GST 催化的硫代取代还原脱氯不是 CTN 在 CTN-11 中的还原脱氯机制。根据串联 MS/MS 鉴定出 CTN 厌氧降解过程中产生的羟基-三氯异氰尿酸腈（CTN-OH），这证实了水解脱氯参与了 CTN 的降解。还研究了菌株 CTN-11 在无菌和非无菌土壤中对 CTN 的去除。在这两种土壤样品中，50mg/kg 的 CTN 可以在 3 天内降解至无法检测的水平。本研究突出了 CTN-11 菌株在 CTN 污染场地修复中的重要潜在用途，并提出了一种纯培养物对 CTN 的水解脱氯反应。
