School of Biology and Environmental Science, Ardmore House, University College Dublin, Dublin, Ireland.
FEMS Microbiol Ecol. 2010 Aug;73(2):363-9. doi: 10.1111/j.1574-6941.2010.00906.x. Epub 2010 May 10.
The tfdC and C23O genes encode two catechol dioxygenases that catalyse ortho and meta cleavage of a key metabolite (chlorocatechol) of 2,4-dichlorophenol (2,4-DCP) metabolism, respectively. Primers were designed and a real-time PCR assay was developed to assess the abundance and expression of both tfdC and C23O genes in a soil amended with 2,4-DCP over a 21-day period. tfdC, the gene encoding the ortho cleaving dioxygenase, was significantly more abundant than the meta cleaving dioxygenase gene (C23O) throughout the experiment. The highest levels of tfdC were observed 2 days after amendment of soil with 2,4-DCP, at which stage the rate of 2,4-DCP degradation was at its maximum. In contrast, C230 copy numbers declined initially and peaked when degradation had slowed considerably. mRNA of the two chlorocatechol dioxygenase genes was not detected on day 0, but both genes were expressed after this time point. tfdC was expressed at a significantly higher level than C23O in 2,4-DCP-amended soil throughout the course of the microcosm, indicating the dominance of the ortho metabolic pathway. Phylogenetic analysis revealed a wide diversity of chlorocatechol dioxygenase genes in the 2,4-DCP-exposed soil examined.
tfdC 和 C23O 基因分别编码两种儿茶酚 1,2-双加氧酶，分别催化 2,4-二氯苯酚（2,4-DCP）代谢中的关键代谢物（邻氯儿茶酚）的邻位和间位裂解。设计了引物，并开发了实时 PCR 检测法，以评估在添加 2,4-DCP 的土壤中 21 天内 tfdC 和 C23O 基因的丰度和表达。在整个实验过程中，编码邻位裂解双加氧酶的 tfdC 基因的丰度明显高于间位裂解双加氧酶基因（C23O）。在添加 2,4-DCP 2 天后，tfdC 达到最高水平，此时 2,4-DCP 降解率达到最大值。相比之下，C230 的拷贝数最初下降，当降解速度明显减慢时达到峰值。在第 0 天未检测到两种氯代儿茶酚双加氧酶基因的 mRNA，但在此时间点之后，这两个基因均有表达。在 2,4-DCP 处理的土壤中，tfdC 的表达水平始终显著高于 C23O，表明邻位代谢途径占主导地位。系统发育分析显示，在受 2,4-DCP 暴露的土壤中，存在广泛的儿茶酚 1,2-双加氧酶基因多样性。
