Department of Civil and Environmental Engineering, Rice University, Houston, Texas, United States.
Environ Sci Technol. 2013 Sep 3;47(17):9950-8. doi: 10.1021/es402228x. Epub 2013 Aug 16.
Soluble di-iron monooxygenases (SDIMOs), especially group-5 SDIMOs (i.e., tetrahydrofuran and propane monooxygenases), are of significant interest due to their potential role in the initiation of 1,4-dioxane (dioxane) degradation. Functional gene array (i.e., GeoChip) analysis of Arctic groundwater exposed to dioxane since 1980s revealed that various dioxane-degrading SDIMO genes were widespread, and PCR-DGGE analysis showed that group-5 SDIMOs were present in every tested sample, including background groundwater with no known dioxane exposure history. A group-5 thmA-like gene was enriched (2.4-fold over background, p < 0.05) in source-zone samples with higher dioxane concentrations, suggesting selective pressure by dioxane. Microcosm assays with (14)C-labeled dioxane showed that the highest mineralization capacity (6.4 ± 0.1% (14)CO2 recovery during 15 days, representing over 60% of the amount degraded) corresponded to the source area, which was presumably more acclimated and contained a higher abundance of SDIMO genes. Dioxane mineralization ceased after 7 days and was resumed by adding acetate (0.24 mM) as an auxiliary substrate to replenish NADH, a key coenzyme for the functioning of monoxygenases. Acetylene inactivation tests further corroborated the vital role of monooxygenases in dioxane degradation. This is the first report of the prevalence of oxygenase genes that are likely involved in dioxane degradation and suggests their usefulness as biomarkers of dioxane natural attenuation.
可溶性二铁单加氧酶（SDIMO），特别是第 5 组 SDIMO（即四氢呋喃和丙烷单加氧酶），由于其在 1,4-二恶烷（二恶烷）降解起始中的潜在作用而备受关注。对自 20 世纪 80 年代以来暴露于二恶烷的北极地下水进行的功能基因阵列（即 GeoChip）分析表明，各种二恶烷降解 SDIMO 基因广泛存在，而 PCR-DGGE 分析表明，第 5 组 SDIMO 存在于每个测试样本中，包括没有已知二恶烷暴露史的背景地下水。在二恶烷浓度较高的源区样品中，thmA 样基因得到了富集（比背景高 2.4 倍，p < 0.05），这表明二恶烷存在选择压力。用（14）C 标记的二恶烷进行的微宇宙实验表明，最高的矿化能力（15 天内 6.4 ± 0.1%（14）CO2 回收率，代表降解量的 60%以上）与源区相对应，该区域可能更适应环境，并且含有更高丰度的 SDIMO 基因。在 7 天后，二恶烷矿化停止，通过添加作为辅助底物的乙酸盐（0.24 mM）来补充 NADH，恢复了单加氧酶功能的关键辅酶，矿化得以恢复。乙炔失活试验进一步证实了单加氧酶在二恶烷降解中的重要作用。这是首次报道可能参与二恶烷降解的加氧酶基因的普遍性，并表明它们可用作二恶烷自然衰减的生物标志物。
