Beller Harry R
Lawrence Livermore National Laboratory, CA 94551-0808, USA.
Water Res. 2002 May;36(10):2533-40. doi: 10.1016/s0043-1354(01)00480-8.
RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) is a nitramine explosive that has contaminated soil and groundwater at military installations throughout the US. Although anaerobic RDX metabolism has been reported, the process is not well understood, as past studies have typically involved complex, undefined media with multiple potential electron donors and acceptors. In this study, bacteria enriched from RDX-contaminated aquifer sediments consumed RDX in a defined, bicarbonate-buffered, anaerobic medium containing hydrogen as the sole electron donor and RDX as a potential electron acceptor and sole nitrogen source. RDX was not consumed in live controls that did not contain hydrogen. Transient formation of mononitroso- and dinitroso-RDX metabolites (hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine and hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine, respectively) was documented by liquid chromatography-mass spectrometry. However, studies with 14C-labeled RDX suggested that mineralization to carbon dioxide was negligible (<2%), which is consistent with cometabolic transformation. Several lines of evidence suggest that the RDX-transforming bacteria under study were homoacetogens, including correlations between RDX consumption and acetate production. Methanogens were unlikely to be responsible for RDX metabolism, as the presence of 2-bromoethanesulfonate, an inhibitor of methanogenesis, did not appear to affect RDX metabolism. The presence of nitrate reversibly halted RDX metabolism, whereas ammonium had no discernible effect, which implies that: (i) nitrate, which commonly occurs in RDX-contaminated groundwater, may inhibit in situ RDX metabolism, and (ii) although RDX may act as both a nitrogen source and cometabolic electron sink, the latter role predominates, as RDX reduction will proceed regardless of whether or not a more favorable nitrogen source is present.
黑索今(六氢-1,3,5-三硝基-1,3,5-三嗪)是一种硝胺炸药,已在美国各地的军事设施中污染了土壤和地下水。尽管已有关于黑索今厌氧代谢的报道,但该过程尚未得到充分了解,因为过去的研究通常涉及含有多种潜在电子供体和受体的复杂、成分不明的培养基。在本研究中,从受黑索今污染的含水层沉积物中富集的细菌,在一种特定的、以碳酸氢盐缓冲的厌氧培养基中消耗黑索今,该培养基以氢气作为唯一电子供体,黑索今作为潜在电子受体和唯一氮源。在不含氢气的活对照组中,黑索今未被消耗。通过液相色谱-质谱法记录了单亚硝基和二亚硝基黑索今代谢物(分别为六氢-1-亚硝基-3,5-二硝基-1,3,5-三嗪和六氢-1,3-二亚硝基-5-硝基-1,3,5-三嗪)的瞬时形成。然而,用14C标记的黑索今进行的研究表明,矿化生成二氧化碳的量可忽略不计(<2%),这与共代谢转化一致。几条证据表明,所研究的黑索今转化细菌是同型产乙酸菌,包括黑索今消耗与乙酸盐产生之间的相关性。产甲烷菌不太可能负责黑索今的代谢,因为产甲烷抑制剂2-溴乙烷磺酸盐的存在似乎并未影响黑索今的代谢。硝酸盐的存在可逆地停止了黑索今的代谢,而铵盐没有明显影响,这意味着:(i)通常存在于受黑索今污染的地下水中的硝酸盐可能会抑制原位黑索今代谢,(ii)尽管黑索今可能同时作为氮源和共代谢电子阱,但后者的作用占主导,因为无论是否存在更有利的氮源,黑索今的还原都会进行。