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1.
Biodegradation of explosives in groundwater represents a promising remedial approach for these compounds. Although a range of bacteria capable of degrading the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in pure culture have been described, the role of these known strains (and the genera they represent) during RDX degradation in groundwater has not been established. RDX-contaminated groundwater was collected from the Pueblo Chemical Depot (CO, USA) and the Picatinny Arsenal (NJ, USA) where bioremediation technologies are being tested. Soil columns and enrichment cultures were derived from Picatinny Arsenal groundwater. Bacteria-specific primers were used to amplify the 16S rRNA genes that were used for phylogenetic analysis. The species detected ranged across multiple genera, many of which have not been previously associated with RDX biodegradation. None of the retrieved sequences were exact matches to previously described RDX-degrading strains, although multiple sequences that grouped with known explosive-degrading strains of Clostridium and Pseudomonas were recovered. Genes previously reported to be associated with RDX degradation, including xplA, hydA, onr, xenA, and xenB, were not detected in any of the groundwater samples. These preliminary results indicate that the previously described RDX-degrading bacteria likely do not capture the microbial diversity associated with RDX bioremediation in groundwater, especially under the general biostimulation approaches used during most remediation efforts.  相似文献   

2.
    
The consideration of multiple or cumulative sources of exposure to a chemical is important for adequately protecting human health. This assessment demonstrates one way to consider multiple or cumulative sources through the development of a relative source contribution (RSC) factor for the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), using the Exposure Decision Tree approach (subtraction method) recommended by the U.S. Environmental Protection Agency. The RSC factor is used to ensure that the concentration of a chemical allowed by a regulatory criterion or multiple criteria, when combined with other identified sources of exposure common to the population of concern, will not result in unacceptable exposures. An exposure model was used to identify relevant potential sources for receptors. Potential exposure pathways include ingestion of soil, water, contaminated local crops and fish, and dermal contact with soil and water. These pathways are applicable only to areas that are in close proximity to current or former military bases where RDX may have been released into the environment. Given the physical/chemical properties and the available environmental occurrence data on RDX, there are adequate data to support a chemical-specific RSC factor for RDX of 50% for drinking water ingestion.  相似文献   

3.
    
Alkaline hydrolysis and subcritical water degradation were investigated as ex-situ remediation processes to treat explosive-contaminated soils from military training sites in South Korea. The addition of NaOH solution to the contaminated soils resulted in rapid degradation of the explosives. The degradation of explosives via alkaline hydrolysis was greatly enhanced at pH ≥12. Estimated pseudo-first-order rate constants for the alkaline hydrolysis of 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in contaminated soil at pH 13 were (9.6?±?0.1)×10?2, (2.2?±?0.1)×10?1, and (1.7?±?0.2)×10?2 min?1, respectively. In the case of subcritical water degradation, the three explosives were completely removed at 200–300°C due to oxidation at high temperatures and pressures. The degradation rate increased as temperature increased. The pseudo-first-order rate constants for DNT, TNT, and RDX at 300°C were (9.4?±?0.8)×10?2, (22.8?±?0.3)×10?2, and (16.4?±?1.0)×10?2, respectively. When the soil-to-water ratio was more than 1:5, the extent of alkaline hydrolysis and subcritical water degradation was significantly inhibited.  相似文献   

4.
Undersea deposition of unexploded ordnance (UXO) constitutes a potential source of contamination of marine environments by hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). Using sediment from a coastal UXO field, Oahu Island, Hawaii, we isolated four novel aerobic RDX-degrading fungi HAW-OCF1, HAW-OCF2, HAW-OCF3 and HAW-OCF5, tentatively identified as members of Rhodotorula, Bullera, Acremonium and Penicillium, respectively. The four isolates mineralized 15–34% of RDX in 58 days as determined by liberated 14CO2. Subsequently we selected Acremonium to determine biotransformation pathway(s) of RDX in more details. When RDX (100 μM) was incubated with resting cells of Acremonium we detected methylenedinitramine (MEDINA), N2O and HCHO. Also we detected hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX) together with trace amounts of hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX) and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX). Under the same conditions MNX produced N2O and HCHO together with trace amounts of DNX and TNX, but we were unable to detect MEDINA. TNX did not degrade with Acremonium. These experimental findings suggested that RDX degraded via at least two major initial routes; one route involved direct ring cleavage to MEDINA and another involved reduction to MNX prior to ring cleavage. Nitrite was only detected in trace amounts suggesting that degradation via initial denitration did take place but not significantly. Aerobic incubation of Acremonium in sediment contaminated with RDX led to enhanced removal of the nitramine.  相似文献   

5.
    
Contamination of soils with the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX, Research Department Explosive) as a result of military applications is a large-area problem globally. Since coniferous trees dominate the vegetation of large areas of military land in Central Europe, particularly in Germany, the long-term fate of 14C-RDX in the conifers Scots pine and Dwarf Alberta spruce was studied. Acetic acid was the most effective solvent for the removal of extractable RDX residues from homogenates of RDX-laden tree material (85%, 80–90% and 64–80% for roots, wood and needles, respectively). On average, only a fifth of RDX-derived 14C was bound in non-extractable residues (NER). Within the main cell wall compartments, lignin was the dominant binding site for NER (needles: 32–62%; roots: 38–42%). Hemicellulose (needles: 11–18%; roots: 6–11%) and cellulose (needles: 12–24%; roots: 1–2%) were less involved in binding and a considerable proportion of NER (needles: 15–24%; roots: 59–51%) was indigestible. After three-year incubation in rot chambers, mineralisation of tree-associated 14C-RDX to 14CO2 clearly dominated the mass balance in both tree species with 48–83%. 13–33% of 14C-RDX-derived radioactivity remained in an unleachable form and the remobilisation by water leaching was negligible (< 2%).  相似文献   

6.
7.
Past handling practices associated with the manufacturing and processing of the high explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has resulted in extensive environmental contamination. In-situ biodegradation is a promising technology for remediating RDX contaminated sites but often relies on the addition of a cosubstrate. A sulfate-reducing bacterium isolated from an RDX-degrading enrichment culture was studied for its ability to grow on RDX as a sole source of carbon and nitrogen and for its ability to mineralize RDX in the absence of a cosubstrate. The results showed the isolate degraded 140 μM RDX in 63 days when grown on RDX as a carbon source. Biomass within the carbon limited culture increased 9-fold compared to the RDX unamended controls. When the isolate was incubated with RDX as sole source of nitrogen it degraded 160 μM RDX in 41 days and exhibited a 4-fold increase in biomass compared to RDX unamended controls. Radiolabeled studies under carbon limiting conditions with 14C-hexahydro-1,3,5-trinitro-1,3,5-triazine confirmed mineralization of the cyclic nitramine. After 60 days incubation 26% of the radiolabel was recovered as 14CO2, while in the control bottles less than 1% of the radiolabel was recovered as 14CO2. Additionally, ~2% of the radiolabeled carbon was found to be associated with the biomass. The 16S rDNA gene was sequenced and identified the isolate as a novel species of Desulfovibrio, having a 95.1% sequence similarity to Desulfovibrio desulfuricans. This is the first known anaerobic bacterium capable of mineralizing RDX when using it as a carbon and energy source for growth.  相似文献   

8.
    
Referee: Dr. C. Neal Stewart, Jr., Department of Plant Science and Landscape Systems, The University of Tennessee, 2431 Center Drive, Knoxville, TN 37996-4561 There is major international concern over the widescale contamination of soil and associated groundwater by persistant explosives residues. The development of methods to remediate these contaminants has been a significant research interest for several decades. In the last 10 years, phytoremediation has emerged as a focus for explosives remediation because of its low cost, low energy requirements, and promising research observing explosives removal from contaminated groundwater and soil. More recent work has focused on the modes of transformation and metabolism of energetic compounds by plants. These biochemical studies and the experimental conditions enabling the degradation and uptake of explosives by different plant species are discussed.  相似文献   

9.
Manna A  Paul AK 《Biodegradation》2000,11(5):323-329
Poly(3-hydroxybutyrate) [P(3HB)] test-pieces prepared from the polymer produced by Azotobacter chroococcum were degraded in natural environments like soil, water, compost and sewage sludge incubated under laboratory conditions. Degradation in terms of % weight loss of the polymer was maximum (45%) in sewage sludge after 200 days of incubation at 30°C. The P(3HB)-degrading bacterial cultures (36) isolated from degraded test-pieces showed different degrees of degradation in polymer overlayer method. The extent of P(3HB) degradation increases up to 12 days of incubation and was maximum at 30°C for majority of the cultures. For most efficient cultures the optimum concentration of P(3HB) for degradation was 0.3% (w/v). Supplementation of soluble carbon sources like glucose, fructose and arabinose reduced the degradation while it was almost unaffected with lactose. Though the cultures degraded P(3HB) significantly, they were comparatively less efficient in utilizing copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate [P(3HB-co-3HV)].  相似文献   

10.
A new thermophilic microorganism capable of degrading poly(D-3-hydroxybutyrate) (PHB) was isolated from soil. A phylogenetic analysis based on 16S rDNA sequences indicated that the new isolate belongs to genus Streptomyces. PHB film and powder were completely degraded after 6 and 3 d cultivation, respectively at 50 degrees C. Scanning micrographs showed adherence of the microbial cells to the entire film surface, indicating that biodegradation occurs by colonization of the PHB surface. The film was degraded both by microbial attack and by the action of an extracellular enzyme secreted by the microorganism. The strain can also degrade poly(ethylene succinate), poly(ester carbonate), polycaprolactone and poly(butylene succinate), but to a lesser extent.  相似文献   

11.
    
Inorganic pyrophosphatases are potential targets for the development of novel antibacterial agents. A pyrophosphatase-coupled high-throughput screening assay intended to detect o-succinyl benzoic acid coenzyme A (OSB CoA) synthetase inhibitors led to the unexpected discovery of a new series of novel inorganic pyrophosphatase inhibitors. Lead optimization studies resulted in a series of 3-(3-aryl-pyrrolidin-1-yl)-5-aryl-1,2,4-triazine derivatives that were prepared by an efficient synthetic pathway. One of the tetracyclic triazine analogues 22h displayed promising antibiotic activity against a wide variety of drug-resistant Staphylococcus aureus strains, as well as activity versus Mycobacterium tuberculosis and Bacillus anthracis, at a concentration that was not cytotoxic to mammalian cells.  相似文献   

12.
多环芳烃微生物降解基因的研究进展   总被引:10,自引:2,他引:10  
郑乐  刘宛  李培军 《生态学杂志》2007,26(3):449-454
多环芳烃(PAHs)是环境中普遍存在的一类有机污染物,微生物的降解是PAHs去除的主要途径。近年来,有关PAHs微生物降解途径和代谢产物的研究已有很多报道。小分子PAHs一般可以直接被微生物降解,而大分子PAHs则需要微生物以共代谢的方式降解。在过去20年中,微生物降解PAHs的基因相继被发现,各种基因在调控PAHs降解过程中的功能也越来越清晰。本文概述了PAHs微生物降解基因方面的研究进展,详细介绍了微生物对萘、菲的降解基因,最后对PAHs微生物降解基因的应用前景进行了展望。  相似文献   

13.
甲胺磷降解菌的筛选及降解特性研究   总被引:7,自引:0,他引:7  
从长期受有机磷农药污染的土壤中分离到1株能降解甲胺磷的菌株B15,经生理生化鉴定为巨大芽孢杆菌(Bacillus megaterium)。在甲胺磷无机盐培养基(甲胺磷浓度为0.5%)生长时,最适生长温度为28℃,最适pH为7.0,摇床培养(28℃190 r/min)48 h降解率达到83%。菌株在甲胺磷浓度为1%的无机盐培养基上能生长,但是在甲胺磷浓度为0.5%的无机盐培养基上生长最好,降解率最高。外加碳氮源对菌株的降解率有所提高,但是超过某一浓度降解率随着浓度的增加反而下降。  相似文献   

14.
细菌降解萘、菲的代谢途径及相关基因的研究进展   总被引:2,自引:0,他引:2       下载免费PDF全文
多环芳烃(Polycyclic aromatic hydrocarbons,PAHs)是一类在环境中广泛存在的具有毒性的污染物,微生物降解是其在自然界中降解的主要途径,因而尤为重要。随着研究的深入,关于微生物降解PAHs的分子降解机制、途径等的认识逐渐积累。以下对细菌降解萘、菲的研究进展进行了概述,介绍了萘的水杨酸降解途径,菲的水杨酸、邻苯二甲酸及其他降解途径,同时也包括降解过程中涉及的降解基因簇,如nah-like、phn、phd、nid和nag等以及细菌在PAHs胁迫条件下其他相关基因的表达与调节等方面的最新进展。这些进展可为降解菌株的分子及遗传机制研究提供理论依据,将促进通过基因工程优化降解菌、更有效地检测PAHs环境污染及实现PAHs污染的生物修复。  相似文献   

15.
塑料广泛存在于人类的日常生活中,在给人们生活带来便利的同时,大量塑料废物也给环境带来很大压力。聚对苯二甲酸乙二醇酯(polyethylene terephthalate, PET)是一种以石油为原料的高分子热塑性材料,因其具有耐用、透明度高、重量轻等特性,已成为世界上使用最广泛的塑料之一。由于PET具有结构复杂以及难降解的特性,可在自然界中长期存在,不仅对全球生态环境造成严重的污染,而且已经威胁到人类健康。如何对PET废弃物进行降解已成为全球的难题之一,相较于物理法和化学法,生物降解法是目前处理PET废弃物最为绿色环保的方法。本文分别介绍了微生物和生物酶对PET生物降解的研究现状、PET的生物降解途径、PET生物降解机制以及PET降解酶的分子改造等方面的研究,并对如何实现PET的高效降解、寻找和改造可降解高结晶度PET的微生物或酶进行展望,为PET的生物降解微生物或酶的有效开发应用提供理论依据。  相似文献   

16.
Type 5 17β-hydroxysteroid dehydrogenase (17β-HSD5), also known as aldo-keto reductase 1C3 (AKR1C3), is a member of the aldo-keto reductase superfamily of enzymes and is expressed in the human prostate. One of the main functions of 17β-HSD5 is to catalyze the conversion of the weak androgen, androstenedione, to the potent androgen, testosterone. The concentration of intraprostatic 5α-dihydrotestosterone (DHT) in patients following chemical or surgical castration has been reported to remain as high as 39% of that of healthy men, with 17β-HSD5 shown to be involved in this androgen synthesis. Inhibition of 17β-HSD5 therefore represents a promising target for the treatment of castration-resistant prostate cancer (CRPC). To investigate this, we conducted high-throughput screening (HTS) and identified compound 2, which displayed a structure distinct from known 17β-HSD5 inhibitors. To optimize the inhibitory activity of compound 2, we first introduced a primary alcohol group. We then converted the primary alcohol group to a tertiary alcohol, which further enhanced the inhibitory activity, improved metabolic stability, and led to the identification of compound 17. Oral administration of compound 17 to castrated nude mice bearing the CWR22R xenograft resulted in the suppression of androstenedione (AD)-induced intratumoral testosterone production. Compound 17 also demonstrated good isoform selectivity, minimal inhibitory activity against either CYP or hERG, and enhanced pharmacokinetic and physicochemical properties.  相似文献   

17.
    
Zika virus (ZIKV), a positive-sense single-stranded RNA virus, causes congenital ZIKV syndrome in children and Guillain-Barré Syndrome (GBS) in adults. ZIKV expresses nonstructural protein 5 (NS5), a large protein that is essential for viral replication. ZIKV NS5 confers the ability to evade interferon (IFN) signalling; however, the exact mechanism remains unclear. In this study, we employed affinity pull-down and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses and found that splicing factor 3b subunit 3 (SF3B3) is associated with the NS5-Flag pull-down complex through interaction with NS5. Functional assays showed that SF3B3 overexpression inhibited ZIKV replication by promoting IFN-stimulated gene (ISG) expression whereas silencing of SF3B3 inhibited expression of ISGs to promote ZIKV replication. GTP cyclohydrolase I (GCH1) is the first and rate-limiting enzyme in tetrahydrobiopterin (BH4) biosynthesis. NS5 upregulates the expression of GCH1 during ZIKV infection. And GCH1 marginally promoted ZIKV replication via the IFN pathway. Additionally, GCH1 expression is related to the regulation of SF3B3. Overexpression of the SF3B3 protein effectively reduced GCH1 protein levels, whereas SF3B3 knockdown increased its levels. These findings indicated that ZIKV NS5 binding protein SF3B3 contributed to the host immune response against ZIKV replication by modulating the expression of GCH1.  相似文献   

18.
聚3-羟基丁酸酯(PHB)生物降解过程的研究   总被引:8,自引:0,他引:8       下载免费PDF全文
利用DS9701菌株对聚3-羟基丁酸酯(PHB)膜进行降解,对降解到不同程度的PHB膜采用扫描电子显微镜观察其表面形态结构的变化,并对其降解产物进行分析测定.结果表明,PHB的生物降解首先发生在PHB表面的非晶部分,随后结晶部分开始降解,并且降解首先发生在球晶的中心部分.DS9701菌株所产生的PHB解聚酶主要降解PHB的第二个酯键,降解产物为二聚体.  相似文献   

19.
20.
十溴联苯醚降解菌群的降解特性与组成分析   总被引:2,自引:0,他引:2       下载免费PDF全文
[目的]针对水体沉积物中日益严重的多溴联苯醚污染问题,以电子垃圾污染河床沉积物为种源富集驯化获得的菌群Cf3,研究该菌群对十溴联苯醚的降解特性以及其菌群结构组成.[方法]通过GC-MS分析十溴联苯醚降解后低溴代产物组成,并测定其降解率;通过DGGE技术分析了该BDE-209降解菌群的结构组成.[结果]菌群Cf3具有较强降解BDE-209的能力,经过120 d的培养,初始量为2.6 μmol的BDE-209降解率达到80.03%,OD600从0.01增长到0.21,pH由初始的6.93增加到反应结束时的8.50.菌群Cf3经过单菌落分离,共获得10株可培养细菌,通过16S rRNA基因序列比对发现,其中6株与柠檬酸杆菌属(Citrobacter spp.)具有较高同源性,其余4株与产碱杆菌属(Alcaligenes spp.)较相似.进一步采用DGGE分析菌群Cf3的结构组成时发现,除了分离得到的2个菌属外,该菌群中还含有拟杆菌属(Wolinella spp.)、氨基酸球菌属(Acidaminococcus spp.),以及随着降解时间延长而消失的脱硫弧菌属(Desulfovibrio spp.)和醋杆菌属(Acetobacterium spp.).[结论]获得了具有较强多溴联苯醚降解能力的菌群,并分析了其降解特性和群落组成,为进一步开展溴代阻燃剂等持久性有机污染物的生物修复提供宝贵的菌种资源和科学数据.  相似文献   

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