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1.
Influence of environmental factors on 2,4-dichlorophenoxyacetic acid degradation by Pseudomonas cepacia isolated from peat 总被引:1,自引:0,他引:1
A Pseudomonas cepacia, designated strain BRI6001, was isolated from peat by enrichment culture using 2,4-dichlorophenoxyacetic acid (2,4-D) as the sole carbon source. BRI6001 grew at up to 13 mM 2,4-D, and degraded 1 mM 2,4-D at an average starting population density as low as 1.5 cells/ml. Degradation was optimal at acidic pH, but could also be inhibited at low pH, associated with chloride release from the substrate, and the limited buffering capacity of the growth medium. The only metabolite detected during growth on 2,4-D was 2,4-dichlorophenol (2,4-DCP), and degradation of the aromatic nucleus was by intradiol cleavage. Growth lag times prior to the on-set of degradation, and the total time required for degradation, were linearly related to the starting population density and the initial 2,4-D concentration. BRI6001, grown on 2,4-D, oxidized a variety of structurally similar chlorinated aromatic compounds accompanied by stoichiometric chloride release. 相似文献
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Biotransformation of 2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-Hexaazaisowurtzitane (CL-20) by Denitrifying Pseudomonas sp. Strain FA1 下载免费PDF全文
The microbial and enzymatic degradation of a new energetic compound, 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), is not well understood. Fundamental knowledge about the mechanism of microbial degradation of CL-20 is essential to allow the prediction of its fate in the environment. In the present study, a CL-20-degrading denitrifying strain capable of utilizing CL-20 as the sole nitrogen source, Pseudomonas sp. strain FA1, was isolated from a garden soil. Studies with intact cells showed that aerobic conditions were required for bacterial growth and that anaerobic conditions enhanced CL-20 biotransformation. An enzyme(s) involved in the initial biotransformation of CL-20 was shown to be membrane associated and NADH dependent, and its expression was up-regulated about 2.2-fold in CL-20-induced cells. The rates of CL-20 biotransformation by the resting cells and the membrane-enzyme preparation were 3.2 ± 0.1 nmol h−1 mg of cell biomass−1 and 11.5 ± 0.4 nmol h−1 mg of protein−1, respectively, under anaerobic conditions. In the membrane-enzyme-catalyzed reactions, 2.3 nitrite ions (NO2−), 1.5 molecules of nitrous oxide (N2O), and 1.7 molecules of formic acid (HCOOH) were produced per reacted CL-20 molecule. The membrane-enzyme preparation reduced nitrite to nitrous oxide under anaerobic conditions. A comparative study of native enzymes, deflavoenzymes, and a reconstituted enzyme(s) and their subsequent inhibition by diphenyliodonium revealed that biotransformation of CL-20 is catalyzed by a membrane-associated flavoenzyme. The latter catalyzed an oxygen-sensitive one-electron transfer reaction that caused initial N denitration of CL-20. 相似文献
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Abstract A class of very potent nucleoside transport inhibitors is present in two molecular forms around physiological pH. We investigated whether the monoprotonated or the unionized species of these molecules binds to this camer protein with higher affinity. 相似文献
5.
Christopher I Keeling Macaire MS Yuen Nancy Y Liao T Roderick Docking Simon K Chan Greg A Taylor Diana L Palmquist Shaun D Jackman Anh Nguyen Maria Li Hannah Henderson Jasmine K Janes Yongjun Zhao Pawan Pandoh Richard Moore Felix AH Sperling Dezene P W Huber Inanc Birol Steven JM Jones Joerg Bohlmann 《Genome biology》2013,14(3):R27
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A. Daneshjoo AH. Mokhtar N. Rahnama A. Yusof 《Biology of sport / Institute of Sport》2013,30(4):281-288
The study investigates the effects of the 11+ and HarmoKnee injury prevention programmes on knee strength in male soccer players. Under-21-year-old players (n=36) were divided equally into: the 11+, HarmoKnee and control groups. The programmes were performed for 24 sessions (20-25 min each). The hamstrings and quadriceps strength were measured bilaterally at 60°·s-1, 180°·s-1 and 300°·s-1. The concentric quadriceps peak torque (PT) of the 11+ increased by 27.7% at 300°·s-1 in the dominant leg (p<0.05). The concentric quadriceps PT of HarmoKnee increased by 36.6%, 36.2% and 28% in the dominant leg, and by 31.3%, 31.7% and 20.05% at 60°·s-1, 180°·s-1 and 300°·s-1 in the non-dominant leg respectively. In the 11+ group the concentric hamstring PT increased by 22%, 21.4% and 22.1% at 60°·s-1, 180°·s-1 and 300°·s-1, respectively in the dominant leg, and by 22.3%, and 15.7% at 60°·s-1 and 180°·s-1, in the non-dominant leg. In the HarmoKnee group the hamstrings in the dominant leg showed an increase in PT by 32.5%, 31.3% and 14.3% at 60°·s-1, 180°·s-1 and 300°·s-1, and in the non-dominant leg hamstrings PT increased by 21.1% and 19.3% at 60°·s-1 and 180°·s-1 respectively. The concentric hamstrings strength was significantly different between the 11+ and control groups in the dominant (p=0.01) and non-dominant legs (p=0.02). The HarmoKnee programme enhanced the concentric strength of quadriceps. The 11+ and HarmoKnee programmes are useful warm-up protocols for improving concentric hamstring strength in young professional male soccer players. The 11+ programme is more advantageous for its greater concentric hamstring strength improvement compared to the HarmoKnee programme. 相似文献
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A new bacterial strain, isolated from groundwater contaminated with explosives, was characterized as a pink-pigmented facultative methylotroph, affiliated to the genus Methylobacterium. The bacterial isolate designated as strain GW2 was found capable of producing the homopolymer poly-3-hydroxybutyrate (PHB) from various carbon sources such as methanol, ethanol, and succinate. Methanol acted as the best substrate for the production of PHB reaching 40 % w/w dry biomass. PHB accumulation was observed to be a growth-associated process, so that there was no need for two-step fermentation. Optimal growth occurred at 0.5 % (v/v) methanol concentration, and growth was strongly inhibited at concentration above 2 % (v/v). Methylobacterium sp. strain GW2 was also able to accumulate the copolyester poly-3-hydroxybutyrate-poly-3-hydroxyvalerate (PHB/HV) when valeric acid was supplied as an auxiliary carbon source to methanol. After 66 h, a copolymer content of 30 % (w/w) was achieved with a PHB to PHV ratio of 1:2. Biopolymers produced by strain GW2 had an average molecular weight ranging from 229,350 to 233,050 Da for homopolymer PHB and from 362,430 to 411,300 Da for the copolymer PHB/HV. 相似文献
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Biodegradation of the Hexahydro-1,3,5-Trinitro-1,3,5-Triazine Ring Cleavage Product 4-Nitro-2,4-Diazabutanal by Phanerochaete chrysosporium 下载免费PDF全文
Diane Fournier Annamaria Halasz Jim Spain Ronald J. Spanggord Jeffrey C. Bottaro Jalal Hawari 《Applied microbiology》2004,70(2):1123-1128
Initial denitration of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by Rhodococcus sp. strain DN22 produces CO2 and the dead-end product 4-nitro-2,4-diazabutanal (NDAB), OHCNHCH2NHNO2, in high yield. Here we describe experiments to determine the biodegradability of NDAB in liquid culture and soils containing Phanerochaete chrysosporium. A soil sample taken from an ammunition plant contained RDX (342 μmol kg−1), HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine; 3,057 μmol kg−1), MNX (hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine; 155 μmol kg−1), and traces of NDAB (3.8 μmol kg−1). The detection of the last in real soil provided the first experimental evidence for the occurrence of natural attenuation that involved ring cleavage of RDX. When we incubated the soil with strain DN22, both RDX and MNX (but not HMX) degraded and produced NDAB (388 ± 22 μmol kg−1) in 5 days. Subsequent incubation of the soil with the fungus led to the removal of NDAB, with the liberation of nitrous oxide (N2O). In cultures with the fungus alone NDAB degraded to give a stoichiometric amount of N2O. To determine C stoichiometry, we first generated [14C]NDAB in situ by incubating [14C]RDX with strain DN22, followed by incubation with the fungus. The production of 14CO2 increased from 30 (DN22 only) to 76% (fungus). Experiments with pure enzymes revealed that manganese-dependent peroxidase rather than lignin peroxidase was responsible for NDAB degradation. The detection of NDAB in contaminated soil and its effective mineralization by the fungus P. chrysosporium may constitute the basis for the development of bioremediation technologies. 相似文献
10.
CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane) (C(6)H(6)N(12)O(12)), a future-generation high-energy explosive, is biodegradable by Pseudomonas sp. strain FA1 and Agrobacterium sp. strain JS71; however, the nature of the enzyme(s) involved in the process was not understood. In the present study, salicylate 1-monooxygenase, a flavin adenine dinucleotide (FAD)-containing purified enzyme from Pseudomonas sp. strain ATCC 29352, biotransformed CL-20 at rates of 0.256 +/- 0.011 and 0.043 +/- 0.003 nmol min(-1) mg of protein(-1) under anaerobic and aerobic conditions, respectively. The disappearance of CL-20 was accompanied by the release of nitrite ions. Using liquid chromatography/mass spectrometry in the negative electrospray ionization mode, we detected a metabolite with a deprotonated mass ion [M - H](-) at 345 Da, corresponding to an empirical formula of C(6)H(6)N(10)O(8), produced as a result of two sequential N denitration steps on the CL- 20 molecule. We also detected two isomeric metabolites with [M - H](-) at 381 Da corresponding to an empirical formula of C(6)H(10)N(10)O(10). The latter was a hydrated product of the metabolite C(6)H(6)N(10)O(8) with addition of two H(2)O molecules, as confirmed by tests using (18)O-labeled water. The product stoichiometry showed that each reacted CL-20 molecule produced about 1.7 nitrite ions, 3.2 molecules of nitrous oxide, 1.5 molecules of formic acid, and 0.6 ammonium ion. Diphenyliodonium-mediated inhibition of salicylate 1-monooxygenase and a comparative study between native, deflavo, and reconstituted enzyme(s) showed that FAD site of the enzyme was involved in the biotransformation of CL-20 catalyzed by salicylate 1-monooxygenase. The data suggested that salicylate 1-monooxygenase catalyzed two oxygen-sensitive single-electron transfer steps necessary to release two nitrite ions from CL-20 and that this was followed by the secondary decomposition of this energetic chemical. 相似文献