Thermal deactivation of high-affinity H2 uptake activity in soils

Soils are the most important sink for atmospheric hydrogen, which is assumed to be oxidized by abiontic soil hydrogenases or by putative high-affinity hydrogenases of microbial origin. The activity of soil hydrogenases has been found to change with soil temperature as it changes during the day and the season. However, it is unclear whether and to which extent the soil hydrogenases are deactivated by increased temperature. Therefore, we incubated soils from different climates and different ecosystems (forest, agricultural, arid, hyper-arid, paddy, peat) at elevated temperature and measured the residual activity at 25 °C after different incubation times. We found that at least part of the soil hydrogenase is deactivated irreversibly already at relatively low temperatures (>30 °C) and short exposure times (>10 min) and that the deactivation was more pronounced in soil from cold versus hot climate. The deactivation kinetics could be fitted to a biexponential model, but were complex with respect to soil type and deactivation temperature. The results show that new hydrogenase activity has to be generated in the soil to compensate for activity loss by diurnal and seasonally increased temperature.     

产甲烷菌氢化酶活力分析条件的研究

本文叙述了厌氧消化系中微生物的甲基紫精(methyl viologen,其缩写为MV)氢化酶(Hase)活力分析条件的研究,包括酶反应进程曲线,底物饱和常数,反应最适pH,最适温度,反应底物最适加量,试样中乙酸对酶反应的影响等;侧重介绍了添加抗菌素penicillin—G处理消化污泥,抑制混合菌群中非产CH_4菌氢化酶活性以及选择性地测定产CH_4菌氢化酶活性的实验技术的研究。实验最终提出了检测污泥试样产CH_4菌的MV氢化酶活性的实验流程,并以此作为检测厌氧消化污泥产CH_4潜势的一种生化预测指标,实验得到了良好的效果。     

Hydrogen metabolism and nitrogen fixation of soybean (Glycine max. L.) inoculated with different strains ofRhizobium spp.

Summary Hydrogenase activities and N₂-fixing capacities of soybean nodules (Glycine max. cv. Hodgson), inoculated with strains ofBradyrhizobium japonicum andRhizobium fredii from different geographical regions, were measured after 35 days of culture under controlled conditions. Of the strains tested, 47% induced nodules with bacteroids which recycled H₂. The data obtained suggest that H₂-recycling ability is not a major factor influencing early N₂-fixation which depends essentially on the precocity and intensity of the initial nodulation.     

厌氧发酵法生物制氢研究进展

以农作物秸秆等廉价资源为原料,与废弃生物质处理相结合,采用厌氧发酵法制取氢气的技术具有很大的潜力和发展空间.为此,论述了发酵法生物制氢领域的研究进展,分别对产氢相关的酶、发酵类型、氢酶基因的研究以及废弃生物质制氢技术进行了介绍,分析了发酵制氢的可行性,并对目前存在的问题进行了总结和展望.     

Acetylene reduction,hydrogen evolution and nodule respiration in Phaseolus vulgaris

Summary In an experiment performed under greenhouse conditions, four cultivars of Phaseolus vulgaris L. (Venezuela-350; Aroana; Moruna; Carioca) were inoculated with three Rhizobium leguminosarum biovar phaseoli strains (C-05; C-40 = CIAT 255; C-89 = CIAT 55) and were fertilized with an N-free mineral nutrient solution. The plants were harvested 25, 40, and 55 days after emergence and the following paramenters were evaluated: Nitrogenase activity of nodulated roots, H₂ evolution by the nodules; relative efficiency of nitrogenase; respiration rates of nodulated roots and detached nodules; dry weight and total N of stems, leaves, pods, roots, and nodules. Generally the bean cultivar, Rhizobium strain, had an effect and there was an interaction effect with both symbiotic partners, on all parameters. On average, nodules represented 23% of total root respiration but the best symbiotic combinations showed lower ratios of C respired to N fixed. The maximum N-assimilation rate (between 40 and 55 days after emergence) of 11.93 mg N plant^–1 day^–1 occurred with the symbiotic combination of Carioca × C-05, while the poorest rate of 0.55 mg N plant^–1 day^–1 was recorded with Venezuela-350 × C-89. The best symbiotic combinations always showed the highest relative nitrogenase efficiency, but the differences in N₂-fixation rates cannot be explained solely in terms of conservation of energy by recycling of H₂. This requires further investigation.     

梭菌氢酶基因部分片段的同源克隆及敲除载体的构建

为从分子水平探索典型铁还原菌-梭菌的铁还原能力与其氢酶产氢之间的关系,以从水稻土中分离得到一株具有高铁还原能力和高产氢能力的梭菌为材料,通过同源克隆获得长度为761bp氢酶基因的部分序列。生物信息分析发现,该基因片段覆盖氢酶的活性中心,是氢酶的主要功能结构域。采用Overlap PCR的方法构建含有四环素抗性基因的氢酶基因敲除载体(pMD-19-HTH),以期进一步构建氢酶基因缺失的梭菌突变体,为分析氢酶产氢与铁还原的关系奠定基础。     

氢气代谢及其环境生物修复功能研究进展

分子氢是多种微生物代谢之间相互作用的关键中介物,环境中产氢微生物和耗氢微生物的活动决定了全球氢气循环,对其他重要元素生物地球化学循环具有潜在的驱动作用。环境功能微生物在维持环境生态系统平衡、消除次生环境污染等领域中扮演着不容忽视的重要作用。因此,理解环境中氢气代谢（氢气的产生和消耗）微生物对生态环境的影响及其在环境生物修复中的作用与功能,对认识氢气的生态环境效应并将该生物能源应用于生物修复具有重要的科学意义和实践价值。系统分析了氢气代谢过程及氢化酶的分类和功能,总结了微生物产生和消耗氢气的多种途径及其对土壤生态环境效应和生物修复作用的影响,指出了目前氢气代谢过程及氢化酶应用于环境生物修复领域存在的关键科学技术问题,提出了未来的研究思路与重点方向,以推动氢气这种生物能源成就一种有前景的环境污染修复策略。