鱼类解偶联蛋白（UCP）基因研究新进展

通过生理性解偶联调节氧化磷酸化效率可能是进化早期发展起来的一种普遍策略，对生命的存在至关重要. 解偶联蛋白（uncoupling protein，UCP）家族是位于线粒体内膜的转运蛋白，哺乳动物基因组中已发现5个成员，其中UCP1~UCP3紧密相关，而UCP4和UCP5（即BMCP1，brain mitochondrial carrier protein-1）与它们差异较大. UCP1~UCP4不仅在哺乳类、鸟类等恒温脊椎动物中普遍存在，而且在鱼类等变温动物中也被证实存在，但UCP5目前仅在哺乳类中被发现. 哺乳动物褐色脂肪组织的UCP1，介导呼吸链产生的质子梯度泄漏，使氧化产生的能量以热的形式散发，但鱼类等变温动物UCP1的功能尚待进一步研究确立. UCP2和UCP3在产热、控制活性氧生成、脂肪酸氧化以及肥胖、糖尿病的发生中均发挥重要作用，二者的转录调节较复杂. UCP4和UCP5与其他UCP关系较远，UCP4仅在脑中表达，而UCP5在脑中高表达，它们的功能还不十分明确，但研究表明很可能与UCP2和UCP3的功能相似.     

改良型氧化沟工艺调试与运行

介绍了娄底市第一污水处理厂一期工程设计概况和采用的改良型氧化沟脱氮除磷工艺,分析了该污水处理厂调试、培菌过程中出现的问题,并针对性地采取了一系列改进措施.在进水远低于设计值的不利条件下,通过合理培菌,不到一个月系统启动成功.监测结果表明:该工艺运行可靠,出水水质稳定、达标.     

氮肥、土壤湿度和温度对稻田土壤甲烷氧化的影响

Effects of nitrogen fertilizer,soil mosture and temperature and temperature on methane oxidation in paddy soil were investigated under laboratory conditions.Addition of 0.05 g N kg^-1 soil as NH4Cl strongly inhibited methane oxidation and addition of the same rate of KCl also inhibited the oxidation but with more slight effect,suggesting that the inhibitory effect was partly caused by increase in osmotic potential in microorganism cell,Not only NH4^ but also NO3^- greatly affected methane oxidation.Urea did not affect methane oxidation in paddy soil in the first two days of incubation,but strong inhibitory effect was observed afterwards.Methane was oxidized in the treated soil with an optimum moisture of 280 g kg^-1 ,and air-drying inhibited methane oxidation entirely.The optimum temperature of methane oxidation was about 30℃ in paddy soil.while no methane oxidation was observed at 5℃or 50℃。     

Labile carbon and methane uptake as affected by tillage intensity in a Mollisol

Methane (CH₄) oxidation potential of soils decreases with cultivation, but limited information is available regarding the restoration of that capacity with implementation of reduced tillage practices. A study was conducted to assess the impact of tillage intensity on CH₄ oxidation and several C-cycling indices including total and active microbial biomass C (t-MBC, a-MBC), mineralizable C (C_min) and N (N_min), and aggregate-protected C. Intact cores and disturbed soil samples (0–5 and 5–15 cm) were collected from a corn (Zea mays L.)–soybean (Glycine max L. Merr.) rotation under moldboard-plow (MP), chisel-plow (CP) and no-till (NT) for 8 years. An adjacent pasture (<25 years) and secondary growth forest (>60 years) soils were also sampled as references. At all sites, soil was a Kokomo silty clay loam (mesic Typic Argiaquolls). Significant tillage effects on t-MBC and protected C were found in the 0–5 cm depth. Protected C, a measure of C retained within macro-aggregates and defined as the difference in C_min (CO₂ evolved in a 56 days incubation) between intact and sieved (<2 mm) soil samples, amounted to 516, 162 and 121 mg C kg⁻¹ soil in the 0–5 cm layer of the forest, pasture and NT soils, respectively. Protected C was negligible in the CP and MP soils. Methane uptake rate (μg CH₄-C kg⁻¹ soil per day, under ambient CH₄) was higher in forest (2.70) than in pasture (1.22) and cropland (0.61) soils. No significant tillage effect on CH₄ oxidation rate was detected (MP: 0.82; CP: 0.41; NT: 0.61). These results underscore the slow recovery of the CH₄ uptake capacity of soils and suggest that, to have an impact, tillage reduction may need to be implemented for several decades.     

Effect of potassium phosphate fertilization on production and emission of methane and its C-stable isotope composition in rice microcosms

Rice fields are an important source for atmospheric CH₄, but the effects of fertilization are not well known. We studied the turnover of CH₄ in rice soil microcosms without and with addition of potassium phosphate. Height and tiller number of rice plants were higher in the fertilized than in the unfertilized microcosms. Emission rates of CH₄ were also higher, but porewater concentrations of CH₄ were lower. The δ¹³C values of the emitted CH₄ and of the CH₄ in the porewater were both 2-6% higher in the fertilized microcosms than in the control. Potassium phosphate did not affect rate and isotopic signature of CH₄ production in anoxic soil slurries. On the other hand, roots retrieved from fertilized microcosms at the end of incubation exhibited slightly higher CH₄ production rates and slightly higher CH₄-δ¹³C values compared to roots from unfertilized plants. Addition of potassium phosphate to excised rice roots generally inhibited CH₄ production and resulted in increasingly lower δ¹³C values of the produced CH₄. Fractionation of ¹³C during plant ventilation (i.e. δ¹³C in pore water CH₄ versus CH₄ emitted) was larger in the fertilized microcosms than in the control. Besides plant ventilation, this difference may also have been caused by CH₄ oxidation in the rhizosphere. However, calculation from the isotopic data showed that less than 27% of the produced CH₄ was oxidized. Collectively, our results indicate that potassium phosphate fertilization stimulated CH₄ emission by enhancing root methanogenesis, plant ventilation and/or CH₄ oxidation, resulting in residence times of CH₄ in the porewater in the order of hours.     

Soil organic matter in urban soils: Estimation of elemental carbon by thermal oxidation and characterization of organic matter by solid-state C nuclear magnetic resonance (NMR) spectroscopy

To reduce soil destruction by urban sprawl, land use planning has to promote the use of soils within cities. As soil functions are now protected by law in Germany, urban soil quality has to be evaluated before soil management. We studied contributions from elemental carbon (EC) and soil organic matter (SOM) quality in topsoil horizons at seven sites in Stuttgart, Germany, differing in impurities by technogenic substrates. The most disturbed site was found at a disused railway area while high-density areas, public parks and garden areas showed varying degrees of disturbance by anthropogenic activities. For most soils, compounds derived from plant litter dominated organic matter (OM) quality characterized by nuclear magnetic resonance (NMR) spectroscopy. Although high contents of EC (up to 70% of soil organic carbon) were indicated by thermal oxidation, this was not confirmed by aromatic C intensities in NMR spectra. Only for the highly aromatic railway soil were results for elemental carbon by thermal oxidation and NMR similar. As other technogenic substrates beside EC like plastics may also contribute in the long-term to OM in urban soils, new analytical techniques are therefore required. This knowledge will promote the evaluation of urban soil properties and their sustainable use.     

Manganese availability and microbial populations in the rhizosphere of wheat genotypes differing in tolerance to Mn deficiency

Plant genotypes differ in their capacity to grow in soils with low manganese (Mn) availability. The physiological mechanisms underlying differential tolerance to Mn deficiency are poorly understood. To study the relationship between Mn content in soil, plant genotypes, and rhizosphere microorganisms in differential Mn efficiency, two wheat (Triticum aestivum L.) cultivars, RAC891 (tolerant to Mn deficiency) and Yanac (sensitive), were grown in a Mn‐deficient soil to which 5, 10, 20 or 40 mg Mn kg^–1 were added. The shoot dry matter of both cultivars increased with increasing Mn addition to the soil. At all soil Mn fertilizer levels, the tolerant RAC891 had a greater shoot dry matter and a higher total shoot Mn uptake than the sensitive Yanac. The concentration of DTPA‐extractable Mn in the rhizosphere soil of RAC891 at Mn20 and Mn40 was slightly lower than in the rhizosphere of Yanac. The population density of culturable microorganisms in the rhizosphere soil was low (log 6.8–6.9 cfu (g soil)^–1) in both cultivars and neither Mn oxidation nor reduction were observed in vitro. To assess the non‐culturable fraction of the soil microbial community, the ribosomal intergenetic spacer region of the bacterial DNA in the rhizosphere soil was amplified (RISA) and separated in agarose gels. The RISA banding patterns of the bacterial rhizosphere communities changed markedly with increasing soil Mn level, but there were no differences between the wheat cultivars. The bacterial community structure in the rhizosphere was significantly correlated with the concentration of DPTA‐extractable Mn in the rhizosphere, fertilizer Mn level, shoot dry matter, and total shoot Mn uptake. The results obtained by RISA indicate that differential tolerance to Mn deficiency in wheat may not be related to changes in the composition of the bacterial community in the rhizosphere.     

Oxidation of methane in the rhizosphere of rice plants

Oxidation of CH₄ in the rhizosphere of rice plants was quantified using (1) methyl fluoride, a specific inhibitor of CH₄ oxidation, and (2) measuring changes in plant-mediated CH₄ emission after incubation under air, N₂, or 40% O₂. No significant rhizospheric CH₄ oxidation was observed from rice plants in the ripening stage. CH₄ emission from rice plants 1 week before panicle initiation increased by 40% if CH₄ oxidation in the rhizosphere was blocked. The growth stage of the rice plant is an important factor determining the rhizospheric CH₄ oxidation. Fluctuation of rhizospheric CH₄ oxidation during the growing season may help to explain the observed seasonal CH₄ emission patterns in field studies. Measurements from four rice varieties showed that one variety, Pokkali, had higher rhizospheric CH₄ oxidation. This was probably because Pokkali was in an earlier growth stage than the other three varieties. Both in the early and in the late growth stages, incubation under N₂ caused a much stronger CH₄ flux than inhibition of CH₄ oxidation alone. Apparently, N₂ incubation not only blocked CH₄ oxidation but also stimulated methanogenesis in the rhizosphere. Incubation under a higher O₂ atmosphere (40% O₂) than ambient air decreased the CH₄ flux, suggesting that increasing the oxidation of the rice rhizosphere may help in reducing CH₄ fluxes from rice agriculture. The O₂ pressure in the rhizosphere is an important factor that reduces the plant-mediated CH₄ flux. However, inhibition of methanogenesis in the rhizosphere may contribute more to CH₄ flux reduction than rhizospheric CH₄ oxidation.     

Impact of long-term N fertilization on the structural composition of spruce litter and mor humus

The aims of this study were to determine the degree of lignin degradation and to investigate changes in the chemical composition of the organic matter in the forest floor in an N fertilized Norway spruce forest soil. Needle litter and mor humus were collected from the field experiment at Skogaby in southern Sweden (56°33′N; 13°13′E). The spruce stand had been fertilized for 11 years with 100 kg N ha⁻¹ yr⁻¹ as (NH₄)₂SO₄. The degree of lignin degradation was determined with alkaline CuO oxidation followed by HPLC analysis. The chemical composition of the organic matter was characterized by CPMAS ¹³C NMR. Tannin was specifically analyzed using dipolar dephasing CPMAS ¹³C NMR and the N distribution was studied by CPMAS ¹⁵N NMR.The C-to-N ratios in the fertilized Oi and Oe layers were significantly lower than in the unfertilized layers (24 compared to 34 and 23 compared to 27, respectively). Neither the sum of the CuO oxidation products (Vanillyls+Syringyls+Cinnamyls expressed as VSC) nor the acid-to-aldehyde ratio ((Ac/Al)_V) showed any significant treatment effects. The content of aromatic C (including phenolic C) was significantly lower in the unfertilized than in the fertilized Oi layer (18 versus 21%). In the unfertilized soil, VSC was positively correlated (r=+0.63, p<0.05) with the C-to-N ratio, whereas the phenolic C content was negatively correlated (r=−0.61, p<0.05). The tannin index showed a tendency of increasing from Oi to Oe layers in both treatments. Most of the organic N was found as amide-N, whereas no heterocyclic N was detected. We have not been able to show any major C structural changes due to N fertilization. We suggest that the significantly higher content of aromatic and phenolic C in the fertilized Oi layer is due to an initial stimulation of the microbial community.