革兰氏阴性细菌外膜主要成分的跨膜转运机制研究进展

革兰氏阴性细菌的外膜由脂多糖、磷脂、外膜蛋白和脂蛋白等成分组成,是细菌抵御外界有害物质的首要物理屏障,与细菌致病性和耐药性密切相关.外膜各组分依赖特定的系统进行跨膜转运,包括脂多糖转运系统(lipopolysaccharide transport, Lpt)、脂质不对称维持系统(maintenance of lipid asymmetry, Mla)、β-桶状装配机器(β-barrel assembly machinery,Bam)以及脂蛋白定位系统(localization of lipoprotein,Lol).这些系统能够保证细菌外膜的完整与稳定,被视为维持细菌生命活动的"命门".因此,本文系统地综述革兰氏阴性细菌外膜主要成分的跨膜转运系统结构与功能,并对其未来研究方向进行展望,为新型靶向抗菌类药物研发提供新的思路.     

Local and global pyrogeographic evidence that indigenous fire management creates pyrodiversity

Despite the challenges wildland fire poses to contemporary resource management, many fire‐prone ecosystems have adapted over centuries to millennia to intentional landscape burning by people to maintain resources. We combine fieldwork, modeling, and a literature survey to examine the extent and mechanism by which anthropogenic burning alters the spatial grain of habitat mosaics in fire‐prone ecosystems. We survey the distribution of Callitris intratropica, a conifer requiring long fire‐free intervals for establishment, as an indicator of long‐unburned habitat availability under Aboriginal burning in the savannas of Arnhem Land. We then use cellular automata to simulate the effects of burning identical proportions of the landscape under different fire sizes on the emergent patterns of habitat heterogeneity. Finally, we examine the global extent of intentional burning and diversity of objectives using the scientific literature. The current distribution of Callitris across multiple field sites suggested long‐unburnt patches are common and occur at fine scales (<0.5 ha), while modeling revealed smaller, patchy disturbances maximize patch age diversity, creating a favorable habitat matrix for Callitris. The literature search provided evidence for intentional landscape burning across multiple ecosystems on six continents, with the number of identified objectives ranging from two to thirteen per study. The fieldwork and modeling results imply that the occurrence of long‐unburnt habitat in fire‐prone ecosystems may be an emergent property of patch scaling under fire regimes dominated by smaller fires. These findings provide a model for understanding how anthropogenic burning alters spatial and temporal aspects of habitat heterogeneity, which, as the literature survey strongly suggests, warrant consideration across a diversity of geographies and cultures. Our results clarify how traditional fire management shapes fire‐prone ecosystems, which despite diverse objectives, has allowed human societies to cope with fire as a recurrent disturbance.     

Comprehensive evaluation of multiple cropping systems on upland red soil

According to the principles and methods of ecology and system engineering, we set up an evaluation indicator system for multi-component and multiple cropping systems, evaluated the comprehensive benefits of multi-component and multiple cropping systems using grey relation clustering analysis and screened out the optimized model based on research done in the upland red soil in Jiangxi Agricultural University from 1984 to 2004. The results show that the grey relation degree of “cabbage/potato/maize — sesame” was the highest among 23 multi-component and multiple cropping systems and was clustered into the optimized system. This indicates that “cabbage/potato/maize — sesame” can bring the best social, economic and ecological benefits, increase product yield and farmers’ income and promote sustainable development of agricultural production. Therefore, it is suitable for promotion on upland red soil. The grey relation degree of “canola/Chinese milk vetch/maize/mung bean/maize” was second, which is suitable for implementation at the city outskirts. In conclusion, these two planting patterns are expected to play important roles in the reconstruction of the planting structure and optimization of the planting patterns on upland red soil. __________ Translated from Acta Ecologica Sinica, 2006, 26(8): 2532–2539 [译自: 生态学报]     

Environmental factors function as constraints on soil nitrous oxide fluxes in bioenergy feedstock cropping systems

Nitrous oxide (N₂O) is a potent greenhouse gas and major component of the net global warming potential of bioenergy feedstock cropping systems. Numerous environmental factors influence soil N₂O production, making direct correlation difficult to any one factor of N₂O fluxes under field conditions. We instead employed quantile regression to evaluate whether soil temperature, water‐filled pore space (WFPS), and concentrations of soil nitrate () and ammonium () determined upper bounds for soil N₂O flux magnitudes. We collected data over 6 years from a range of bioenergy feedstock cropping systems including no‐till grain crops, perennial warm‐season grasses, hybrid poplar, and polycultures of tallgrass prairie species each with and without nitrogen (N) addition grown at two sites. The upper bounds for soil N₂O fluxes had a significant and positive correlation with all four environmental factors, although relatively large fluxes were still possible at minimal values for nearly all factors. The correlation with was generally weaker, suggesting it is less important than in driving large fluxes. Quantile regression slopes were generally lower for unfertilized perennials than for other systems, but this may have resulted from a perpetual state of nitrogen limitation, which prevented other factors from being clear constraints. This framework suggests efforts to reduce concentrations of in the soil may be effective at reducing high‐intensity periods—”hot moments”—of N₂O production.     

Microbial metabolomics: toward a platform with full metabolome coverage

Achieving metabolome data with satisfactory coverage is a formidable challenge in metabolomics because metabolites are a chemically highly diverse group of compounds. Here we present a strategy for the development of an advanced analytical platform that allows the comprehensive analysis of microbial metabolomes. Our approach started with in silico metabolome information from three microorganisms-Escherichia coli, Bacillus subtilis, and Saccharomyces cerevisiae-and resulted in a list of 905 different metabolites. Subsequently, these metabolites were classified based on their physicochemical properties, followed by the development of complementary gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry methods, each of which analyzes different metabolite classes. This metabolomics platform, consisting of six different analytical methods, was applied for the analysis of the metabolites for which commercial standards could be purchased (399 compounds). Of these 399 metabolites, 380 could be analyzed with the platform. To demonstrate the potential of this metabolomics platform, we report on its application to the analysis of the metabolome composition of mid-logarithmic E. coli cells grown on a mineral salts medium using glucose as the carbon source. Of the 431 peaks detected, 235 (=176 unique metabolites) could be identified. These include 61 metabolites that were not previously identified or annotated in existing E. coli databases.     

不同分娩方式对产妇产后心理和生理的影响

目的:探讨不同分娩方式对产妇产后心理和生理的影响.方法:随机选择2011年1月～2011年12月在苏大附一院分娩的初产妇400例,其中剖宫产、阴道自然分娩各200例,对两组产妇产后42天心理状况、恶露持续时间、泌乳情况进行调查.结果:两种分娩方式对产妇产后42天发生焦虑和抑郁心理的影响无明显差别(P＞0.05);阴道自然分娩组产后恶露持续时间短于剖宫产组,差异有显著意义(P＜0.01).有抑郁、焦虑情绪的产妇泌乳始动时间显著长于正常产妇,24h泌乳量显著少于正常产妇(P＜0.01).结论:剖宫产对产妇身体生理创伤大过阴道自然分娩,应严格控制剖宫产的适应症,鼓励阴道自然分娩.     

丝状真菌代谢工程研究进展

丝状真菌(Filamentous fungi)作为重要的工业发酵微生物,在有机酸、蛋白质及次级代谢产物等关键生物基产品生产方面发挥着重要作用.自20世纪90年代代谢工程理念提出以来,尤其是代谢工程使能技术的创新及发展,极大地促进了丝状真菌细胞工厂的构建及其在工业发酵领域的应用.文中将系统介绍近年来丝状真菌代谢工程技术的...     

一类双线性生态系统的无源控制

研究了一类广义双线性系统的无源控制问题,利用广义Lyapunov函数和线性矩阵不等式,给出了广义双线性系统无源且零解渐近稳定的充分条件,并在一定条件下得到存在状态反馈控制器,使得闭环系统无源且零解渐近稳定的充分条件,同时给出相应的控制器构造方法。