外源微生物对木麻黄幼苗生长和土壤微生物群落的影响

将解淀粉芽孢杆菌(YB706)和伯克氏菌(BK8)外源添加至木麻黄盆栽苗中,运用Biolog生态板和磷脂脂肪酸(PLFA)技术,探究外施细菌能否改善连栽木麻黄土壤养分和微生物群落及植株生长。结果表明:与空白处理(CK)相比,YB706和BK8处理的木麻黄盆栽苗土壤碱解氮、速效磷显著增加,土壤全氮、全磷、全钾和速效钾无明显变化,幼苗株高分别增加59.1%和63.9%,BK8处理叶绿素含量提高81.9%。各处理平均颜色变化率(AWCD)呈现YB706>CK>BK8;除氨基酸类外,土壤微生物对不同碳源的利用率也表现为YB706>CK>BK8;经YB706和BK8处理的土壤微生物种类和数量均显著增加,除放线菌外,各类微生物PLFA总含量均为BK8>YB706>CK,与CK相比,土壤真菌/细菌有所提高。YB706和BK8处理的土壤微生物群落Simpson、Shannon、Brillouin和McIntosh指数均显著提高。表明外施YB706和BK8可促进木麻黄幼苗生长,且显著增加土壤速效养分含量,提高土壤微生物群落结构多样性,改善土壤微生物环境。     

不同水位时期东洞庭湖湿地土壤微生物生物量碳氮和酶活性变化

为从土壤微生物的角度分析东洞庭湖不同植被类型湿地土壤质量状况,本研究选取了苔草、芦苇和柳树3种典型植被类型为对象,在平水期、丰水期和枯水期对其土壤微生物生物量碳(MBC)、氮(MBN)和酶活性进行监测,并分析其主要影响因子。结果表明: 1)3个水位时期,各植被类型湿地土壤MBC、MBN、蔗糖酶和纤维素酶活性(枯水期纤维素酶除外)均表现为0～10 cm高于10～20 cm,而土壤过氧化氢酶活性则相反。2)各植被类型湿地0～20 cm土层土壤MBC、MBN和MBC/TOC(总有机碳)、MBN/TN(总氮)皆以丰水期最低。3)各植被类型湿地0～20 cm土层土壤蔗糖酶活性峰值均出现在枯水期,而纤维素酶活性峰值出现在平水期,过氧化氢酶活性季节性波动较小,以丰水期稍高。4)不同植被类型间比较:平水期和丰水期,芦苇湿地土壤蔗糖酶活性显著高于其他植被类型,而其土壤纤维素酶活性最低,枯水期不同湿地间两种酶活性差异不显著。土壤过氧化氢酶活性在平水期以苔草湿地最高,枯水期以柳树湿地最高,丰水期以芦苇湿地最低。5)相关性分析表明,土壤MBC、MBN和蔗糖酶与TOC、TN、总磷(TP)呈显著正相关,而与pH值呈显著负相关。土壤纤维素酶和过氧化氢酶与TOC、TN、TP呈显著负相关,与pH值呈显著正相关。表明季节性水位波动影响土壤C、N、P和pH值,并对土壤微生物生物量碳、氮和酶活性产生显著影响,使其呈现明显的季节性变化特征。     

黄山松土壤可溶性有机质对氮添加的响应及其与细菌群落的关联

为探究黄山松土壤可溶性有机质(DOM)数量和质量对短期氮(N)添加的响应及其与细菌群落的关联,在福建戴云山自然保护区设置不同N添加水平(0、40和80 kg N·hm^-2·a^-1)试验,采用三维荧光与平行因子联用法,并结合高通量测序手段分别对土壤DOM和细菌群落进行分析。结果表明: 与对照相比,N添加整体降低了0～10和10～20 cm土层可溶性有机碳(DOC)含量和DOM腐殖化指数(HIX),其中,高氮(80 kg N·hm^-2·a^-1)添加下均显著降低。平行因子分析法进一步表明N添加下DOM中类腐殖质组分(C1、C2)的相对含量降低。此外,N添加减少了富营养细菌(变形菌门、酸微菌纲)的相对丰度,而增加了贫营养细菌(斯巴达杆菌纲)的相对丰度。富营养细菌的相对丰度与HIX、C1、C2呈显著正相关,与相对易分解的类富里酸组分(C3)呈显著负相关;而贫营养细菌的情况则相反。说明N添加下不同生活策略的细菌类群对DOM中难分解和易分解组分存在明显的偏好性。我们推测N沉降加剧背景下土壤微生物生活策略的转变可能有助于DOM组分的塑造。     

Effects of Different Ambient Temperatures on Caecal Microbial Composition in Broilers

Short-term or acute temperature stress affect the immune responses and alters the gut microbiota of broilers, but the influences of long-term temperature stress on stress biomarkers and the intestinal microbiota remains largely unknown. Therefore, we examined the effect of three long-term ambient temperatures (high (HC), medium (MC), and low (LC) temperature groups) on the gene expression of broilers’ heat shock proteins (Hsps) and inflammation – related genes, as well as the caecal microbial composition. The results revealed that Hsp70 and Hsp90 levels in HC group significantly increased, and levels of Hsp70, Hsp90, IL-6, TNF-α, and NFKB1 in LC group were significantly higher than in MC group (p < 0.05). In comparison with the MC group, the proportion of Firmicutes increased in HC and LC groups, while that of Bacteroidetes decreased in LC group at phylum level (p < 0.05). At genus level, the proportion of Escherichia/Shigella, Phascolarctobacterium, Parabacteroides,and Enterococcus increased in HC group; the fraction of Faecalibacterium was higher in LC group; and the percentage of Barnesiella and Alistipes decreased in both HC and LC groups (p < 0.05). Functional analysis based on communities’ phylogenetic investigation revealed that the pathways involved in environmental information processing and metabolism were enriched in the HC group. Those involved in cellular processes and signaling, metabolism, and gene regulation were enriched in LC group. Hence, we conclude that the long-term temperature stress can greatly alter the intestinal microbial communities in broilers and may further affect the host’s immunity and health.     

兰州兴隆山土壤微生物的分布及其相关特性分析

目的以兰州兴隆山不同区域的土壤微生物为研究对象,分析比较土壤微生物数量与土壤酶活性之间的相关性。方法利用不同方法测定土壤理化性质、微生物数量以及土壤相关酶活特性;采用三区划线法进行土壤微生物的分离与纯化,通过16S rDNA和ITS方法进行优势菌株鉴定。结果兰州兴隆山土壤中微生物菌群数量由多到少依次为细菌、放线菌、真菌。通过分离纯化后,对其中的2株优势菌进行了鉴定,初步推断X2为萎缩芽胞杆菌属(Bacillus atrophaeus)细菌,Z2为栎生青霉属(Penicillium glandicola)真菌。从酶活特性可知,阳面的土壤过氧化氢酶活性比阴面高;随着海拔高度的增加,过氧化氢酶活性呈现增加趋势;阳面的土壤脱氢酶活性总体比阴面高,并且随着海拔梯度的升高,土壤脱氢酶活性也在不断升高。从相关性分析可知,不同海拔土样间微生物数量与酶活性之间表现出明显的相关性。结论兰州兴隆山土壤微生物数量丰富,且细菌数量居多;不同阴、阳面土壤微生物的层次分布以及活性也各有不同。以上研究可为兰州兴隆山土壤生态系统演替等提供参考依据,并为土壤生态环境的治理做铺垫。     

Forest Saccharomyces paradoxus are robust to seasonal biotic and abiotic changes

Microorganisms are famous for adapting quickly to new environments. However, most evidence for rapid microbial adaptation comes from laboratory experiments or domesticated environments, and it is unclear how rates of adaptation scale from human‐influenced environments to the great diversity of wild microorganisms. We examined potential monthly‐scale selective pressures in the model forest yeast Saccharomyces paradoxus. Contrary to expectations of seasonal adaptation, the S. paradoxus population was stable over four seasons in the face of abiotic and biotic environmental changes. While the S. paradoxus population was diverse, including 41 unique genotypes among 192 sampled isolates, there was no correlation between S. paradoxus genotypes and seasonal environments. Consistent with observations from other S. paradoxus populations, the forest population was highly clonal and inbred. This lack of recombination, paired with population stability, implies that selection is not acting on the forest S. paradoxus population on a seasonal timescale. Saccharomyces paradoxus may instead have evolved generalism or phenotypic plasticity with regard to seasonal environmental changes long ago. Similarly, while the forest population included diversity among phenotypes related to intraspecific interference competition, there was no evidence for active coevolution among these phenotypes. At least ten percent of the forest S. paradoxus individuals produced “killer toxins,” which kill sensitive Saccharomyces cells, but the presence of a toxin‐producing isolate did not predict resistance to the toxin among nearby isolates. How forest yeasts acclimate to changing environments remains an open question, and future studies should investigate the physiological responses that allow microbial cells to cope with environmental fluctuations in their native habitats.     

Preparation of optically active 4-chlorophenylalanine from its racemate by deracemization technique using transformant Escherichia coli cells

We have developed a method for the preparation of l-4-chlorophenylalanine from its racemate with Escherichia coli cells expressing a single foreign gene. l-4-Chlorophenylalanine was obtained in a high optical yield by the inversion of configuration of its d-form via the tandem reactions catalyzed by d-amino acid dehydrogenase (DadA) and branched-chain amino acid aminotransferase (BCAAT). While we constructed a plasmid for BCAAT utilizing the gene from Sinorhizobium meliloti ATCC 51124, the first enzyme DadA was the dadA-gene product from E. coli host cell itself, which was activated by the addition of l-alanine in the growth medium.     

Stereocontrolled Reduction of Alpha-Methyl Beta-Ketoesters by Geotrichum Candidum

The conditions of the reduction of racemic ethyl 2-methyi-3-oxobutanoate by the mould Geotrichum candidum have been investigated in order to produce exclusively the corresponding (2S, 3S) anti hydroxyester. The alteration of the syn/anti hydroxyester ratio previously observed is the result of an interconversion equilibrium involving the oxoester. The syn ester formation is inhibited by ageing the biomass in water before use, or by effecting the reduction in the presence of sodium chloride. Optimized conditions are described allowing the production of the anti ester in high yield and high optical purity.     

Towards a Molecular Taxonomy for Protists: Benefits,Risks, and Applications in Plankton Ecology

The increasing use of genetic information for the development of methods to study the diversity, distributions, and activities of protists in nature has spawned a new generation of powerful tools. For ecologists, one lure of these approaches lies in the potential for DNA sequences to provide the only immediately obvious means of normalizing the diverse criteria that presently exist for identifying and counting protists. A single, molecular taxonomy would allow studies of diversity across a broad range of species, as well as the detection and quantification of particular species of interest within complex, natural assemblages; goals that are not feasible using traditional methods. However, these advantages are not without their potential pitfalls and problems. Conflicts involving the species concept, disagreements over the true (physiological/ecological) meaning of genetic diversity, and a perceived threat by some that sequence information will displace knowledge regarding the morphologies, functions and physiologies of protistan taxa, have created debate and doubt regarding the efficacy and appropriateness of some genetic approaches. These concerns need continued discussion and eventual resolution as we move toward the irresistible attraction, and potentially enormous benefits, of the application of genetic approaches to protistan ecology.     

A STUDY OF ABANDONED ASH PONDS RECLAIMED THROUGH GREEN COVER DEVELOPMENT

Green capping is one of the popular methods to re-vegetate abandoned ash ponds of coal based thermal power plants thereby lowering the risk of contamination to the surrounding environment. It has innumerable advantages such as prevention of dust emission, checking soil erosion, stabilizing the surface areas of ash, preventing potential ground water contamination, and finally, adding native vegetation cover, which is very vital in the long term. During the early nineties and later, various reclamation projects were carried out on fly ash dumps, but until date, there have not been any initiatives to assess the alterations in physicochemical and biological properties of fly ash resulting from implementation of these reclamation projects. In the present study, three abandoned ash ponds, located in India, that were reclaimed during 1998–2003 are investigated. Marked alterations in nutritional status, microbial population, and microbial activities have been observed in reclaimed ash ponds.