The characterization of microbial communities of different depth sediment samples was examined by a culture-independent method and compared with physicochemical parameters, those are organic matter （OM）, total nitro...The characterization of microbial communities of different depth sediment samples was examined by a culture-independent method and compared with physicochemical parameters, those are organic matter （OM）, total nitrogen （TN）, total phosphorus （TP）, pH and redox potential （Eh）. Total genomic DNA was extracted from samples derived from different depths. After they were amplified with the GC-341 f/907r primer sets of partial bacterial 16S rRNA genes, the products were separated by denaturing gradient gel electrophoresis （DGGE）. The profile of DGGE fingerprints of different depth sediment samples revealed that the community structure remained relatively stable along the entire 45 cm sediment core, however, principal-component analysis of DGGE patterns revealed that at greater sediment depths, successional shifts in community structure were evident. The principle coordinates analysis suggested that the bacterial communities along the sediment core could be separated into two groups, which were located 0-20 cm and 21-45 cm, respectively. The sequencing dominant bands demonstrated that the major phylogenetic groups identified by DGGE belonged to Bacillus, Bacterium, Brevibacillus, Exiguobacterium, γ-Proteobacterium, Acinetobacter sp. and some uncultured or unidentified bacteria. The results indicated the existence of highly diverse bacterial community in the lake sediment core.展开更多
Information on co-adherence of different oral bacterial species is important for understanding interspecies interactions within oral microbial community. Current knowledge on this topic is heavily based on pariwise co...Information on co-adherence of different oral bacterial species is important for understanding interspecies interactions within oral microbial community. Current knowledge on this topic is heavily based on pariwise coaggregation of known, cultivable species. In this study, we employed a membrane binding assay coupled with polymerase chain reaction-denaturing gradient gel electrophoresis （PCR-DGGE） to systematically analyze the co-adherence profiles of oral bacterial species, and achieved a more profound knowledge beyond pairwise coaggregation. Two oral bacterial species were selected to serve as ＂bait＂： Fusobacterium nucleatum （F. nucleatum） whose ability to adhere to a multitude of oral bacterial species has been extensively studied for pairwise interactions and Streptococcus mutans （S. mutans） whose interacting partners are largely unknown. To enable screening of interacting partner species within bacterial mixtures, cells of the ＂bait＂ oral bacterium were immobilized on nitrocellulose membranes which were washed and blocked to prevent unspecific binding. The ＂prey＂ bacterial mixtures （including known species or natural saliva samples） were added, unbound ceils were washed off after the incubation period and the remaining cells were eluted using 0.2 mol.L1 glycine. Genomic DNA was extraeted, subjeeted to 16S rRNA PCR amplification and separation of the resulting PCR produets by DGGE. Selected bands were recovered from the gel, sequenced and identified via Nucleotide BLAST searches against different databases. While few bacterial species bound to S. mutans, consistent with previous findings F.. nucleatum adhered to a variety of bacterial species including uncultivable and uneharacterized onesl This new approach can more effectively analyze the co-adherence profiles of oral bacteria, and could facilitate the systematic study of interbacterial binding of oral microbial species.展开更多
Bacterial diversity was investigated in soil samples collected from 13 sites around the Great Wall Station, Fildes Peninsula, King George Island, Antarctica, using denaturing gradient gel electrophoresis （DGGE） of 1...Bacterial diversity was investigated in soil samples collected from 13 sites around the Great Wall Station, Fildes Peninsula, King George Island, Antarctica, using denaturing gradient gel electrophoresis （DGGE） of 16S rRNA genes. The classes α-, β-, and γ-Proteobacteria, as well as the phylum Actinobacteria, were found to be the dominant bacteria in the soils around the Great Wall Station. Although the selected samples were not contaminated by oil, a relationship between soil parameters, microbial biodiversity, and human impact was still seen. Sample sites in human impacted areas showed lower bacterial biodiversity （average H′= 2.65） when compared to nonimpacted sites （average H′= 3.05）. There was no statistically significant correlation between soil bacterial diversity and total organic carbon （TOC）, total nitrogen, or total phosphorus contents of the soil. Canonical correlation analysis showed that TOC content was the most important factor determining bacterial community profiles among the measured soil parameters. In conclusion, microbial biodiversity and community characteristics within relatively small scales （1.5 km） were determined as a function of local environment parameters and anthropogenic impact.展开更多
The actinomycete populations and functions in cadmium （Cd） contaminated soil were investigated by the cultivation- independent molecular methods. The genomic DNA was extracted and purified from soil adulterated with...The actinomycete populations and functions in cadmium （Cd） contaminated soil were investigated by the cultivation- independent molecular methods. The genomic DNA was extracted and purified from soil adulterated with various con- centrations of Cd in the laboratory. The partial 16S rDNA genes were amplified by polymerase chain reaction （PCR） using specific primers bound to evolutionarily conserved regions within these actinomycete genes. The diversity in PCR- amplified products, as measured by denaturing gradient gel electrophoresis （EGGE）, was used as a genetic fingerprint of the population. Principle component analysis and Shannon-Weaver diversity index （H） analyses were used to analyze the DGGE results. Results showed that the two principal components accounted for only a low level of the total variance. The value H in contaminated soil was lower than that in the control at later stages of cultivation, whereas at earlier stages it was higher. Among the six sampling time points, the first, fifth and sixth weeks had the highest values of H. Significantly negative correlations between bioavallable Cd concentration and H values existed in the samples from weeks 2 （R = 0.929, P 〈 0.05） and 4 （R = 0.909, P 〈 0.05）. These results may shed light on the effect of Cd on the soil environment and the chemical behavior and toxicity of Cd to actinomycetes.展开更多
To study the structure of microbial communities in the biological hydrogen produc-tion reactor and determine the ecological function of hydrogen producing bacteria,anaerobic sludge was obtained from the continuous sti...To study the structure of microbial communities in the biological hydrogen produc-tion reactor and determine the ecological function of hydrogen producing bacteria,anaerobic sludge was obtained from the continuous stirred tank reactor(CSTR)in different periods of time,and the diversity and dynamics of microbial communities were investigated by denaturing gra-dient gel electrophoresis(DGGE).The results of DGGE demonstrated that an obvious shift of microbial population happened from the beginning of star-up to the 28th day,and the ethanol type fermentation was established.After 28 days the structure of microbial community became stable,and the climax community was formed.Comparative analysis of 16S rDNA sequences from reamplifying and sequencing the prominent bands indicated that the dominant population belonged to low G+C Gram-positive bacteria(Clostridium sp.and Ethanologenbacterium sp.),β-proteobacteria(Acidovorax sp.),γ-proteobacteria(Kluyvera sp.),Bacteroides(uncultured bacte-rium SJA-168),and Spirochaetes(uncultured eubacterium E1-K13),respectively.The hydrogen production rate increased obviously with the increase of Ethanologenbacterium sp.,Clostridium sp.and uncultured Spirochaetes after 21 days,meanwhile the succession of ethanol type fer-mentation was formed.Throughout the succession the microbial diversity increased however it decreased after 21 days.Some types of Clostridium sp.Acidovorax sp.,Kluyvera sp.,and Bac-teroides were dominant populations during all periods of time.These special populations were essential for the construction of climax community.Hydrogen production efficiency was de-pendent on both hydrogen producing bacteria and other populations.It implied that the co-metabolism of microbial community played a great role of biohydrogen production in the reactors.展开更多
Functional gradient materials provided us a new concept for artificial articular cartilage design with gradient component and gradient structure where one side of the material is high free water content thereby provid...Functional gradient materials provided us a new concept for artificial articular cartilage design with gradient component and gradient structure where one side of the material is high free water content thereby providing excellent lubrication function and the opposite side of the material is high hydroxyapatite content, thereby improving the bioactivity of the material and stimulating cell growth. The goal of the present study was to develop a multi-layered gradient HA/PVA gel biocomposites through layer-by-layer casting method combing with freeze/thaw cycle technology. The various influence factors on the compressive strength and modulus of the multi-layered gradient biocomposites were investigated. The results showed that the compressive mechanical characteristics of the biocomposites were similar to that of natural articular cartilage. Both the compressive strength and modulus of the multi-layered gradient HA/PVA gel biocomposites increased exponentially with the rise of compressive strain ratio. Both the compressive strength and average compressive modulus of the biocomposites improved with the rise of freeze/thaw cycle times and total concentration of HA particles in the biocomposites, but they showed decreasing tendency with the rise of HA concentration difference between adjacent layers.展开更多
To better understand the effect of salinity on denitrification communities, soils along a salinity gradient （ranging from 7.32 to 1.70 mS cm 1） in a wetland along the Yellow Sea coastline in Jiangsu Province, China,...To better understand the effect of salinity on denitrification communities, soils along a salinity gradient （ranging from 7.32 to 1.70 mS cm 1） in a wetland along the Yellow Sea coastline in Jiangsu Province, China, were studied using both culture-dependent and -independent methods. Culture efforts yielded 82 isolates in total, 81.7% of which were close relatives of Bacillus sp. based on partial sequences of their 16S rRNA genes. Denaturing gradient gel electrophoresis （DGGE） analysis based on 16S rRNA sequences suggested possible existence of bacterial community succession along the salinity gradient. Clone library analysis based on nosZ gene sequences （coding nitrous oxide reductase） showed that operational taxonomic units （OTUs） associated with α-proteobacteria dominated in all three soils, whereas those associated with β- and γ-subdivisions showed a clear succession. In the high salinity soil, only the OTUs associated with a-subdivision were found. In the medium salinity soil, small proportions of β- （6.5%） and γ-associated （19.6%） OTUs were found. In the low salinity soil, the proportions were further increased to 33% and 25% for β- and γ-Proteobacteria, respectively. Statistic analysis using Unifrac P test showed that nosZ-communities in different saline soils were significantly different from each other. It could be concluded that α-subdivision of nosZ-community tended to be sustained in high salinity environments whereas β and γ-subdivisions, especially the former, tended to be sustained in low salinity environments. Salinity was the key determinant of nosZ-community composition in the environment.展开更多
Compositional graded BaxSr1-xTiO3 (x=0.6, 0.7, 0.8, 0.9, 1.0) (BST) thin films (less than 400 nm) were fabricated on Si and Pt/Ti/SiO2/Si substrates by sol-gel technique. A special heating treatment was employed to fo...Compositional graded BaxSr1-xTiO3 (x=0.6, 0.7, 0.8, 0.9, 1.0) (BST) thin films (less than 400 nm) were fabricated on Si and Pt/Ti/SiO2/Si substrates by sol-gel technique. A special heating treatment was employed to form the uniform composition gradients at 700 ℃. The microstructures of the films were studied by means of X-ray diffraction, atomic force microscope and field emission scanning electron microscopy. The results show that the films have uniform and crack-free surface morphology with perovskite structure phase. The small signal dielectric constant (εr) and dielectric loss (tan δ) are found to be 335 and 0.045 at room temperature and 200 kHz. The dielectric properties change significantly with applied dc bias, and the graded thin film show high tunability of 42.3% at an applied field of 250 kV/cm. All the results indicate that the graded BST thin films prepared by sol-gel technique have a promising candidate for microelectronic device.展开更多
【目的】比较新一代高通量测序与传统的变性梯度凝胶电泳(Denaturing Gradient Gel Electrophoresis,DGGE)指纹图谱技术,评价两种技术研究土壤微生物群落结构的优缺点。【方法】针对新西兰典型草地和森林土壤,以16S rRNA基因为标靶,通...【目的】比较新一代高通量测序与传统的变性梯度凝胶电泳(Denaturing Gradient Gel Electrophoresis,DGGE)指纹图谱技术,评价两种技术研究土壤微生物群落结构的优缺点。【方法】针对新西兰典型草地和森林土壤,以16S rRNA基因为标靶,通过高通量测序和DGGE技术分析土壤微生物群落的组成、丰度和多样性,比较两种方法在土壤微生物研究中的适用性。【结果】在不同的微生物分类水平,高通量测序草地土壤检测到22门,54纲,60目,131科,350属;而DGGE仅检测到6门,9纲,8目,10科,10属,表明DGGE显著低估了土壤微生物的群落组成。森林土壤也得到了类似规律,高通量测序的检测灵敏度是DGGE的3.8、6.7、6.4、19.2及39.4倍。进一步分析土壤中主要微生物类群的相对丰度,发现分类水平越低,高通量测序与DGGE的结果差异越大,尤其在科和属的水平上差异最大。以高通量测序结果为标准,DGGE明显高估了土壤中大多数微生物类群的相对丰度,最高可达2000倍。两种方法都表明草地土壤的多样性指数高于森林土壤,但DGGE多样性指数的绝对值远低于高通量测序结果。【结论】高通量测序能够较为全面和准确的反映土壤微生物群落结构,而DGGE仅能够反映有限的优势微生物类群,在很大程度上极可能低估土壤微生物的物种组成并高估其丰度。展开更多
To know the bacterial communities structure in Babylonia areolata culture systems and to research and optimize the management pattem of Babylonia areola-ta culture systems of the pond mulched plastic film and sand in ...To know the bacterial communities structure in Babylonia areolata culture systems and to research and optimize the management pattem of Babylonia areola-ta culture systems of the pond mulched plastic film and sand in bottom, the bacte- rial communities in Babylonia areolata culture systems of the sub-tidal zone and the pond mulched plastic film and sand in bottom were analyzed at molecular level by adopting the denaturing gradient gel electrophoresis （DGGE）. The results indicated that the dominant bacterial communities in Babylonia areolata culture systems of the sub-tidal zone and the pond mulched plastic film and sand in bottom, which were built on the basis of the seawater in East-island of Zhanjiang, included Proteobac- teda Chloroflexi, Cyanobacteria and Actinobacteria. The dominant bacterial groups in the above pond culture system were Garnmaproteobacteria, Alphaproteobacteria, Deltaprotecbacteda, Epsilonproteobacteda, Anaerolineae, Cyanobacteria and Acti- nobacteda. The dominant bacterial communities in the subtidal zone culture system were Gammaprotecbacteda, Alphaproteobacteria, Deltaproteobacteria, Anaerolineae and Cyanobacteda, and there were less Epsilonproteobacteria and Actinobacteria in the culture system. The higher diversity was detected in the above two culture sys- tems. The results of unweighted pair group method with arithmetic average （UPG- MA） showed that the bacterial communities of the sediment samples S1 and S2 in the above two culture systems were a cluster, the similarity of bacterial communities was 54.5%. The bacterial communities of seawater samples S3 and S4 in the above culture systems were in clusters, and the similarity of the bacterial communi- ties was 84.0%. The results showed that the microorganism ecological level in the Babylonia areolata culture systems of the pond mulched plastic film and sand in bottom could be similar to the sub-tidal zone culture systems through changing the pond seawater and monitoring the microbial population.展开更多
基金This work was supported by the National Basic Research Program （973） of China （No. 2002CB412307） the Hi-Tech Research and Development Program （863） of China （No. 2002AA601011） the National Natural Science Foundation of China （No. 40371102）.
文摘The characterization of microbial communities of different depth sediment samples was examined by a culture-independent method and compared with physicochemical parameters, those are organic matter （OM）, total nitrogen （TN）, total phosphorus （TP）, pH and redox potential （Eh）. Total genomic DNA was extracted from samples derived from different depths. After they were amplified with the GC-341 f/907r primer sets of partial bacterial 16S rRNA genes, the products were separated by denaturing gradient gel electrophoresis （DGGE）. The profile of DGGE fingerprints of different depth sediment samples revealed that the community structure remained relatively stable along the entire 45 cm sediment core, however, principal-component analysis of DGGE patterns revealed that at greater sediment depths, successional shifts in community structure were evident. The principle coordinates analysis suggested that the bacterial communities along the sediment core could be separated into two groups, which were located 0-20 cm and 21-45 cm, respectively. The sequencing dominant bands demonstrated that the major phylogenetic groups identified by DGGE belonged to Bacillus, Bacterium, Brevibacillus, Exiguobacterium, γ-Proteobacterium, Acinetobacter sp. and some uncultured or unidentified bacteria. The results indicated the existence of highly diverse bacterial community in the lake sediment core.
基金supported by Chinese State Scholarship Fund to R. WangUS National Institutes of Health (NIH) Grants DE020102 and GM95373 to W. Shi
文摘Information on co-adherence of different oral bacterial species is important for understanding interspecies interactions within oral microbial community. Current knowledge on this topic is heavily based on pariwise coaggregation of known, cultivable species. In this study, we employed a membrane binding assay coupled with polymerase chain reaction-denaturing gradient gel electrophoresis （PCR-DGGE） to systematically analyze the co-adherence profiles of oral bacterial species, and achieved a more profound knowledge beyond pairwise coaggregation. Two oral bacterial species were selected to serve as ＂bait＂： Fusobacterium nucleatum （F. nucleatum） whose ability to adhere to a multitude of oral bacterial species has been extensively studied for pairwise interactions and Streptococcus mutans （S. mutans） whose interacting partners are largely unknown. To enable screening of interacting partner species within bacterial mixtures, cells of the ＂bait＂ oral bacterium were immobilized on nitrocellulose membranes which were washed and blocked to prevent unspecific binding. The ＂prey＂ bacterial mixtures （including known species or natural saliva samples） were added, unbound ceils were washed off after the incubation period and the remaining cells were eluted using 0.2 mol.L1 glycine. Genomic DNA was extraeted, subjeeted to 16S rRNA PCR amplification and separation of the resulting PCR produets by DGGE. Selected bands were recovered from the gel, sequenced and identified via Nucleotide BLAST searches against different databases. While few bacterial species bound to S. mutans, consistent with previous findings F.. nucleatum adhered to a variety of bacterial species including uncultivable and uneharacterized onesl This new approach can more effectively analyze the co-adherence profiles of oral bacteria, and could facilitate the systematic study of interbacterial binding of oral microbial species.
基金supported by the National Natural Science Foundation of China (No. 51108331)the Chinese Polar Environment Comprehensive Investigation and Assessment Programmes (No. CHINARE2012-02-01-08, CHINARE2013-02-01-08, CHINARE2013-04-01-07)
文摘Bacterial diversity was investigated in soil samples collected from 13 sites around the Great Wall Station, Fildes Peninsula, King George Island, Antarctica, using denaturing gradient gel electrophoresis （DGGE） of 16S rRNA genes. The classes α-, β-, and γ-Proteobacteria, as well as the phylum Actinobacteria, were found to be the dominant bacteria in the soils around the Great Wall Station. Although the selected samples were not contaminated by oil, a relationship between soil parameters, microbial biodiversity, and human impact was still seen. Sample sites in human impacted areas showed lower bacterial biodiversity （average H′= 2.65） when compared to nonimpacted sites （average H′= 3.05）. There was no statistically significant correlation between soil bacterial diversity and total organic carbon （TOC）, total nitrogen, or total phosphorus contents of the soil. Canonical correlation analysis showed that TOC content was the most important factor determining bacterial community profiles among the measured soil parameters. In conclusion, microbial biodiversity and community characteristics within relatively small scales （1.5 km） were determined as a function of local environment parameters and anthropogenic impact.
基金Project supported by the National Natural Science Foundation of China (Nos. 30570053 and 40501037)the National High Technology Research and Development Program (863 Program) of China (No. 2007AA10Z409)+1 种基金the National"Eleventh Five Years Plan" Key Project on Science and Technology of China (No. 2006BAJ08B01)the Research Fund of Science and Technology Bureau of Zhejiang Province,China (No. 2008C23088)
文摘The actinomycete populations and functions in cadmium （Cd） contaminated soil were investigated by the cultivation- independent molecular methods. The genomic DNA was extracted and purified from soil adulterated with various con- centrations of Cd in the laboratory. The partial 16S rDNA genes were amplified by polymerase chain reaction （PCR） using specific primers bound to evolutionarily conserved regions within these actinomycete genes. The diversity in PCR- amplified products, as measured by denaturing gradient gel electrophoresis （EGGE）, was used as a genetic fingerprint of the population. Principle component analysis and Shannon-Weaver diversity index （H） analyses were used to analyze the DGGE results. Results showed that the two principal components accounted for only a low level of the total variance. The value H in contaminated soil was lower than that in the control at later stages of cultivation, whereas at earlier stages it was higher. Among the six sampling time points, the first, fifth and sixth weeks had the highest values of H. Significantly negative correlations between bioavallable Cd concentration and H values existed in the samples from weeks 2 （R = 0.929, P 〈 0.05） and 4 （R = 0.909, P 〈 0.05）. These results may shed light on the effect of Cd on the soil environment and the chemical behavior and toxicity of Cd to actinomycetes.
基金This work was supported by the National Science Foundation for Distinguished Young Scholars(No.50125823)National Natural Science Foundation of China(Grant No.30470054)Key Project of Chinese National Programs for Fundamental Research and Development(No.G2000026402).
文摘To study the structure of microbial communities in the biological hydrogen produc-tion reactor and determine the ecological function of hydrogen producing bacteria,anaerobic sludge was obtained from the continuous stirred tank reactor(CSTR)in different periods of time,and the diversity and dynamics of microbial communities were investigated by denaturing gra-dient gel electrophoresis(DGGE).The results of DGGE demonstrated that an obvious shift of microbial population happened from the beginning of star-up to the 28th day,and the ethanol type fermentation was established.After 28 days the structure of microbial community became stable,and the climax community was formed.Comparative analysis of 16S rDNA sequences from reamplifying and sequencing the prominent bands indicated that the dominant population belonged to low G+C Gram-positive bacteria(Clostridium sp.and Ethanologenbacterium sp.),β-proteobacteria(Acidovorax sp.),γ-proteobacteria(Kluyvera sp.),Bacteroides(uncultured bacte-rium SJA-168),and Spirochaetes(uncultured eubacterium E1-K13),respectively.The hydrogen production rate increased obviously with the increase of Ethanologenbacterium sp.,Clostridium sp.and uncultured Spirochaetes after 21 days,meanwhile the succession of ethanol type fer-mentation was formed.Throughout the succession the microbial diversity increased however it decreased after 21 days.Some types of Clostridium sp.Acidovorax sp.,Kluyvera sp.,and Bac-teroides were dominant populations during all periods of time.These special populations were essential for the construction of climax community.Hydrogen production efficiency was de-pendent on both hydrogen producing bacteria and other populations.It implied that the co-metabolism of microbial community played a great role of biohydrogen production in the reactors.
基金the financial support from the National Natural Science Foundation of China (No.51175004)the Natural Science Research of Key Projects of Anhui Provincial Universities(No.KJ2010A099)
文摘Functional gradient materials provided us a new concept for artificial articular cartilage design with gradient component and gradient structure where one side of the material is high free water content thereby providing excellent lubrication function and the opposite side of the material is high hydroxyapatite content, thereby improving the bioactivity of the material and stimulating cell growth. The goal of the present study was to develop a multi-layered gradient HA/PVA gel biocomposites through layer-by-layer casting method combing with freeze/thaw cycle technology. The various influence factors on the compressive strength and modulus of the multi-layered gradient biocomposites were investigated. The results showed that the compressive mechanical characteristics of the biocomposites were similar to that of natural articular cartilage. Both the compressive strength and modulus of the multi-layered gradient HA/PVA gel biocomposites increased exponentially with the rise of compressive strain ratio. Both the compressive strength and average compressive modulus of the biocomposites improved with the rise of freeze/thaw cycle times and total concentration of HA particles in the biocomposites, but they showed decreasing tendency with the rise of HA concentration difference between adjacent layers.
基金Supported by the National Natural Science Foundation of China (No. 41071177)
文摘To better understand the effect of salinity on denitrification communities, soils along a salinity gradient （ranging from 7.32 to 1.70 mS cm 1） in a wetland along the Yellow Sea coastline in Jiangsu Province, China, were studied using both culture-dependent and -independent methods. Culture efforts yielded 82 isolates in total, 81.7% of which were close relatives of Bacillus sp. based on partial sequences of their 16S rRNA genes. Denaturing gradient gel electrophoresis （DGGE） analysis based on 16S rRNA sequences suggested possible existence of bacterial community succession along the salinity gradient. Clone library analysis based on nosZ gene sequences （coding nitrous oxide reductase） showed that operational taxonomic units （OTUs） associated with α-proteobacteria dominated in all three soils, whereas those associated with β- and γ-subdivisions showed a clear succession. In the high salinity soil, only the OTUs associated with a-subdivision were found. In the medium salinity soil, small proportions of β- （6.5%） and γ-associated （19.6%） OTUs were found. In the low salinity soil, the proportions were further increased to 33% and 25% for β- and γ-Proteobacteria, respectively. Statistic analysis using Unifrac P test showed that nosZ-communities in different saline soils were significantly different from each other. It could be concluded that α-subdivision of nosZ-community tended to be sustained in high salinity environments whereas β and γ-subdivisions, especially the former, tended to be sustained in low salinity environments. Salinity was the key determinant of nosZ-community composition in the environment.
基金Project(50372017/E0204) supported by the National Natural Science Foundation of China Project (2004ABA094) supported by the Natural Science Foundation of Hubei Province Project supported by the Innovation Team Foundation of Education Bureau of Hubei Province, China
文摘Compositional graded BaxSr1-xTiO3 (x=0.6, 0.7, 0.8, 0.9, 1.0) (BST) thin films (less than 400 nm) were fabricated on Si and Pt/Ti/SiO2/Si substrates by sol-gel technique. A special heating treatment was employed to form the uniform composition gradients at 700 ℃. The microstructures of the films were studied by means of X-ray diffraction, atomic force microscope and field emission scanning electron microscopy. The results show that the films have uniform and crack-free surface morphology with perovskite structure phase. The small signal dielectric constant (εr) and dielectric loss (tan δ) are found to be 335 and 0.045 at room temperature and 200 kHz. The dielectric properties change significantly with applied dc bias, and the graded thin film show high tunability of 42.3% at an applied field of 250 kV/cm. All the results indicate that the graded BST thin films prepared by sol-gel technique have a promising candidate for microelectronic device.
文摘【目的】比较新一代高通量测序与传统的变性梯度凝胶电泳(Denaturing Gradient Gel Electrophoresis,DGGE)指纹图谱技术,评价两种技术研究土壤微生物群落结构的优缺点。【方法】针对新西兰典型草地和森林土壤,以16S rRNA基因为标靶,通过高通量测序和DGGE技术分析土壤微生物群落的组成、丰度和多样性,比较两种方法在土壤微生物研究中的适用性。【结果】在不同的微生物分类水平,高通量测序草地土壤检测到22门,54纲,60目,131科,350属;而DGGE仅检测到6门,9纲,8目,10科,10属,表明DGGE显著低估了土壤微生物的群落组成。森林土壤也得到了类似规律,高通量测序的检测灵敏度是DGGE的3.8、6.7、6.4、19.2及39.4倍。进一步分析土壤中主要微生物类群的相对丰度,发现分类水平越低,高通量测序与DGGE的结果差异越大,尤其在科和属的水平上差异最大。以高通量测序结果为标准,DGGE明显高估了土壤中大多数微生物类群的相对丰度,最高可达2000倍。两种方法都表明草地土壤的多样性指数高于森林土壤,但DGGE多样性指数的绝对值远低于高通量测序结果。【结论】高通量测序能够较为全面和准确的反映土壤微生物群落结构,而DGGE仅能够反映有限的优势微生物类群,在很大程度上极可能低估土壤微生物的物种组成并高估其丰度。
基金Supported by the Special Program of Scientific and Technological Promotion of Fisheries in Guangdong(A201101I01,A201208E01)the Guangdong Scientific and Technological Planning Program(2012B020415006)~~
文摘To know the bacterial communities structure in Babylonia areolata culture systems and to research and optimize the management pattem of Babylonia areola-ta culture systems of the pond mulched plastic film and sand in bottom, the bacte- rial communities in Babylonia areolata culture systems of the sub-tidal zone and the pond mulched plastic film and sand in bottom were analyzed at molecular level by adopting the denaturing gradient gel electrophoresis （DGGE）. The results indicated that the dominant bacterial communities in Babylonia areolata culture systems of the sub-tidal zone and the pond mulched plastic film and sand in bottom, which were built on the basis of the seawater in East-island of Zhanjiang, included Proteobac- teda Chloroflexi, Cyanobacteria and Actinobacteria. The dominant bacterial groups in the above pond culture system were Garnmaproteobacteria, Alphaproteobacteria, Deltaprotecbacteda, Epsilonproteobacteda, Anaerolineae, Cyanobacteria and Acti- nobacteda. The dominant bacterial communities in the subtidal zone culture system were Gammaprotecbacteda, Alphaproteobacteria, Deltaproteobacteria, Anaerolineae and Cyanobacteda, and there were less Epsilonproteobacteria and Actinobacteria in the culture system. The higher diversity was detected in the above two culture sys- tems. The results of unweighted pair group method with arithmetic average （UPG- MA） showed that the bacterial communities of the sediment samples S1 and S2 in the above two culture systems were a cluster, the similarity of bacterial communities was 54.5%. The bacterial communities of seawater samples S3 and S4 in the above culture systems were in clusters, and the similarity of the bacterial communi- ties was 84.0%. The results showed that the microorganism ecological level in the Babylonia areolata culture systems of the pond mulched plastic film and sand in bottom could be similar to the sub-tidal zone culture systems through changing the pond seawater and monitoring the microbial population.
