共查询到20条相似文献,搜索用时 15 毫秒
1.
Hermanni Kaartokallio Jaana Tuomainen Harri Kuosa Jorma Kuparinen Pertti J. Martikainen Kristina Servomaa 《Polar Biology》2008,31(7):783-793
Coastal fast ice and underlying water of the northern Baltic Sea were sampled throughout the entire ice winter from January
to late March in 2002 to study the succession of bacterial biomass, secondary production and community structure. Temperature
gradient gel electrophoresis (TGGE) and sequencing of TGGE fragments were applied in the community structure analysis. Chlorophyll-a and composition of autotrophic and heterotrophic assemblages were also examined. Overall succession of ice organism assemblages
consisted of a low-productive stage, the main algal bloom, and a heterotrophic post-bloom situation, as typical for the study
area. The most important groups of organisms in ice in terms of biomass were dinoflagellates, plasticidic flagellates, rotifers
and ciliates. Ice bacteria showed a specific succession not directly dependent on the overall succession events of ice organisms.
Sequenced 16S rDNA fragments were mainly affiliated to α-, β-, and γ-proteobacterial phyla and Cytophaga–Flavobacterium–Bacteroides-group, and related to sequences from cold environments, also from the Baltic Sea. Temporal clustering of the TGGE fingerprints
was stronger than spatial, although lower ice and underlying water communities always clustered together, pointing to the
importance of ice maturity and ice–water interactions in shaping the bacterial communities. 相似文献
2.
The community structure of the bacteria associated with Nodularia spumigena (Mertens) cyanobacterial aggregates in the Baltic Sea was studied with temperature gradient gel electrophoresis (TGGE), using a 16S rRNA gene fragment as a target. Various developmental stages of the aggregates and free-floating cyanobacterial filaments were sampled to reveal possible changes in associated microbial community structure during development and senescence of the aggregates. The microbial community structures of all samples differed, and the communities of young and decaying aggregates were separated by cluster analysis of the TGGE fingerprint data. Sequencing of the TGGE fragments indicated the presence of bacteria from the α-, β-, and γ-proteobacterial groups, as well as members of Cytophaga–Flexibacter–Bacteroides lineages and gram-positive Actinobacteria spp. The majority of the Nodularia-associated sequences were not closely related to previously reported 16S rDNA sequences from the Baltic Sea or any other environment. The structure of the bacterial assemblage reflects the environmental changes associated with the succession and decay of the cyanobacterial aggregates. In addition, the sequence data suggest that the N. spumigena (Mertens) blooms in the Baltic Sea may host thus far uncharacterized bacterial species. 相似文献
3.
Sunscreen Products Increase Virus Production Through Prophage Induction in Marine Bacterioplankton 总被引:1,自引:0,他引:1
Classical pollutants (e.g., hydrocarbon, pesticides) have been recently recognized to induce lytic cycle in lysogenic bacteria,
but information on micro-pollutants is almost completely lacking. We investigated the effects of cosmetic sun products (sunscreen
and solar oil) on viral abundance and bacterial activity. We found that both sunscreen and solar oil acted as pollutants,
inducing viral development and controlling bacterial abundance and production, thus leading to an increase of the virus to
bacterium ratio. Short-term experiments revealed that sunscreen supplementation induced the lytic cycle in a large fraction
of total bacterial abundance (13–24% of bacteria, at low and high concentrations, respectively), whereas solar oil had a lower
impact (6–9%). A synchronized development of the phage–host system was observed only after sunscreen addition. The addition
of sunscreen, even at low concentrations, had a significant impact on all enzymatic activities (aminopeptidase, glucosidase,
and phosphatase), which increased significantly. However, when enzymatic activities were normalized per cell, a selective
enhancement was observed for certain enzymes (e.g., aminopeptidase) and inhibition for others (e.g., glucosidase). These results
indicate that sunscreen products can modify C, N, and P biogeochemical cycling in seawater and increase virus abundance through
prophage induction in marine bacterioplankton. 相似文献
4.
TGGE analysis of the diversity of ammonia-oxidizing and denitrifying bacteria in submerged filter biofilms for the treatment of urban wastewater 总被引:3,自引:0,他引:3
Gómez-Villalba B Calvo C Vilchez R González-López J Rodelas B 《Applied microbiology and biotechnology》2006,72(2):393-400
The spatial and temporal diversity of the bacterial community-forming biofilms in a pilot-scale submerged biofilter used for the treatment of urban wastewater was analyzed by a temperature-gradient gel electrophoresis (TGGE) approach. TGGE profiles based on partial sequence of the 16S rRNA gene showed that the community composition of the biofilms remained fairly stable along the column system and during the whole time of operation of the biofilter (more than 1 year). Community-profiling based on the amplification and separation of partial ammonia monooxygenase (amoA) and nitrous oxide reductase (nosZ) genes demonstrated that ammonia-oxidizing and denitrifying bacteria coexisted in both the anoxic and the aerated parts of the system. Several amoA and nosZ bands separated by TGGE were reamplified and sequenced, in order to further analyze the composition of these microbial communities in the biofilm. Phylogeny inferred from amoA/AmoA revealed the prevalence of Nitrosomonas species with five sequences affiliated to Nitrosomonas oligotropha, six sequences affiliated to Nitrosomonas europaea, and three sequences that showed only 75.7–76.1% identity of the DNA sequence with the closest described species (Nitrosomonas nitrosa). According to literature, this low identity value is indicative of previously undiscovered species. Eighteen new partial nosZ sequences were obtained which were mostly related to nosZ of gamma-proteobacteria (Pseudomonas) or clustered in the periphery of previously known denitrifying alpha-proteobacteria (Bradyrhizobium and Azospirillum). 相似文献
5.
Sergey Dobretsov Raeid M. M. Abed Sultan M. S. Al Maskari Jamal N. Al Sabahi Reginald Victor 《Journal of applied phycology》2011,23(6):983-993
Polar (water) and non-polar (ethyl acetate) extracts from the cyanobacterial layer (top 1–3 mm) of four hot spring microbial
mats in the Sultanate of Oman were tested for their antibacterial, antidiatom and quorum-sensing inhibitory activities under
natural conditions. The chemical composition of the active extracts was analysed using gas chromatography–mass spectrometry
(GC-MS). Cyanobacteria within these mats were identified by direct microscopy while the total bacterial community composition
was compared using automated ribosomal intergenic spacer analysis (ARISA). Only the extracts from Bowshar and Nakhl mats showed
antibacterial properties against Bacillus sp., Micrococcus luteus, Shigella sonnei, Salmonella enterica and Klebsiella pneumoniae. All tested extracts inhibited the growth of the benthic diatom Amphora coffeaeformis. Extracts from Bowshar, Rustaq and Nakhl inhibited quorum-sensing of the reporter strains Chromobacterium violaceum CV017 and Agrobacterium tumefaciens NTL4. The highest bioactivity was recorded for ethyl acetate extracts from Nakhl mats, which had the lowest number of operational
taxonomic units (OTUs). Using GC-MS, 74 chemical compounds were obtained, however with different distribution among the four
mat extracts (similarity < 43%). Various cyanobacteria, belonging mainly to Chroococcus, Phormidium, Leptolyngbya, Spirulina and Lyngbya were detected in the different mats, and each mat had its unique bacterial community, as confirmed by ARISA profiles. We
conclude that antimicrobial and quorum-sensing inhibitory compounds can be produced by hot spring mat microorganisms under
natural conditions and the differences in these compounds could be attributed to the differences in the mats’ bacterial composition
as well as the physical–chemical conditions of the springs. 相似文献
6.
Culture-independent PCR–denaturing gradient gel electrophoresis (DGGE) was employed to assess the composition of diazotroph
species from the sediments of three mangrove ecosystem sites in Sanya, Hainan Island, China. A strategy of removing humic
acids prior to DNA extraction was conducted, then total community DNA was extracted using the soil DNA kit successfully for
nifH PCR amplification, which simplified the current procedure and resulted in good DGGE profiles. The results revealed a novel
nitrogen-fixing bacterial profile and fundamental diazotrophic biodiversity in mangrove sediments, as reflected by the numerous
bands present DGGE patterns. Canonical correspondence analysis (CCA) revealed that the sediments organic carbon concentration
and available soil potassium accounted for a significant amount of the variability in the nitrogen-fixing bacterial community
composition. The predominant DGGE bands were sequenced, yielding 31 different nifH sequences, which were used in phylogenetic reconstructions. Most sequences were from Proteobacteria, e.g. α, γ, β, δ-subdivisions, and characterized by sequences of members of genera Azotobacter, Desulfuromonas, Sphingomonas, Geobacter, Pseudomonas, Bradyrhizobium and Derxia. These results significantly expand our knowledge of the nitrogen-fixing bacterial diversity of the mangrove environment. 相似文献
7.
Soil drying and rewetting represents a common physiological stress for the microbial communities residing in surface soils.
A drying–rewetting cycle may induce lysis in a significant proportion of the microbial biomass and, for a number of reasons,
may directly or indirectly influence microbial community composition. Few studies have explicitly examined the role of drying–rewetting
frequency in shaping soil microbial community structure. In this experiment, we manipulated soil water stress in the laboratory
by exposing two different soil types to 0, 1, 2, 4, 6, 9, or 15 drying–rewetting cycles over a 2-month period. The two soils
used for the experiment were both collected from the Sedgwick Ranch Natural Reserve in Santa Ynez, CA, one from an annual
grassland, the other from underneath an oak canopy. The average soil moisture content over the course of the incubation was
the same for all samples, compensating for the number of drying–rewetting cycles. At the end of the 2-month incubation we
extracted DNA from soil samples and characterized the soil bacterial communities using the terminal restriction fragment length
polymorphism (T-RFLP) method. We found that drying–rewetting regimes can influence bacterial community composition in oak
but not in grass soils. The two soils have inherently different bacterial communities; only the bacteria residing in the oak
soil, which are less frequently exposed to moisture stress in their natural environment, were significantly affected by drying–rewetting
cycles. The community indices of taxonomic diversity and richness were relatively insensitive to drying–rewetting frequency.
We hypothesize that drying–rewetting induced shifts in bacterial community composition may partly explain the changes in C
mineralization rates that are commonly observed following exposure to numerous drying–rewetting cycles. Microbial community
composition may influence soil processes, particularly in soils exposed to a significant level of environmental stress. 相似文献
8.
Bacterial diversity of the rhizosphere of maize (Zea mays) grown in tropical soil studied by temperature gradient gel electrophoresis 总被引:8,自引:0,他引:8
Gomes N. C. M. Heuer H. Schönfeld J. Costa R. Mendonça-Hagler L. Smalla K. 《Plant and Soil》2001,232(1-2):167-180
The bacterial diversity and population dynamics in the rhizosphere of two maize cultivars (Nitroflint and Nitrodent) grown in tropical soils was studied, by traditional cultivation techniques and 16S rRNA gene-based molecular analysis of DNA directly extracted from soil and rhizosphere samples. Rhizosphere and soil samples were taken at three different plant growth stages. Total aerobic bacterial counts were determined. Fingerprints of the most dominant bacterial population were generated by TGGE separation of 16S rRNA gene fragments amplified from total community DNA using eubacterial specific primers. To reduce the complexity of TGGE fingerprints or to analyse less abundant populations, primers specific for different phylogenetic groups have been used. A comparison of the cfu obtained for rhizosphere of both cultivars indicated significant differences only for rhizosphere and soil samples taken 40 days after sowing. However, a comparison of TGGE patterns indicated that the composition of the bacterial community analysed at different plant growth stages for both cultivars was similar. A comparison of -, -proteobacterial and actinomycete TGGE patterns of both cultivars confirmed this observation. The eubacterial TGGE profiles reflected strong seasonal population shifts in the bacterial rhizosphere community of both maize cultivars which could be also observed in the TGGE patterns of - and -proteobacteria and to a lesser extent for actinomycetes. The rhizosphere effect was much more pronounced for young roots compared to samples taken from mature maize plants. The rhizosphere fingerprints showed a reduced complexity for young plants with up to five dominating bands while for mature plants patterns similar to those of soil were observed. Sequencing of dominant clones indicated that the dominant population found at all plant growth stages can be assigned to Arthrobacter populations. 相似文献
9.
Bacterial Community Composition in Central European Running Waters Examined by Temperature Gradient Gel Electrophoresis and Sequence Analysis of 16S rRNA Genes 总被引:3,自引:1,他引:2
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The bacterial community composition in small streams and a river in central Germany was examined by temperature gradient gel electrophoresis (TGGE) with PCR products of 16S rRNA gene fragments and sequence analysis. Complex TGGE band patterns suggested high levels of diversity of bacterial species in all habitats of these environments. Cluster analyses demonstrated distinct differences among the communities in stream and spring water, sandy sediments, biofilms on stones, degrading leaves, and soil. The differences between stream water and sediment were more significant than those between sites within the same habitat along the stretch from the stream source to the mouth. TGGE data from an entire stream course suggest that, in the upper reach of the stream, a special suspended bacterial community is already established and changes only slightly downstream. The bacterial communities in water and sediment in an acidic headwater with a pH below 5 were highly similar to each other but deviated distinctly from the communities at the other sites. As ascertained by nucleotide sequence analysis, stream water communities were dominated by Betaproteobacteria (one-third of the total bacteria), whereas sediment communities were composed mainly of Betaproteobacteria and members of the Fibrobacteres/Acidobacteria group (each accounting for about 25% of bacteria). Sequences obtained from bacteria from water samples indicated the presence of typical cosmopolitan freshwater organisms. TGGE bands shared between stream and soil samples, as well as sequences found in bacteria from stream samples that were related to those of soil bacteria, demonstrated the occurrence of some species in both stream and soil habitats. Changes in bacterial community composition were correlated with geographic distance along a stream, but in comparisons of different streams and rivers, community composition was correlated only with environmental conditions. 相似文献
10.
Spatial Heterogeneity of Bacterial Populations in Monomictic Lake Estanya (Huesca,Spain) 总被引:2,自引:0,他引:2
Bacterial population changes were investigated in the monomictic Lake Estanya by combining microscopic analysis and two molecular
methods involving the amplification of 16S rDNA genes using primers for the domain Bacteria and subsequent restriction fragment length polymorphism (PCR–RFLP) and denaturing gradient gel electrophoresis (PCR–DGGE).
Both approaches revealed the vertical distribution of predominant microbial morphotypes and phylotypes in both holomictic
and stratified periods, respectively, and showed that variations in structure and composition of bacterial populations are
occurring in this lake as a function of depth and time. Through principal component analysis (PCA), these shifts could be
related to different physicochemical parameters with temperature, oxygen concentration, and the incident light being of paramount
importance as structuring variables. Comparison of RFLP and DGGE profiles by scoring similarities using the Jaccard coefficient
and then building a multidimensional scaling map (MDS) showed equivalent results. Both techniques revealed that bacterial
populations, present in the whole water column in the holomictic period, showed a high similarity with those located in the
deeper part of the lake in the stratified period, evidencing that other factors, both biotic and abiotic, should also be considered
as a force driving change in the composition of the bacterial community. Furthermore, DGGE analysis showed that sequences
from prominent bands were affiliated to members of four major phyla of the domain Bacteria: Cyanobacteria, Bacteroidetes, Proteobacteria, and Actinobacteria, most of which corresponded to heterotrophic bacterial populations involved in carbon, sulfide, and nitrogen biogeochemical
cycles, which were indistinguishable under the light microscope. 相似文献
11.
J. Compte S. Brucet S. Gascón D. Boix J. Sala R. López-Flores X. D. Quintana 《Hydrobiologia》2009,635(1):45-56
In situ 24-h incubation experiments were performed to analyse the grazing effects of Daphnia magna on a planktonic microbial community. Three field grazing experiments under different nutrient concentrations were carried
out on treated effluents of a wastewater treatment plant. The grazing effects of three different D. magna size classes (small (0.6–1.6 mm), medium (1.7–2.5 mm) and large individuals (2.6–3.7 mm)) were compared. The different sizes
classes had similar effects on the plankton community. However, our results showed big differences in effects among experiments.
Our findings suggest that in spite of D. magna’s non-selective feeding behaviour and the fact that different developmental stages (i.e. its size) had similar effects on the
microbial planktonic community, these effects can differ according to the initial structure and composition of the community
and the resulting cascading trophic interactions. Moreover, D. magna effects can be direct through grazing (as is the case with ciliates), or indirect through trophic cascade interactions (as
is the case with bacteria). 相似文献
12.
Bacterivorous protists are known to induce changes in bacterial community composition (BCC). We hypothesized that changes
in BCC could be related quantitatively to a measure of grazing: the ratio of bacterial mortality to growth rate. To test this
hypothesis, we analyzed time-course changes in BCC, protistan grazing rate, and bacterial production from 3 in situ studies conducted in a freshwater reservoir and three laboratory studies. In the field experiments, samples were manipulated
to yield different levels of protistan bacterivory and incubated in dialysis bags. Laboratory investigations were continuous
cultivation studies in which different bacterivorous protists were added to bacterial communities. BCC was assessed using
4–6 different rRNA-targeted oligonucleotide probes for community analysis. Change in BCC (Δ BCC) was estimated as the sum
of changes in the proportions of the two phylogenetic groups that showed the largest shifts. Analysis of a set of 22 estimates
of shifts in the ratio of grazing to production rate over periods of 48–72 h and Δ BCC showed that Δ BCC was positively and
tightly correlated (r
2 = 0.784) with shifts in the ratio of grazing mortality to cell production. While the nature of a shift in BCC is unpredictable,
the magnitude of the change can be related to changes in the balance between bacterial production and protistan grazing.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
Kim JR Beecroft NJ Varcoe JR Dinsdale RM Guwy AJ Slade RC Thumser A Avignone-Rossa C Premier GC 《Applied microbiology and biotechnology》2011,90(3):1179-1191
The spatiotemporal development of a bacterial community in an exoelectrogenic biofilm was investigated in sucrose-fed longitudinal
tubular microbial fuel cell reactors, consisting of two serially connected modules. The proportional changes in the microbial
community composition were assessed by polymerase chain reaction–denaturing gradient gel electrophoresis (DGGE) and DNA sequencing
in order to relate them to the performance and stability of the bioelectrochemical system. The reproducibility of duplicated
reactors, evaluated by cluster analysis and Jaccard’s coefficient, shows 80–90% similarity in species composition. Biofilm
development through fed-batch start-up and subsequent stable continuous operation results in a population shift from γ-Proteobacteria- and Bacteroidetes- to Firmicutes-dominated communities, with other diverse species present at much lower relative proportions. DGGE patterns were analysed
by range-weighted richness (Rr) and Pareto–Lorenz evenness distribution curves to investigate the evolution of the bacterial community. The first modules
shifted from dominance by species closely related to Bacteroides graminisolvens, Raoultella ornithinolytica and Klebsiella sp. BM21 at the start of continuous-mode operation to a community dominated by Paludibacter propionicigenes-, Lactococcus sp.-, Pantoea agglomerans- and Klebsiella oxytoca-related species with stable power generation (6.0 W/m3) at day 97. Operational strategies that consider the dynamics of the population will provide useful parameters for evaluating
system performance in the practical application of microbial fuel cells. 相似文献
14.
Bacterial community shifts in a soil microcosm spiked with 3-chlorobenzoate or 2,5-dichlorobenzoate were monitored. The V6-V8 variable regions of soil bacterial 16S rRNA and rDNA were amplified and separated by temperature gradient gel electrophoresis (TGGE) profiling. Culturing in the presence of 2.5 mM chlorinated benzoates suppressed 10 to 100 fold the total aerobic bacterial community but had no effect on the diversity within the group of fluorescent pseudomonads. In contrast, the uncultured bacterial community showed a decrease in the number of bands in the TGGE profiles of the chlorobenzoate-spiked treatments. Accordingly, the Shannon's diversity and equitability indices of these treatments reflected a decreasing trend in time. The approach allowed a direct assessment of community shifts upon contamination of soil. 相似文献
15.
The responses of epilithic bacterial and algal communities to sewage-treatment-works (STW) effluent were studied in three
streams in North Yorkshire, England, using both conventional microbiological techniques and the techniques of molecular genomics.
Cod Beck, Thornton Beck and the River Wiske, were visited in May–June 2000 and January 2001 and the epilithic communities
on submerged stones were sampled to determine chlorophyll-a, leucine assimilation, bacterial abundance, identity and abundance of microalgae, and epilithon dry and organic weights.
Additionally, DNA from the epilithon of stones, collected in March–April and November 2000, was extracted, and samples were
amplified using universal primers appropriate, respectively, for bacteria [Muyzer et al., 1993. Applied and Environmental
Microbiology 59: 695–700] and microscopic phototrophs [Nübel et al., 1997. Applied and Environmental Microbiology 63: 3327–3332]
followed by DGGE (Denaturing Gradient Gel Electrophoresis). Differences in algal community composition and abundance were
greater between streams than between sites upstream and downstream of the STW outfalls. DGGE banding profiles of bacterial
communities revealed grouping according to stream, and not the formation of communities characteristic of downstream sites;
seasonal variation was also evident. Thus the discharge of STW effluent to the streams did not bring about the development
of communities that are characteristically associated with organic pollution. Changes in composition and structure of bacterial
and micro-algal epilithic communities were detected, but the relatively high quality effluents had only mild effects, not
altering the environments sufficiently to override the natural differences between the three streams. 相似文献
16.
The temporal stability and change of the dominant phylogenetic groups of the domain bacteria were studied in a model plant-based
industrial wastewater treatment system showing high levels of organic carbon removal supported by high levels of N2 fixation. Community profiles were obtained through terminal restriction fragment length polymorphism analysis and cloning
of 16S rRNA amplicons followed by sequencing. Bacterial community profiles showed that ten common terminal restriction fragments
made up approximately 50% of the measured bacterial community. As much as 42% of the measured bacterial community could be
monitored by using quantitative PCR and primers that targeted three dominant operational taxonomic units. Despite changes
in wastewater composition and dissolved oxygen levels, the bacterial community composition appeared stable and was dominated
by α-Proteobacteria and β-Proteobacteria, with a lesser amount of the highly diverse bacterial phylum Bacteroidetes. A short
period of considerable change in the bacterial community composition did not appear to affect treatment performance indicating
functional redundancy in this treatment system. 相似文献
17.
The major parcel of the degradation occurring along wastewater biotreatments is performed either by the native microbiota
or by added microbial inocula. The main aim of this study was to apply two fingerprinting methods, temperature gradient gel
electrophoresis (TGGE) and length heterogeneity-PCR (LH-PCR) analysis of 16S rRNA gene fragments, in order to assess the microbiota
structure and dynamics during mixed olive oil and winery wastewaters aerobic biotreatment performed in a jet-loop reactor
(JLR). Sequence homology analysis showed the presence of bacterial genera Gluconacetobacter, Klebsiella, Lactobacillus, Novosphingobium, Pseudomonas, Prevotella, Ralstonia, Sphingobium and Sphingomonas affiliated with five main phylogenetic groups: alpha-, beta- and gamma-Proteobacteria, Firmicutes and Bacteroidetes. LH-PCR
analysis distinguished eight predominant DNA fragments correlated with the samples showing highest performance (COD removal
rates of 67 up to 75%). Cluster analysis of both TGGE and LH-PCR fingerprinting profiles established five main clusters, with
similarity coefficients higher than 79% (TGGE) and 62% (LH-PCR), and related with hydraulic retention time, indicating that
this was the main factor responsible for the shifts in the microbiota structure. Canonical correspondence analysis revealed
that changes observed on temperature and O2 level were also responsible for shifts in microbiota composition. Community level metabolic profile analysis was used to
test metabolic activities in samples. Integrated data revealed that the microbiota structure corresponds to bacterial groups
with high degradative potential and good suitability for this type of effluents biotreatments. 相似文献
18.
Abstract
A greenhouse study with soil–plant microcosms was conducted in order to compare the effect of crop species, soil origin, and
a bacterial inoculant on the establishment of microbial communities colonizing plant roots. Two crop species, alfalfa (Medicago sativa) and rye (Secale cereale), were grown separately in two soils collected from agricultural fields at different locations and with differing histories
of leguminous crop rotation. A subset of microcosms was inoculated at 106 cfu g-1 soil with the luciferase marker gene-tagged Sinorhizobium meliloti strain L33, a symbiotic partner of M. sativa. Microbial consortia were collected from the rhizospheres of alfalfa after 10 weeks of incubation and from rye after 11 weeks.
S. meliloti L33 populations were one to two orders of magnitude higher in the rhizospheres of alfalfa than of rye. In soil with previous
alfalfa cultivation, 80% of the alfalfa nodules were colonized by indigenous bacteria, while in the other soil alfalfa was
colonized almost exclusively (>90%) with S. meliloti L33. Three community-level targeting approaches were used to characterize the variation of the extracted microbial rhizosphere
consortia: (1) Community level physiological profiles (CLPP), (2) fatty acid methyl ester analysis (FAME), and (3) diversity
of PCR amplified 16S rRNA target sequences from directly extracted ribosomes, determined by temperature gradient gel electrophoresis
(TGGE). All approaches identified the crop species as the major determinant of microbial community characteristics. Consistently,
the influence of soil was of minor importance, while a modification of the alfalfa-associated microbial community structure
after inoculation with S. meliloti L33 was only consistently observed by using TGGE.
Received: 20 October 1999; Accepted: 15 January 2000; Online Publication: 18 July 2000 相似文献
19.
Bacterial community along a historic lake sediment core of Ardley Island, west Antarctica 总被引:6,自引:0,他引:6
The bacterial community in a historic lake sediment core of Ardley Island, Antarctica, spanning approximately 1,600 years, was investigated by molecular approaches targeting the 16S rRNA gene fragments. The cell number in each 1 cm layer of the sediment core was deduced through semi-quantification of the 16S rRNA gene copies by quantitative competitive PCR (QC-PCR). It was found that the total bacterial numbers remained relatively stable along the entire 59 cm sediment core. Denaturing Gradient Gel Electrophoresis (DGGE) analysis and sequencing of PCR-amplified 16S rRNA gene fragments were performed to analyze the bacterial diversity over the entire column. Principle coordinates analysis suggested that the bacterial communities along the sediment core could be separated into three groups. There were obvious bacterial community shift among groups of 1–20 cm, 21–46 cm and 46–59 cm. Diversity indices indicated that the bacterial community in the 21–46 cm depth showed the highest species diversity and uniformity. The main bacterial groups in the sediments fell into 4 major lineages of the gram-negative bacteria: the α, γ and δ subdivision of Proteobacteria, the Cytophaga-Flavobacteria-Bacteroides, and some unknown sequences. The gram-positive bacteria Gemmatimonadetes, Firmicutes and Actinobacteria were also detected. The results demonstrated the presence of highly diverse bacterial community population in the Antarctic lake sediment core. And the possible influence of climate and penguin population change on the bacterial community shift along the sediment core was discussed.Shengkang Li and Xiang Xiao contributed equally to this paper 相似文献
20.
Four experiments were conducted to assess the effect of foliar applications of various nutrient solutions on the phylloplane
yeast community of tall fescue (Festuca arundinacea Schreb.). In the first three experiments, increasing concentrations of sucrose (2–16%), yeast extract (0.5–2.5%), and sucrose
plus yeast extract (2.5–18.5% total) were applied and the yeast colony forming units (cfu) enumerated 14 h later by dilution
plating. Significant positive linear relationships were observed between the number of yeast cfu and applications of both
yeast extract and sucrose plus yeast extract. Foliar applications of sucrose alone had no significant effect on yeast community
abundance, indicating that phylloplane yeasts of turfgrass are not limited by the amount or availability of carbohydrates.
In the fourth experiment, five different solutions were applied to tall fescue to investigate the response of the yeast community
to organic and inorganic nitrogen sources. Tryptone or yeast extract, both with considerable amino acid composition, significantly
increased the yeast population, while yeast nitrogen base (with or without amino acids) and ammonium sulfate had no affect
on yeast abundance. These results suggest that organic nitrogen stimulate yeast community growth and development on the phylloplane
of tall fescue, while carbohydrates, inorganic nitrogen, and non-nitrogenous nutrients have little positive effect. 相似文献