Differences In Bacterial Community Structure Research Articles

Early Changes in Soil Metabolic Diversity and Bacterial Community Structure in Sugarcane under Two Harvest Management Systems

Preharvest burning is widely used in Brazil for sugarcane cropping. However, due to environmental restrictions, harvest without burning is becoming the predominant option. Consequently, changes in the microbial community are expected from crop residue accumulation on the soil surface, as well as alterations in soil metabolic diversity as of the first harvest. Because biological properties respond quickly and can be used to monitor environmental changes, we evaluated soil metabolic diversity and bacterial community structure after the first harvest under sugarcane management without burning compared to management with preharvest burning. Soil samples were collected under three sugarcane varieties (SP813250, SP801842 and RB72454) and two harvest management systems (without and with preharvest burning). Microbial biomass C (MBC), carbon (C) substrate utilization profiles, bacterial community structure (based on profiles of 16S rRNA gene amplicons), and soil chemical properties were determined. MBC was not different among the treatments. C-substrate utilization and metabolic diversity were lower in soil without burning, except for the evenness index of C-substrate utilization. Soil samples under the variety SP801842 showed the greatest changes in substrate utilization and metabolic diversity, but showed no differences in bacterial community structure, regardless of the harvest management system. In conclusion, combined analysis of soil chemical and microbiological data can detect early changes in microbial metabolic capacity and diversity, with lower values in management without burning. However, after the first harvest, there were no changes in the soil bacterial community structure detected by PCR-DGGE under the sugarcane variety SP801842. Therefore, the metabolic profile is a more sensitive indicator of early changes in the soil microbial community caused by the harvest management system.

Biofumigation using a wild Brassica oleracea accession with high glucosinolate content affects beneficial soil invertebrates

Aims This study explores the biofumigation effects of glucosinolate (GSL) containing Brassica oleracea plant material on beneficial, non-target soil organisms, and aims to relate those effects to differences in GSL profiles. Methods Leaf material of purple sprouting broccoli ‘Santee’, Savoy cabbage ‘Wintessa’, and the wild B. oleracea accession Winspit was analysed for GSL production and used for biofumigation experiments on the beneficial soil invertebrates, Folsomia candida (springtail) and Eisenia andrei (earthworm) and the soil bacterial community. Results When mixed into soil, the Winspit plant material exerted the highest toxic effects on beneficial soil invertebrates by reducing survival and reproduction. Total GSL levels varied substantially between genotypes, in particular the aliphatic GSL (AGSL) sinigrin and gluconapin being highly abundant or exclusively present in Winspit. Differences between the genotypes regarding biofumigation effects on the soil microbial communitywereonlyobservedonatemporalbasiswith the largest difference in bacterial community structure after 1 week. Conclusions Thehightotal GSLcontent inbiofumigated soil could explain the toxicity of Winspit for soil invertebrates. These effects are likely to be the results of high AGSL levels in Winspit. The use of wild B. oleracea crops, such as Winspit, for biofumigation practices would need a proper assessment of the overall impact on soil biota before being applied on a wide scale.

Variations of Bacterial Community Structure and Composition in Mangrove Sediment at Different Depths in Southeastern Brazil

Tropical mangroves are considered one of the most productive ecosystems of the world, being characterized as nurseries and food sources for fish and other animals. Microorganisms play important roles in these environments, and the study of bacterial communities is of paramount importance for a better comprehension of mangrove dynamics. This study focused on the structure and composition of bacterial communities in mangrove sediments at different depths and points, located in Southeastern Brazil. Terminal Restriction Fragment Length Polymorphism (T-RFLP) was used to determine the community structure, and 16S rRNA gene pyrosequencing was used to characterize the community composition. Redundancy analysis of T-RFLP patterns revealed differences in bacterial community structure according to soil attributes and depth. The parameters K and depth presented significant correlation with general community structure. Most sequences were classified into the phylum Proteobacteria (88%), which presented differences according to the depth, where the classes Betaproteobacteria (21%) and Deltaproteobacteria (16%) were abundant at 10 cm and Epsilonproteobacteria (35%) was abundant at 40 cm depth. Clear differences were observed in community composition as shown by the differential distribution of the phyla Firmicutes (1.13% and 3.8%, for 10 cm and 40 cm respectively), Chloroflexi (2.8% and 0.75%), and Acidobacteria (2.75% and 0.57%) according to the depth. Bacterial diversity measurements indicated higher diversity in shallow samples. Taken together, our findings indicate that mangrove holds a diverse bacterial community, which is shaped by the variations found in the ecosystem, such as sediment properties and depth.

Parent material and vegetation influence bacterial community structure and nitrogen functional genes along deep tropical soil profiles at the Luquillo Critical Zone Observatory

Microbial communities mediate every step of the soil nitrogen cycle, yet the structure and associated nitrogen cycle functions of soil microbial communities remain poorly studied in tropical forests. Moreover, tropical forest soils are often many meters deep, but most studies of microbial nitrogen cycling have focused exclusively on surface soils. The objective of our study was to evaluate changes in bacterial community structure and nitrogen functional genes with depth in soils developed on two contrasting geological parent materials and two forest types that occur at different elevations at the Luquillo Critical Zone Observatory in northeast Puerto Rico. We excavated three soil pits to 140 cm at four different sites representing the four soil × forest combinations (n = 12), and collected samples at ten-centimeter increments from the surface to 140 cm. We used bacterial 16S rRNA gene-DGGE (denaturant gradient gel electrophoresis) to fingerprint microbial community structures, and quantitative PCR to measure the abundance of five functional genes involved in various soil nitrogen transformations: nifH (nitrogen fixation), chiA (organic nitrogen decomposition), amoA (ammonia oxidation), nirS (nitrite reduction) and nosZ (nitrous oxide reduction). Multivariate analyses of DGGE fingerprinting patterns revealed differences in bacterial community structure across the four soil × forest types that were strongly correlated with soil pH (r = 0.69, P < 0.01) and nutrient stoichiometry (r2 ≥ 0.36, P < 0.05). Across all soil and forest types, nitrogen functional genes declined significantly with soil depth (P < 0.001). Denitrification genes (nirS and nosZ) accounted for the largest proportion of measured nitrogen functional genes. Measured nitrogen functional genes were positively correlated with soil carbon, nitrogen and phosphorus concentrations (P < 0.001) and all genes except amoA were significantly more abundant in the Inceptisol soil type compared with the Oxisol soil type (P < 0.03). Greater abundances and a stronger vertical zonation of nitrogen functional genes in Inceptisols suggest more dynamic nitrogen transformation processes in this soil type. As the first study to examine bacterial nitrogen functional gene abundances below the surface 20 cm in tropical forest soils, our work provides insight into how pedogenically-driven vertical gradients control the nitrogen-cycling capacity of soil microbial communities. While previous studies have shown evidence for redox-driven hotspots in tropical nitrogen cycling on a watershed scale, our study corroborates this finding on a molecular scale.

Bacterial community structure in maize stubble-amended soils with different moisture levels estimated by bar-coded pyrosequencing

It is of ecological significance to investigate microbial communities in response to straw amendment and moisture in arable soils. However, in Chinese fluvo-aquic soils, these responses are still poorly understood. We designed an incubation experiment involving two soils with and without the addition of maize stubble at two moisture levels, and bacterial community structure at days 20, 80, and 200 after the start of incubation was assessed via bar-coded pyrosequencing of the 16S rDNA amplicons. In the presence of stubble with identical moisture level, we observed higher bacterial diversity and richness in long-term organic manure-fertilized soil compared with the unfertilized soil at days 20 and 80, which we attributed to the different quality and quantity of organic matter between the two soils. However, there was no significant difference in bacterial diversity and richness between the two soils at day 200, indicating that long-term straw amendment probably lessens the difference in bacterial community structure between the two soils. In the amended soils bacterial diversity, richness, and community composition at 25% of the water-holding capacity distinctly differed from those at 55% of the water-holding capacity, indicating that moisture strongly affects bacterial distribution in the amended soils. As stubble-C availability declined over time, the dominance of copiotrophic population weakened, and oligotrophic population was moderately abundant. Finally, our study suggests that dissolved organic carbon, which drives redistribution in copiotrophic and oligotrophic categories in response to the varying water and stubble-C availability, is a determinant of bacterial community composition in the amended soils.

Faecal Microbiome of the Thoroughbred Racehorse and Its Response to Dietary Amylase Supplementation

IntroductionThe horse has evolved to survive on a low‐energy, high‐fibre diet. The addition of starch, in the form of cereals, to the diet of racehorses to satisfy the high energy demands of extreme exercise has been identified as a risk factor for intestinal dysfunction. In this study we use 454 pyrosequencing of 16S rRNA genes to characterize the gut microbiome of 8 Thoroughbred (Tb) racehorses and study the response to dietary supplementation.MethodsFaecal samples were collected from 8 Tb racehorses in training. A second sample was collected from all horses six weeks after commencement of twice daily dietary supplementation with an amylase‐rich malt extract, designed to enhance pre‐caecal digestion. Amplicons for the V1‐V3 region of the 16S rDNA gene were multiplexed and sequenced on the 454 resulting in ∼25,000 reads per sample. Differences in bacterial community structure were detected by linear discriminant analysis.ResultsCommunities were composed of an equal balance between Bacteroidetes and Firmicutes with a ∼5% contribution from other bacterial phyla. The number of observed operational taxonomic units sharing ≥97% nucleotide sequence in our racehorse population was 6000–8000. Horses showed no significant change in the number of OTUs observed after diet supplementation, but significant changes in the relative abundance of both Bacteroidetes and Firmicutes families were observed.ConclusionsWe demonstrated a highly diverse and complex faecal microbial community in Tb racehorses in the UK. Inter‐horse variability is low amongst horses in the same training yard. We identified significant shifts in community profile following dietary supplementation and speculate that these may enhance intestinal health.Ethical Animal ResearchThis study was conducted under the University of Liverpool research ethics approval: RETH000363. The informed consent of the trainer was obtained and all samples were obtained non‐invasively. Sources of funding: private donation. Competing interests: none.

Biochar does not affect soil N-transformations or microbial community structure under ruminant urine patches but does alter relative proportions of nitrogen cycling bacteria

Nitrogen (N) cycling, especially denitrification, can be significantly altered when biochar is used as a soil conditioner. These alterations in N-cycling have been attributed to a combination of physicochemical change, alterations in microbial community ecology and pervading climatic conditions. This study investigated seasonal bacterial community change over two years in combination with a short-term winter study of N-transformations under bovine urine patches. A silt-loam pastoral soil in Canterbury, New Zealand was amended with either 0, 15 or 30tha−1 of Pinus radiata biochar (pyrolysed at ∼450°C) and bovine urine was added to patches within the 0 and 30tha−1 biochar amended plots (designated as 0U and 30U treatments, where U indicates ‘urine’).No discernible differences in bacterial community structure were observed during the two year study or the short term N-transformation study when comparing non-amended and biochar-amended soil. Differences in bacterial community structure were only evident when comparing seasons, with data pertaining to each season from successive years clustering together. During the short-term N-transformation study, bacterial communities formed 3 distinct clusters corresponding to elevated levels of urine derived NH4+-N (days 0–10), increases in NO3−-N and N2O (days 10–22) and a decline in NO3−-N and N2O (day 20 onward). Biochar amendment did increase the relative abundance of up to 50% of individual operational taxonomic units (OTUs or ‘species’), including key nitrite oxidisers and nitrate reducers. Biochar amendment did not affect the concentrations of inorganic-N compounds.The nirS (nitrite reductase) gene became elevated in the 30U treatment relative to the 0U treatment ∼10 days after the initial urine application. The nosZ (nitrous oxide reductase) gene became elevated in the 30U plots during the latter part of the experiment.Conclusions:•Biochar did not have a significant impact on the microbial community structure in pastoral soil over the course of two years.•The relative proportion of nitrifiers and denitrifiers increased in biochar amended soils subjected to large influxes of urine derived N.•Differences in N-transformation dynamics in the presence of biochar during the winter months were not statistically significant.

Minor differences in sand physicochemistry lead to major differences in bacterial community structure and function after exposure to synthetic acid mine drainage

The formation of environmentally toxic acidic waste from mining activities is a world-wide problem. Neutralization of this waste can be accomplished by physicochemical and/or biological means. In this short-term study, synthetic acid mine drainage was added to sand-filled mesocosms containing silica-dominated (quartz) sand. Glucose was added as a carbon source for microbial iron and/or sulphate reduction. Replicates contained two separate batches of sand obtained from the same quarry site. The investigations used to assess and compare the chemical and biological functioning of the replicates included system hydraulic conductivity measurements, sand chemistry, effluent chemistry and bacterial community fingerprinting. Minor differences in composition of the sand, including the levels of available nutrients and micronutrients, resulted in major differences in measured parameters. Significant differences in effluent chemistry were found in systems containing different batches of sand. It was demonstrated that the characteristics of the sand and the presence of acid mine drainage (AMD) impacted the bacterial community structure and function. The importance of the physical substrate on the selection of functional microbial communities in systems remediating AMD should not be under-estimated. The physical substrate should be carefully selected and it may be prudent to include small-scale comparative studies in each particular setting prior to full-scale implementation.

Coupled cryoconite ecosystem structure-function relationships are revealed by comparing bacterial communities in alpine and Arctic glaciers

Cryoconite holes are known as foci of microbial diversity and activity on polar glacier surfaces, but are virtually unexplored microbial habitats in alpine regions. In addition, whether cryoconite community structure reflects ecosystem functionality is poorly understood. Terminal restriction fragment length polymorphism and Fourier transform infrared metabolite fingerprinting of cryoconite from glaciers in Austria, Greenland and Svalbard demonstrated cryoconite bacterial communities are closely correlated with cognate metabolite fingerprints. The influence of bacterial-associated fatty acids and polysaccharides was inferred, underlining the importance of bacterial community structure in the properties of cryoconite. Thus, combined application of T-RFLP and FT-IR metabolite fingerprinting promises high throughput, and hence, rapid assessment of community structure-function relationships. Pyrosequencing revealed Proteobacteria were particularly abundant, with Cyanobacteria likely acting as ecosystem engineers in both alpine and Arctic cryoconite communities. However, despite these generalities, significant differences in bacterial community structures, compositions and metabolomes are found between alpine and Arctic cryoconite habitats, reflecting the impact of local and regional conditions on the challenges of thriving in glacial ecosystems.

A novel function of controlled-release nitrogen fertilizers.

A novel function of controlled-release nitrogen fertilizers.

Rhizosphere microbiome assemblage is affected by plant development.

There is a concerted understanding of the ability of root exudates to influence the structure of rhizosphere microbial communities. However, our knowledge of the connection between plant development, root exudation and microbiome assemblage is limited. Here, we analyzed the structure of the rhizospheric bacterial community associated with Arabidopsis at four time points corresponding to distinct stages of plant development: seedling, vegetative, bolting and flowering. Overall, there were no significant differences in bacterial community structure, but we observed that the microbial community at the seedling stage was distinct from the other developmental time points. At a closer level, phylum such as Acidobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria and specific genera within those phyla followed distinct patterns associated with plant development and root exudation. These results suggested that the plant can select a subset of microbes at different stages of development, presumably for specific functions. Accordingly, metatranscriptomics analysis of the rhizosphere microbiome revealed that 81 unique transcripts were significantly (P<0.05) expressed at different stages of plant development. For instance, genes involved in streptomycin synthesis were significantly induced at bolting and flowering stages, presumably for disease suppression. We surmise that plants secrete blends of compounds and specific phytochemicals in the root exudates that are differentially produced at distinct stages of development to help orchestrate rhizosphere microbiome assemblage.

Bacterial community structure and microbial activity in different soils amended with biogas residues and cattle slurry

Anaerobic digestion of organic materials generates residues of differing chemical composition compared to undigested animal manures, which may affect the soil microbial ecosystem differently when used as fertilizers. This study investigated the effects of two biogas residues (BR-A and BR-B) and cattle slurry (CS) applied at rates corresponding to 70kgNH4+-Nha−1 on bacterial community structure and microbial activity in three soils of different texture (a sandy, a clay and an organic clay soil). 16S rRNA genes were targeted in PCR reactions and bacterial community profiles visualized using terminal restriction fragment length polymorphism. General microbial activity was measured as basal respiration (B-resp), substrate-induced respiration (SIR), specific growth rate (μSIR), metabolic quotient (qCO2) and nitrogen mineralization capacity (NMC). Non-metric multidimensional scaling analysis visualized shifts in bacterial community structure related to microbial functions. There were significant differences in bacterial community structure after 120 days of incubation (+20°C at 70% of WHC) between non-amended (control) and amended soils, especially in the sandy soil, where CS caused a more pronounced shift than biogas residues. Terminal-restriction fragment (TRF) 307, the predominant peak in CS-amended sandy soil, was identified as possibly Bacillus or Streptococcus. TRF 226, the dominant peak in organic soil amended with BR-B, was classified as Rhodopseudomonas. B-resp significantly increased and SIR decreased in all amendments to organic soil compared with the control, potentially indicating decreased efficiency of heterotrophic microorganisms to convert organic carbon into microbial biomass. This was also reflected in an elevated qCO2 in the organic soil. The μSIR level was higher in the sandy soil amended with BR-A than with BR-B or CS, indicating a shift toward species capable of rapidly utilizing glucose. NMC was significantly elevated in the clay and organic soils amended with BR-A and BR-B and in the sandy soil amended with BR-B and CS. Thus, biogas residues and cattle slurry had different effects on the bacterial community structure and microbial activity in the three soils. However, the effects of biogas residues on microbial activities were comparable in magnitude to those of cattle slurry and the bacterial community structure was less affected. Therefore, we do not see any reason not to recommend using biogas residues as fertilizers based on the results presented.

Structure and variability of a microbial community at a transect crossing a double gyre structure in the northeastern Adriatic Sea

The effect of environmental conditions on bacterial community structures, production and enzymatic activities was studied in north-eastern Adriatic in the late spring of 2009 in waters belonging to the two gyres, the cyclonic (CG) and the anticyclonic (AG) one, and in waters non-affected by presence of the two gyres. The AG and CG were formed in a same pool of warm, low salinity, nutrient rich waters characterized with increased autotrophic production and abundances. Differences in bacterial community structures and in intensities of cell-specific prokaryotic production and enzymatic activities indicated that CG and AG were isolated cells in which water resided for different time period. Bulk prokaryotic production and enzymatic activities were significantly lower in region outside the influence of the gyres. Bacterial communities of these waters, particularly in deeper layers, were likely introduced by high salinity oligotrophic waters from central Adriatic.

Bacterioplankton community structure in the Arctic waters as revealed by pyrosequencing of 16S rRNA genes

Fjords and open oceans are two typical marine ecosystems in the Arctic region, where glacial meltwater and sea ice meltwater have great effects on the bacterioplankton community structure during the summer season. This study aimed to determine the differences in bacterioplankton communities between these two ecosystems in the Arctic region. We conducted a detailed census of microbial communities in Kongsfjorden (Spitsbergen) and the Chukchi Borderland using high-throughput pyrosequencing of the 16S rRNA gene. Gammaproteobacteria and Bacteroidetes were the dominant members of the bacterioplankton community in Kongsfjorden. By contrast, the most abundant bacterial groups in the surface seawater samples from the Chukchi Borderland were Alphaproteobacteria and Actinobacteria. Differences in bacterial communities were found between the surface and subsurface waters in the investigation area of the Chukchi Borderland, and significant differences in bacterial community structure were also observed in the subsurface water between the shelf and deep basin areas. These results suggest the effect of hydrogeographic conditions on bacterial communities. Ubiquitous phylotypes found in all the investigated samples belonged to a few bacterial groups that dominate marine bacterioplankton communities. The sequence data suggested that changes in environmental conditions result in abundant rare phylotypes and reduced amounts of other phylotypes.

Biogeography and Host Fidelity of Bacterial Communities in Ircinia spp. from the Bahamas

Research on sponge microbial assemblages has revealed different trends in the geographic variability and specificity of bacterial symbionts. Here, we combined replicated terminal-restriction fragment length polymorphism (T-RFLP) and clone library analyses of 16S rRNA gene sequences to investigate the biogeographic and host-specific structure of bacterial communities in two congeneric and sympatric sponges: Ircinia strobilina, two color morphs of Ircinia felix and ambient seawater. Samples were collected from five islands of the Bahamas separated by 80 to 400 km. T-RFLP profiles revealed significant differences in bacterial community structure among sponge hosts and ambient bacterioplankton. Pairwise statistical comparisons of clone libraries confirmed the specificity of the bacterial assemblages to each host species and differentiated symbiont communities between color morphs of I. felix. Overall, differences in bacterial communities within each host species and morph were unrelated to location. Our results show a high degree of symbiont fidelity to host sponge across a spatial scale of up to 400 km, suggesting that host-specific rather than biogeographic factors play a primary role in structuring and maintaining sponge-bacteria relationships in Ircinia species from the Bahamas.

Assessment of the bacterial community diversity associated with the queen conchStrombus gigas(Linnaeus, 1758) from the Caribbean coast of Colombia using denaturing gradient gel electrophoresis and culturing

The biotic diversity of Strombus gigas has not been thoroughly studied despite the status of the queen conch as an important ecological resource. The bacteria associated with the conch influence their host in several ways, including through the metabolism of nutrients, protection against invasive bacteria and the regulation of the physical conditions. In this study, conventional microbiological methods and molecular tools such as denaturing gradient gel electrophoresis (DGGE) were used to assess the composition of the bacterial communities associated with the queen conch (S. gigas) in wild and captive habitats in Colombia. A genetic analysis of the bacterial communities revealed a high level of diversity based on the large number of bands detected using DGGE. In addition, differences in bacterial community structure were found between the conchs in captivity and the wild populations. The dominant phylogenetic affiliations of the bacteria, as determined using 16S rRNA gene sequencing, were grouped into four classes, namely, Betaproteobacteria (16%), Gammaproteobacteria (70%), Firmicutes (7%) and Actinobacteria (2%). These groups are related to host defence processes and the decomposition of organic matter. The 16S rDNA sequence analysis of the cultured bacteria and the resulting DGGE profiles are useful tools for characterizing the diversity of the bacteria associated with the analyzed conchs.

Use of bacterial communities to assess the ecological health of a recently restored stream

We assess the utility of bacterial community data for providing an indication of stream health in a recently ‘restored’ urban stream. A community DNA fingerprinting technique was used to characterise the bacterial community within Okeover Stream, and a lesser impacted, nearby stream. No significant differences in bacterial community structure were detected between streams. However, further investigation revealed highly elevated levels of Zn, Pb and Cu associated with microbial biofilms in Okeover Stream and an increased abundance of genes encoding for bacterial resistance to Co, Zn and Cd. Benthic invertebrates were also sampled, confirming that despite recent attempts at stream restoration, the ecological health of the Okeover Stream remains poor. While the analysis of macroinvertebrate communities appeared to provide a more informative measure of overall stream health, we show that the targeted analysis of bacterial functional genes can be used to identify possible causes of declining ecological health.

Biogeography of bacterial communities in hot springs: a focus on the actinobacteria

Actinobacteria are ubiquitous in soil, freshwater and marine ecosystems. Although various studies have focused on the microbial ecology of this phylum, data are scant on the ecology of actinobacteria endemic to hot springs. Here, we have investigated the molecular diversity of eubacteria, with specific focus on the actinobacteria in hot springs in Zambia, China, New Zealand and Kenya. Temperature and pH values at sampling sites ranged between 44.5 and 86.5°C and 5-10, respectively. Non-metric multidimensional scaling analysis of 16S rRNA gene T-RFLP patterns showed that samples could be separated by geographical location. Multivariate analysis showed that actinobacterial community composition was best predicted by changes in pH and temperature, whereas temperature alone was the most important variable explaining differences in bacterial community structure. Using 16S rRNA gene libraries, 28 major actinobacterial OTUs were found. Both molecular techniques indicated that many of the actinobacterial phylotypes were unique and exclusive to the respective sample. Collectively, these results support the view that both actinobacterial diversity and endemism are high in hot spring ecosystems.

Composition and stability of bacterial communities associated with granular activated carbon and anthracite filters in a pilot scale municipal drinking water treatment facility

Granular activated carbon (GAC) is an alternative filter substrate for municipal water treatment as it provides a high surface area suitable for microbial colonization. The resulting microbial growth promotes biodegradation of organic materials and other contaminants from influent waters. Here, the community structure of the bacteria associated with three GAC and two anthracite filters was examined over 12 months to monitor changes in community composition. Nearly complete 16S rRNA genes were polymerase chain reaction amplified for terminal restriction fragment length polymorphism (T-RFLP) analyses. The identity of commonly occurring peaks was determined through the construction of five representative 16S rRNA clone libraries. Based on sequence analysis, the bacterial communities associated with both anthracite and GAC filters appear to be composed of environmentally derived bacteria, with no known human pathogens. Analysis of similarity tests revealed that significant differences in bacterial community structure occurred over time, with filter substrate playing an important role in determining community composition. GAC filters exhibited the greatest degree of bacterial community variability over the sampling period, while anthracite filters showed a lower degree of variability and less change in community composition. Thus, GAC may be a suitable biologically active filter substrate for the treatment of municipal drinking water.

温水沤麻与酶法沤麻液细菌群落结构分析

为了研究温水沤麻与酶法沤麻液中细菌群落结构，采用DGGE技术(Denaturing gradient gel electrophoresis)对沤麻液的细菌菌群结构进行了分析。采用DGGE分析细菌多样性时，当凝胶浓度为8%，变性剂梯度范围为25%~65%，恒温60℃、150 V电压下电泳7 h左右时，DGGE分离的效果较好。PCR-DGGE指纹图谱显示，亚麻温水脱胶及酶法脱胶过程中条带数量不同。通过对温水沤麻与酶法沤麻样品不同时期沤麻液中16S rDNA V3片段PCR产物的DGGE条带进行分子克隆、序列测定和Blast分析及建立系统发育树。从序列结果中我们发现，γ-变形菌亚门中的假单胞菌为温水沤麻与酶法沤麻过程中的共同优势菌属。芽孢杆菌属的出现伴随着整个温水沤麻和酶法沤麻过程。此外，温水沤麻与酶法沤麻样品群落结构多样性也表现了一定的差异性。 In order to investigate the bacterial community diversity of warm water retting liquid and enzymatic retting liquid, both of the retting liquid samples were studied by using Denaturing Gradient Gel Electrophoresis (DGGE). During using DGGE method to analyze the bacterial diversity, DGGE bands were separated obviously by the gel concentration of 8%, range of 25% - 65% denaturant gradient, temperature of 60˚C and voltage of 150 V for electrophoresis time of about 7 h. Through analysis, the selected bands of DGGE profiles were cloned and sequenced. The obtained sequence results by Blast analysis were used to construct the phylogenetic tree. We found Pseudomonas of Gammaproteobacteria were the dominant bacteria both in warm water retting and enzymatic retting liquid samples. Bacillus of Firmicutes occurred along with the whole process of the two retting samples. However, in addition to share the dominant bacteria, the two samples also represented the differences in bacterial community structure.