Changes in microbial community composition in the leaf litter of successional communities after volcanic eruptions of Mount Usu, northern Japan

Changes in the fungal and bacterial biomass and community structure in litter after the volcanic eruptions of Mount Usu, northern Japan were investigated using a chronosequence approach, which is widely used for analyzing vegetation succession. The vegetation changed from bare ground （10 years after the eruptions） with little plant cover and poor soil to monotonic grassland dominated by Polygonum sachalinense with undeveloped soil （33 years） and then to deciduous broad-leaved forest dominated by Populus maximowiczii with diverse species composition and well-developed soil （100 years）. At three chronosequential sites, we evaluated the compositions of phospholipid fatty acids （PLFAs）, carbon （C） and nitrogen （N） contents and the isotope ratios of C （δ13C） and N （δ15N） in the litter of two dominant species, Polygonum sachalinense and Populus maximowiezii. The C/N ratio, δ13C and δ15N in the litter of these two species were higher in the forest than that in the bare ground and grassland. The PLFAs gradually increased from the bare ground to the forest, showing that microbial biomass increased with the development of the soil and/or vegetation. The fungi-to-bacteria ratio of PLFA was constant at 5.3 ± 1.4 in all three sites, suggesting that fungi were predominant. A canonical correspondence analysis suggested that the PLFA comoosition was related to the successional ages and the developing soil properties （P 〈 0.05, ANOSIM）. The chrono- sequential analysis effectively detected the successional changes in both microbial and plant communities.

Succession of aquatic microbial communities as a result of the water quality variations in continuous water

The changes of structural and functional parameters of aquatic microbial communities in continuous water on campus of Tsinghua University, China are investigated by polyurethane foam unit(PFU) method. The measured compositions of the communities include alga, protozoa, and some metazoa(such as rotifers). The measured indicators of water quality include water temperature, pH value, dissolved oxygen(DO), potassium permanganate index(COD Mn ), total nitrogen(TN), total phosphorus(TP) and chlorophyll-a(Chla). The trophic level, expressed by the trophic level indices(TLIc), is assessed with analytic hierarchy process and principal component analysis(AHP-PCA) method. The changing trends of the structural and functional parameters of aquatic microbial communities, such as Margalef index of diversity(D), Shannon-weaver index of diversity (H), Heterotropy index(HI), number of species when the colonization gets equilibrium(S eq ), colonizing speed constant(G) and time spent when 90 percent of S eq colonized in PFU(T 90% ), are also analyzed. The experimental results showed the succession of aquatic microbial communities along the water flow is consistent with the water quality changes, so the parameters of microbial community can reflect the changes of water quality from the ecological view.

Spatio-temporal succession of iron and manganese microbial community in biological filter layer

This paper studied the structure and dynamic change of microbial communities in bio-reactor for treating ground water which contained high concentration of iron and manganese.In this study,polymerase chain reaction(PCR) denaturing gradient gel electrophoresis(DGGE) was used to evaluate the bacterial diversity.Different samples in spatio-temporal of bacterial community suceession in sands were analyzed,and the removal of iron and manganese were discussed.The results showed that a significant change in the community structure was observed during running time and the bio-reactor which designed by ourselves:the removal rate of iron and manganese could achieve 88.93%.The mass of microrganisms was decreasing,and the type of micro-organisms tended to stable with the increase of operating time.Besides,the change of mass and types of micro-organisms in sands was related to temperature.Along the depth of filter layer,the mass and types of micro-organisms were gradually decreasing.Further,pseudomonas were found to be the main microbiology by recycling the band sequencing and phylogenetic analysis.And with time increasing the mass and kind of bacteria were growing from less to more,finally to be stable.

Research progress in enhanced bioleaching of copper sulfides under the intervention of microbial communities

Compared with the traditional pyrometallurgical process, copper bioleaching has distinctive advantages of high efficiency and lower cost, enabling efficiently extracts of valuable metal resources from copper sulfides. Moreover, during long-term industrial applications of bioleaching, many regulatory enhancements and technological methods are used to accelerate the interfacial reactions. With advances in microbial genetic and sequencing technologies, bacterial communities and their mechanisms in bioleaching systems have been revealed gradually. The bacterial proliferation and dissolution of sulfide ores by a bacterial community depends on the pH, temperature, oxygen, reaction product regulation, additives, and passivation substances, among other factors. The internal relationship among the influencing factors and the succession of microorganism diversity are discussed and reviewed in this paper. This paper is intended to provide a good reference for studies related to enhanced bioleaching.

Variations of bacterial and fungal communities along a primary successional chronosequence in the Hailuogou glacier retreat area(Gongga Mountain, SW China)

New terrestrial habitats have emerged and a primary succession has developed in the retreat area （29°34＇N, 102°oo＇E, 2951-2886 m） after the retreat of the Hailuogou glacier. To investigate soil microbial changes along the primary successional chronosequence, mixed soil samples were collected at six sites at different ages （2 young sites, 2 mid-aged sites, and 2 old sites）. The RNA was extracted and amplified. Bacterial 16S rRNA and fungal 18S rRNA were analyzed using high-throughput 454 pyrosequencing analysis. Overall, pyrosequeneing showed that Proteobacteria, Acidobacteria, Baeteroidetes and Actinobacteria were the main bacterial phyla, and the fungal communities were strongly dominated by the phyla Ascomyeota and Basidiomyeota in the retreat area. The Shannon diversity index （Hshannon） of bacteria was 6.5 - 7.9, and that of fungi was 2.2 - 4.1 in these sites. For the bacterial communities, diversity and evenness values were highest on the mid-age sites and were relatively low on the young trend was observed for the and old sites. A similar fungal communities. In contrast, soil properties showed significant linear distributional trends （increase or decrease） with the age of the site. Combining the linear change patterns of soil properties, the highest values of bacterial and fungal evenness and diversity in the mid-aged sites indicated that there was less environmental stress and more niches for microbial communities in the middle successional stage compare with other stages. In addition, our analysis showed that microbial communities were the main drivers that build a soil organic matter pool to expedite pedogenesis for ecosystem succession. This primary succession in the Hailuogou glacier retreat area is developing rapidly compared with that in other glacier retreats.

Characterization of microbial communities in sediments of the South Yellow Sea

Illumina sequencing and quantitative PCR(qPCR)based on the 16 S ribosomal RNA(rRNA)gene were conducted to characterize the vertical distribution of bacterial and archaeal communities in the sediments of two sites from the South Yellow Sea.Both bacterial and archaeal communities showed a clear stratified distribution with sediment depth.The microbial communities in the upper layers were distinct from those in the deeper layers;the relative abundances of sequences of Thaumarchaeota,Gammaproteobacteria,and Actinobacteria were higher in the upper than in the deeper sediments,whereas the sequences of Bathyarchaeia,Lokiarchaeota,Euryarchaeota,Chloroflexi,and Deltaproteobacteria were relatively more abundant in the deeper sediments.Sediment depth and total organic carbon(TOC)can significantly influence both the bacterial and archaeal communities.Furthermore,bacterial and archaeal groups potentially involved in nitrogen,sulfur,and methane metabolism were detected in both sites.In our study,both ammonia-oxidizing bacteria(Nitrospira)and ammonia-oxidizing archaea(Candidatus Nitrosopumilus)were responsible for ammonia oxidization.Additionally,sulfur-reducing bacteria SEEP-SRB1 forming consortia with anaerobic methane-oxidizing archaea ANME-2 a-2 b were capable of anaerobic methane oxidation(AOM)in the 3400-02 sediment samples.

Response of microbial biomass and bacterial community composition to fertilization in a salt marsh in China

The effects of nitrogen （N） addition on microbial biomass, bacterial abundance, and community composition in sediment colonized by Suaeda heteroptera were examined by chloroform fumigation extraction method, real-time quantitative polymerase chain reaction, and denaturing gradient gel electrophoresis （DGGE） in a salt marsh located in Shuangtai Estuary, China. The sediment samples were collected from plots treated with different amounts of a single N fertilizer （urea supplied at 0.1, 0.2, 0.4 and 0.8 g/kg （nitrogen content in sediment） and different forms of N fertilizers （urea, （NH4）2SO4, and NH4NO3, each supplied at 0.2 g/kg （calculated by nitrogen）. The fertilizers were applied 1-4 times during the plant-growing season in May, luly, August, and September of 2013. Untreated plots were included as a control. The results showed that both the amount and form of N positively influenced microbial biomass carbon, microbial biomass nitrogen, and bacterial abundance. The DGGE profiles revealed that the bacterial community composition was also affected by the amount and form of N. Thus, our findings indicate that short-term N amendment increases microbial biomass and bacterial abundance, and alters the structure of bacterial community.

Characteristics of maize residue decomposition and succession in the bacterial community during decomposition in Northeast China

Microbes are decomposers of crop residues,and climatic factors and residue composition are known to influence microbial growth and community composition,which in turn regulate residue decomposition.However,the succession of the bacterial community during residue decomposition in Northeast China is not well understood.To clarify the property of bacterial community succession and the corresponding factors regulating this succession,bags containing maize residue were buried in soil in Northeast China in October,and then at different intervals over the next 2 years,samples were analyzed for residue mass and bacterial community composition.After residue burial in the soil,the cumulative residue mass loss rates were 18,69,and 77%after 5,12,and 24 months,respectively.The release of residue nitrogen,phosphorus,and carbon followed a similar pattern as mass loss,but 79%of residue potassium was released after only 1 month.The abundance,richness,and community diversity of bacteria in the residue increased rapidly and peaked after 9 or 20 months.Residue decomposition was mainly influenced by temperature and chemical composition in the early stage,and was influenced by chemical composition in the later stage.Phyla Actinobacteria,Bacteroidetes,and Firmicutes dominated the bacterial community composition in residue in the early stage,and the abundances of phyla Chloroflexi,Acidobacteria,and Saccharibacteria gradually increased in the later stage of decomposition.In conclusion,maize residue decomposition in soil was greatly influenced by temperature and residue composition in Northeast China,and the bacterial community shifted from dominance of copiotrophic populations in the early stage to an increase in oligotrophic populations in the later stage.

Comparative analysis on microbial community associated with different gastrointestinal regions of wild northern snakehead Channa argus Cantor, 1842

Microbial communities in different gastrointestinal regions （stomach, foregut, midgut, and hindgut） of the northern snakehead Channa argus （Cantor, 1842） were compared by polymerase chain reaction and partial 16S rDNA sequencing. A total of 194, 140, 212, and 122 OTUs were detected in the stomach, foregut, midgut, and hindgut, respectively. Significant differences were found in the Sobs, ACE, Shannon, and Simpson indices among samples （P〈0.05）. The gastrointestinal microbial community of C. argus consisted predominantly of Proteobacteria with either Halomonas, Shewanella, Plesiomonas, or Sphingomonas. Fusobacteria, Firm!cutes, and Bacteroidetes also existed in the gastrointestinal tracts. However, significant＇differences were found in the compositions of microbial community among the four regions （P〈0.05）. Cyanobacteria and Spirochetes were significantly higher in the midgut and hindgut （P〈0.05）. Fusobacteria and Firmicutes were dominant in the hindgut and foregut, respectively （P〈0.05）. Proteobacteria was the lowest in the hindgut （P〈0.05）. At genus level, Cetobacterium and Plesiomonas were significantly higher in the hindgut than in the other three samples （P〈0.05）. Clostridium and Prevotella were the highest in the midgut （P〈0.05）. Halomonas, Shewanella, and Sphingomonas were the highest in the foregut （P〈0.05）. Paracoccus and Vibrio were the highest in the stomach. Several genera were only detected in certain regions, as follows： stomach, Paracoccus and Hbrio; foregut, Halomonas, Shewanella, and Sphingomonas; midgut, Clostridium and Prevotella; and hindgut, Cetobacterium and Plesiomonas （P〈0.05）. At the species level, Acinetobacter rhizosphaerae was only detected in the stomach. Prevotella copri and Clostridium perfring were not detected in the foregut and midgut, respectively, whereas Prevotella copri and Faecalibacterium pra were not detected in the hindgut. These findings provide valuable information on the microbial community in each gastrointestinal region of C. argus. Moreover, this study indicated that microbial community was not only related to rearing environment but also to the physico-chemical characteristics of each gastrointestinal region.

Microbial Community Diversity and Vertical Distribution in a Columnar Sediment of Maluku Strait

The sediment samples were collected from Maluku Strait at a depth of 1250 m, which is influenced by Mindanao Current and Indonesian Throughflow. Based on 16S rRNA clone libraries, the community structure and vertical distribution of archaea and bacteria were studied in a columnar sediment of 2m in length. From the surface sediment, 16S sequences were derived from fourteen bacterial phyla (Gammaproteobacteria, Planctomycetes, Alphaproteobacteria, Deltproteobacteria were dominant), but were limited to two groups of archaea: Crenarchaeota (99%) and Euryarchaeota (1%). Besides, 90% of the archaea clones were ammonia oxidation-related which indicated that the ammonia-oxidizing archaea might make a significant contribution to the chemosynthesis in the surface sediment. Contrastively in the bottom sediment, six bacterial phylogenetic groups were obtained (Gammaproteobacteria and Firmicutes were absolutely dominant), however no archaea 16S rRNA was detected. The microbial diversity of surface sediment was much higher than the bottom and seven unique bacterial phyla were obtained from two sediment respectively. The geochemical elements analysis revealed that the content of C, TOC and S in the surface sediment was much higher than the bottom, but the content of P is contrary. The microbial communities might be in response to the geochemical substance transfer and deposit influenced by the ocean current and it deserves further study compared with the other sediment samples in this area.

Soil fungistasis and its relations to soil microbial composition and diversity:A case study of a series of soils with different fungistasis

Fungistasis is one of the important approaches to control soil-borne plant pathogens.Some hypotheses about the mechanisms for soil fungistasis had been established,which mainly focused on the soil bacterial community composition,structure,diversity as well as function.In this study,the bacterial community composition and diversity of a series of soils treated by autoclaving,which coming from the same original soil sample and showing gradient fungistasis to the target soil-borne pathogen fungi Fusarium grami...

Geochemical and microbial characters of sediment from the gas hydrate area in the Taixinan Basin, South China Sea

The Taixinan Basin is one of the most potential gas hydrate bearing areas in the South China Sea and abundant gas hydrates have been discovered during expedition in 2013. In this study, geochemical and microbial methods are combinedly used to characterize the sediments from a shallow piston Core DH_CL_11（gas hydrate free） and a gas hydrate-bearing drilling Core GMGS2-16 in this basin. Geochemical analyses indicate that anaerobic oxidation of methane（AOM） which is speculated to be linked to the ongoing gas hydrate dissociation is taking place in Core DH_CL_11 at deep. For Core GMGS2-16, AOM related to past episodes of methane seepage are suggested to dominate during its diagenetic process; while the relatively enriched δ18O bulk-sediment values indicate that methane involved in AOM might be released from the ＂episodic dissociation＂ of gas hydrate.Microbial analyses indicate that the predominant phyla in the bacterial communities are Firmicutes and Proteobacteria（Gammaproteobacteria and Epsilonproteobacteria）, while the dominant taxa in the archaeal communities are Marine_Benthic_Group_B（MBGB）, Halobacteria, Thermoplasmata, Methanobacteria,Methanomicrobia, Group C3 and MCG. Under parallel experimental operations, comparable dominant members（Firmicutes and MBGB） are found in the piston Core DH_CL_11 and the near surface layer of the long drilling Core GMGS2-16. Moreover, these members have been found predominant in other known gas hydrate bearing cores, and the dominant of MBGB has even been found significantly related to gas hydrate occurrence. Therefore,a high possibility for the existing of gas hydrate underlying Core DH_CL_11 is inferred, which is consistent with the geochemical analyses. In all, combined geochemical and microbiological analyses are more informative in characterizing sediments from gas hydrate-associated areas in the South China Sea.

Vegetation cover of the lahar valley on the Sarychev Peak volcano(Matua Isl.,Middle Kuril Islands) after the Eruption in 2009: current state and features of succession processes

The paper presents the study of the vegetation recovery after the descent of the lahar during the eruption of the Sarychev Peak volcano(Matua Isl.,Middle Kuriles) in 2009.The works were carried out in 2017.It was found that during the secondary succession,plant communities,typical of the altitudinal zonation of the volcanic structure vegetation,are formed on lahar sediments in the following manner: the upper sections of the slope are occupied by sparse meadow and shrub vegetation,the middle are presented by shrub belt with a developed canopy,and the lower are representative of shrub large-grass belt.At the same time,the ordination analysis of the vegetation cover of the lahar valley by the detrended correspondence analysis(DCA) revealed the dispersion of the counting areas along the altitudinal gradient.This is opposite to that characteristic for both,the background communities on the slopes of the studied volcanic structure,and for communities in dynamical equilibrium of a typical altitude profile.Besides,directly correlating indicators of α-diversity of communities indicate the presence of open young communities at the stage of a complex grouping.Since the species Duschekia fruticosa which is an identifier in buried sites,forms communities in a state of dynamic equilibrium,with individuals of 40–50 years old,and at the time of the work,formed a canopy with individuals of 7–8 years old,a complete recovery of the communities of the lahar valley is possible in no less than 40 years.The acquired data on the recovery of vegetation on lahar contribute to the study of succession processes in the sites located in the zone of active volcanism.In addition,in this work,for the first time,the rates of restoration of the vegetation cover following its destruction as a result of burial by lahar products,are estimated.The specific features of this process are also considered.Employing the broad range of mathematical methods for quantitative analysis of indicators of young communities inhabiting the substrate makes it possible to identify patterns of vegetation formed during succession processes.The specifics of this organization are taken into account in this analysis.

Assessing the impact of fungicide enostroburin application on bacterial community in wheat phyllosphere

Fungicides have been used extensively for controlling fungal pathogens of plants. However, little is known regarding the effects that fungicides upon the indigenous bacterial communities within the plant phyllosphere. The aims of this study were to assess the impact of fungicide enostroburin upon bacterial communities in wheat phyllosphere. Culture-independent methodologies of 16S rDNA clone library and 16S rDNA directed polymerase chain reaction with denaturing gradient gel electrophoresis （PCR-DGGE） were used for monitoring the change of bacterial community. The 16S rDNA clone library and PCR-DGGE analysis both confirmed the microbial community of wheat plant phyllosphere were predominantly of the γ-Proteobacteria phyla. Results from PCR-DGGE analysis indicated a significant change in bacterial community structure within the phyllosphere following fungicide enostroburin application. Bands sequenced within control cultures were predominantly of Pseudomonas genus, but those bands sequenced in the treated samples were predominantly strains of Pantoea genus and Pseudomonas genus. Of interest was the appearance of two DGGE bands following fungicide treatment, one of which had sequence similarities （98%） to Pantoea sp. which might be a competitor of plant pathogens. This study revealed the wheat phyllosphere bacterial community composition and a shift in the bacterial community following fungicide enostroburin application.

Monitoring of microbial community structure and succession in the biohydrogen production reactor by denaturing gradient gel electrophoresis(DGGE)

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.

Partial function prediction of sulfate-reducing bacterial community from the rhizospheres of two typical coastal wetland plants in China

Sulfate-reducing bacteria(SRB)are ubiquitous anaerobic microorganisms that play signifi cant roles in the global biogeochemical cycle.Coastal wetlands,one of the major habitats of SRB,exhibit high sulfate-reducing activity and thus play signifi cant roles in organic carbon remineralization,benthic geochemical action,and plant-microbe interactions.Recent studies have provided credible evidence that the functional rather than the taxonomic composition of microbes responds more closely to environmental factors.Therefore,in this study,functional gene prediction based on PacBio single molecular real-time sequencing of 16S rDNA was applied to determine the sulfate-reducing and organic substrate-decomposing activities of SRB in the rhizospheres of two typical coastal wetland plants in North and South China:Zostera japonica and Scirpus mariqueter.To this end,some physicochemical characteristics of the sediments as well as the phylogenetic structure,community composition,diversity,and proportions of several functional genes of the SRB in the two plant rhizospheres were analyzed.The Z.japonic a meadow had a higher dissimilatory sulfate reduction capability than the S.mariqueter-comprising saltmarsh,owing to its larger proportion of SRB in the microbial community,larger proportions of functional genes involved in dissimilatory sulfate reduction,and the stronger ability of the SRB to degrade organic substrates completely.This study confi rmed the feasibility of applying microbial community function prediction in research on the metabolic features of SRB,which will be helpful for gaining new knowledge of the biogeochemical and ecological roles of these bacteria in coastal wetlands.

Comparative analysis of the gut microbiota of wild adult rats from nine district areas in Hainan,China

BACKGROUND Wild rats have the potential to hold zoonotic infectious agents that can spread to humans and cause disease.AIM To better understand the composition of gut bacterial communities in rats is essential for preventing and treating such diseases.As a tropical island located in the south of China,Hainan province has abundant rat species.Here,we examined the gut bacterial composition in wild adult rats from Hainan province.METHODS Fresh fecal samples were collected from 162 wild adult rats,including three species(Rattus norvegicus,Leopoldamys edwardsi,and Rattus losea),from nine regions of Hainan province between 2017-2018.RESULTS We analyzed the composition of gut microbiota using the 16S rRNA gene amplicon sequencing.We identified 4903 bacterial operational taxonomic units(30 phyla,175 families,and 498 genera),which vary between samples of different rat species in various habitats at various times of the year.In general,Firmicutes were the most abundant phyla,followed by Bacteroidetes(15.55%),Proteobacteria(6.13%),and Actinobacteria(4.02%).The genus Lactobacillus(20.08%),unidentified_Clostridiales(5.16%),Romboutsia(4.33%),unidentified_Ruminococcaceae(3.83%),Bacteroides(3.66%),Helicobacter(2.40%)and Streptococcus(2.37%)were dominant.CONCLUSION The composition and abundance of the gut microbial communities varied between rat species and locations.This work provides fundamental information to identify microbial communities useful for disease control in Hainan province.

Periodic Addition of Glucose Suppressed Cyanobacterial Abundance in Additive Lake Water Samples during the Entire Bloom Season

Previously, we showed that prophylactic addition of glucose to Harsha Lake water samples could inhibit cyanobacteria growth, at least for a short period of time. The current study tested cyanobacterial control with glucose for the entire Harsha Lake bloom season. Water samples (1000 ml) were collected weekly from Harsha Lake during the algal-bloom season starting June 9 and lasting until August 24, 2022. To each of two 7-liter polypropylene containers, 500 ml of Harsha Lake water was added, and the containers were placed in a controlled environment chamber. To one container labeled “Treated,” 0.15 g of glucose was added, and nothing was added to the container labeled “Control.” After that, three 25 ml samples from each container were collected and used for 16S rRNA gene sequencing each week. Then 1000 ml of Harsha Lake water was newly collected each week, with 500 ml added to each container, along with the addition of 0.15 g glucose to the “Treated” container. Sequencing data were used to examine differences in the composition of bacterial communities between Treated and Control containers. Treatment with glucose altered the microbial communities by 1) reducing taxonomic diversity, 2) largely eliminating cyanobacterial taxa, and 3) increasing the relative abundance of subsets of non-cyanobacterial taxa (such as Proteobacteria and Actinobacteriota). These effects were observed across time despite weekly inputs derived directly from Lake water. The addition of glucose to a container receiving weekly additions of Lake water suppressed the cyanobacterial populations during the entire summer bloom season. The glucose appears to stimulate the diversity of certain bacterial taxa at the expense of the cyanobacteria.

Soil microbial community structure and function responses to successive planting of Eucalyptus

Many studies have shown soil degradation after the conversion of native forests to exotic Eucalyptus plantations. However, few studies have investigated the long-term impacts of short-rotation forestry practices on soil microorganisms. The impacts of Eucalyptus successive rotations on soil microbial communities were evaluated by comparing phospholipid fatty acid （PLFA） abundances, compositions, and enzyme activities of native Pinus massoniana plantations and adjacent 1st, 2nd, 3rd, 4th generation Eucalyptus plantations. The conversion from P. massoniana to Eucalyptus plantations significantly decreased soil microbial community size and enzyme activities, and increased microbial physiological stress. However, the PLFA abundances formed ＂U＂ shaped quadratic functions with Eucalyptus plantation age. Alternatively, physiological stress biomarkers, the ratios of monounsaturated to saturated fatty acid and Gram＋ to Gram- bacteria, formed ＂∩＂ shaped quadratic functions, and the ratio of cy17：0 to 16： 1ω7c decreased with plantation age. The activities of phenol oxidase, peroxidase, and acid phosphatase increased with Eucalyptus plantation age, while the cellobiobydrolase activity formed ＂U＂ shaped quadratic functions. Soil N：P, alkaline hydrolytic nitrogen, soil organic carbon, and understory cover largely explained the variation in PLFA profiles while soil N：P, alkaline hydrolytic nitrogen, and understory cover explained most of the variability in enzyme activity. In conclusion, soil microbial structure and function under Eucalyptus plantations were strongly impacted by plantation age. Most of the changes could be explained by altered soil resource availability and understory cover associated with successive planting of Eucalyptus. Our results highlight the importance of plantation age for assessing the impacts of plantation conversion as well as the importance of reducing disturbance for plantation management.

Influence of microbial community structure of seed sludge on the properties of aerobic nitrifying granules

In order to evaluate the influence of microbial community structure of seed sludge on the properties of aerobic nitrifying granules, these granules were cultivated with different seed sludge, and the variation of microbial community and dominant bacterial groups that impact the nitrogen removal efficiency of the aerobic nitrifying granules were analyzed and identified using 16 s rDNA sequence and denaturing gradient gel electrophoresis（DGGE） profiles. The results presented here demonstrated that the influence of the community structure of seed sludge on the properties of aerobic nitrifying granules was remarkable, and the granules cultivated by activated sludge from a beer wastewater treatment plant showed better performance, with a stable sludge volume index（SVI） value of 20 m L/g, high extracellular polymeric substance（EPS） content of 183.3 mg/L, high NH4＋-N removal rate of 89.42% and abundant microbial population with 10 dominant bacterial groups. This indicated that activated sludge with abundant communities is suitable for use as seed sludge in culturing aerobic nitrifying granules.