Microbial Community Functional Diversity Research Articles

Spatiotemporal dynamics of marine bacterial and archaeal communities in surface waters off the northern Antarctic Peninsula

Seasonal changes in taxonomic and functional diversity of microbial communities in polar regions are commonly observed, requiring strategies of microbes to adapt to the corresponding changes in environmental conditions. These natural fluctuations form the backdrop for changes induced by anthropogenic impacts. The main goal of this study was to assess the seasonal and temporal changes in bacterial and archaeal diversity and community structure off the northern Antarctic Peninsula over several seasons (spring, summer, autumn) from 2013 to 2015. Ten monitoring stations were selected across the Gerlache and Bransfield Straits and nearby Elephant Island, and archaeal and bacterial communities examined by amplicon sequencing of 16S rRNA genes. Alpha-diversity indices were higher in spring and correlated significantly with temperature. Spring was characterized by the presence of SAR11, and microbial communities remaining from winter, including representatives of Thaumarchaeota (Nitrosopumilus), Euryarchaeota, members of Oceanospirillales, SAR324. Summer and autumn were characterized by a high prevalence of Flavobacteria (NS5 marine group and Polaribacter), Alphaproteobacteria (Rhodobacterales and SAR11 clade) and Gammaproteobacteria (Oceanospirillales/Balneatrix and Cellvibrionales), generally known to be associated with organic matter degradation. Relatively higher abundance of phytoplankton groups occurred in spring, mainly characterized by the presence of the haptophyte Phaeocystis and the diatom Corethron, influencing the succession of heterotrophic bacterial communities. Microbial diversity and community structure varied significantly over time, but not over space, i.e., were similar between monitoring stations for the same time. In addition, the observed interannual variability in microbial community structure might be related to an increase in sea surface temperature. Environmental conditions related to seasonal variation, including temperature and most likely phytoplankton derived organic matter, appear to have triggered the observed shifts in microbial communities in the waters off the northern Antarctic Peninsula.

Differences in carbon source usage by dental plaque in children with and without early childhood caries

Early childhood caries (ECC) is a considerable pediatric and public health problem worldwide. Preceding studies have focused primarily on bacterial diversity at the taxonomic level. Although these studies have provided significant information regarding the connection between dental caries and oral microbiomes, further comprehension of this microbial community’s ecological relevance is limited. This study identified the carbon source metabolic differences in dental plaque between children with and without ECC. We compared the microbial community functional diversity in 18 caries-free subjects with 18 severe ECC patients based on sole carbon source usage using a Biolog assay. The anaerobic microbial community in the ECC patients displayed greater metabolic activity than that of the control group. Specific carbon source metabolism differed significantly between the two groups. Subjects from the two groups were well distinguished by cluster and principal component analyses based on discriminative carbon sources. Our results implied that the microbial functional diversity between the ECC patients and healthy subjects differed significantly. In addition, the Biolog assay furthered our understanding of oral microbiomes as a composite of functional abilities, thus enabling us to identify the ecologically relevant functional differences among oral microbial communities.

Microbial Community Diversity and Differences in Cellar water of Typical Rainwater Harvesting Area

In order to explore the natural change mechanisms for cellar water quality for typical rainwater harvesting and drinking water surfaces in China, the MiSeq high-throughput sequencing method was used to study the differences between characteristics of microbial communities and functional diversity regarding collecting and making use of rainwater. This is achieved through constructing combined modes of different types of catchment areas and water-storing cellars. The results of this study show that there is significant differences in microbial community structure and function. The main factors causing this difference are heterogeneity of internal and external environmental factors regarding cellar water. The diversity of microbial community structures in cellar water show patterns of a large number of rare species and few common species. There are different significant microbial communities at different water points. The differences in the functional diversity of microbial communities shows that gene sequences that encode metabolic functions have significant advantages over other functional gene sequences, and amino acid, carbohydrate, lipid, energy, vitamin, terpenoid and polyketide, nucleotide, and glycan metabolism, as well as the biosynthesis of other secondary metabolites, are the main functional groups that compose metabolic function. This shows that there are a large number of microorganisms with relatively specific ecological functions in cellar water and many active metabolic activities are involved. Cellar water quality can be improved through combined modes of concrete collecting surfaces and water-storing cellars for collection and storage of rainwater. The results of the study aim to deepen the understanding of cellar water microbial community structures and diversity to be used as a reference for improving water quality and selecting the water surfaces for rainwater harvesting.

Dynamics of copper and tetracyclines during composting of water hyacinth biomass amended with peat or pig manure.

Composting is one of the post-treatment methods for phytoremediation plants. Due to a high potential of water hyacinth to accumulate pollutants, the physicochemical parameters, microbial activity as well as fates of copper (Cu) and tetracyclines (TCs) were investigated for the different amended water hyacinth biomass harvested from intensive livestock and poultry wastewater, including unamended water hyacinth (W), water hyacinth amended with peat (WP), and water hyacinth amended with pig manure (WPM) during the composting process. Pig manure application accelerated the composting process as evidenced by an increase of temperature, electrical conductivity (EC), NH4-N, as well as functional diversity of microbial communities compared to W and WP treatments. Composting process was slowed down by high Cu, but not by TCs. The addition of peat significantly increased the residual fraction of Cu, while pig manure addition increased available Cu concentration in the final compost. Cu could be effectively transformed into low available (oxidizable) and residual fractions after fermentation. In contrast, less than 0.5% of initial concentrations of TCs were determined at the end of 60-day composting for all treatments in the final composts. The dissipation of TCs was accelerated by the high Cu concentration during composting. Therefore, composting is an effective method for the post-treatment and resource utilization of phytoremediation plants containing Cu and/or TCs.

Crop rhizospheric microbial community structure and functional diversity as affected by maize and potato intercropping

ABSTRACTField trials were conducted to evaluate the effects of different cropping patterns (maize monocropping, maize and potato intercropping, potato monocropping) on microbial abundance, community structure, and microbial functional diversity using plate culture and Biolog technique. Results showed that compared with monocropping, intercropping increased the abundance of soil bacteria, fungi, and actinomyces in rhizosphere surrounding maize and potato. The average well color development (AWCD) and Shannon index (H) were higher in intercropping soil than that found in monocropping soil. The ability of rhizospheric soil microorganisms in utilizing six types of carbon sources had definite differences, and the most dominant community structure was the carbohydrates metabolic groups. Principal component analysis demonstrated that intercropping changed significantly soil microbial community functional diversity depending mainly on carbohydrates and carboxylic acids. Our findings suggested that maize–potato intercropping has positive effects on the improvement of soil microbial abundances, activity, and functional diversity.

Functional diversity of microbial communities in pristine aquifers inferred by PLFA- and sequencing-based approaches

Abstract. Microorganisms in groundwater play an important role in aquifer biogeochemical cycles and water quality. However, the mechanisms linking the functional diversity of microbial populations and the groundwater physico-chemistry are still not well understood due to the complexity of interactions between surface and subsurface. Within the framework of Hainich (north-western Thuringia, central Germany) Critical Zone Exploratory of the Collaborative Research Centre AquaDiva, we used the relative abundances of phospholipid-derived fatty acids (PLFAs) to link specific biochemical markers within the microbial communities to the spatio-temporal changes of the groundwater physico-chemistry. The functional diversities of the microbial communities were mainly correlated with groundwater chemistry, including dissolved O2, Fet and NH4+ concentrations. Abundances of PLFAs derived from eukaryotes and potential nitrite-oxidizing bacteria (11Me16:0 as biomarker for Nitrospira moscoviensis) were high at sites with elevated O2 concentration where groundwater recharge supplies bioavailable substrates. In anoxic groundwaters more rich in Fet, PLFAs abundant in sulfate-reducing bacteria (SRB), iron-reducing bacteria and fungi increased with Fet and HCO3− concentrations, suggesting the occurrence of active iron reduction and the possible role of fungi in meditating iron solubilization and transport in those aquifer domains. In more NH4+-rich anoxic groundwaters, anammox bacteria and SRB-derived PLFAs increased with NH4+ concentration, further evidencing the dependence of the anammox process on ammonium concentration and potential links between SRB and anammox bacteria. Additional support of the PLFA-based bacterial communities was found in DNA- and RNA-based Illumina MiSeq amplicon sequencing of bacterial 16S rRNA genes, which showed high predominance of nitrite-oxidizing bacteria Nitrospira, e.g. Nitrospira moscoviensis, in oxic aquifer zones and of anammox bacteria in more NH4+-rich anoxic groundwater. Higher relative abundances of sequence reads in the RNA-based datasets affiliated with iron-reducing bacteria in more Fet-rich groundwater supported the occurrence of active dissimilatory iron reduction. The functional diversity of the microbial communities in the biogeochemically distinct groundwater assemblages can be largely attributed to the redox conditions linked to changes in bioavailable substrates and input of substrates with the seepage. Our results demonstrate the power of complementary information derived from PLFA-based and sequencing-based approaches.

Ecotoxicological Assessment of Chemical Fumigants Utilising an Earthworm (Eisenia andrei) Bioassay and Soil Microbial Communities

Fumigation is an important crop protection practice employed to control soil pathogens and diseases. Metham sodium and cadusafos are two commonly used soil fumigants for this purpose. However, little information is available on their effects on non-target soil organisms. The aim of the study was to determine the ecotoxicity of these chemical fumigants on earthworms (organismal responses and DNA damage) and soil microbial communities. Changes in soil microbial community function and structure were evaluated by means of Biolog™ Ecoplates and phospholipid fatty acid (PLFA) analyses, respectively. Both fumigants had a significant (p < 0.05) negative impact on all earthworm endpoints. Earthworms did not reproduce; biomass was affected negatively and manifested significant DNA damage with metham sodium causing more pronounced effects in comparison to cadusafos. The fumigants had an inhibitory effect on microbial growth. No lasting effects were observed in the community structure but cadusafos had a pronounced effect on the microbial community functional diversity. Metham sodium and cadusafos had varying effects on earthworm and microbial endpoints. This illustrates the importance of using different bioindicators to get a better understanding of the overall effects on the soil ecosystem.

Linking the Belowground Microbial Composition, Diversity and Activity to Soilborne Disease Suppression and Growth Promotion of Tomato Amended with Biochar

Biochar, in addition to sequestering carbon, ameliorating soil, and improving plant performance, can impact foliar and soilborne plant diseases. Nevertheless, the mechanisms associated with suppression of soilborne diseases and improved plant performances are not well understood. This study is designed to establish the relationships between biochar-induced changes in rhizosphere microbial community structure, taxonomic and functional diversity, and activity with soilborne disease suppression and enhanced plant performance in a comprehensive fashion. Biochar suppressed Fusarium crown and root-rot of tomato and simultaneously improved tomato plant growth and physiological parameters. Furthermore, biochar reduced Fusarium root colonization and survival in soil, and increased the culturable counts of several biocontrol and plant growth promoting microorganisms. Illumina sequencing analyses of 16S rRNA gene revealed substantial differences in rhizosphere bacterial taxonomical composition between biochar-amended and non-amended treatments. Moreover, biochar amendment caused a significant increase in microbial taxonomic and functional diversity, microbial activities and an overall shift in carbon-source utilization. High microbial taxonomic and functional diversity and activity in the rhizosphere has been previously associated with suppression of diseases caused by soilborne pathogens and with plant growth promotion, and may collectively explain the significant reduction of disease and improvement in plant performance observed in the presence of biochar.

Biodegradation of pentachloronitrobenzene by Cupriavidus sp. YNS-85 and its potential for remediation of contaminated soils.

Pentachloronitrobenzene (PCNB) is a toxic chlorinated nitroaromatic compound. However, only a few bacteria have been reported to be able to utilize PCNB. In the present study, one pentachloronitrobenzene (PCNB)-degrading bacterium, Cupriavidus sp. YNS-85, was isolated from a contaminated Panax notoginseng plantation. The strain co-metabolized 200mgL-1 PCNB in aqueous solution with a removal rate of 73.8% after 5days. The bacterium also degraded PCNB effectively under acid conditions (pH4-6) and showed resistance to toxic trace elements (arsenic, copper, and cadmium). Its ability to utilize proposed PCNB intermediates as sole carbon sources was also confirmed. The soil microcosm experiment further demonstrated that bacterial bioaugmentation enhanced the removal of PCNB (37.8%) from soil and the accumulation of pentachloroaniline (89.3%) after 30days. Soil enzyme activity and microbial community functional diversity were positively influenced after bioremediation. These findings indicate that Cupriavidus sp. YNS-85 may be a suitable inoculant for in situ bioremediation of PCNB-polluted sites, especially those with acid soils co-contaminated with heavy metal(loid)s.

Changes in Soil Microbial Community Structure and Functional Diversity in the Rhizosphere Surrounding Tea and Soybean

Field trial was conducted to evaluate the effects of different planting patterns (tea monocropping, tea and soybean intercropping, soybean monocropping) on microbial community structure and microbial functional diversity using Biolog technique. Results showed that intercropping treatment exhibited higher average well color development (AWCD), diversity indices and community functional diversity as compared with monocropping. The microbial utilization of 6 types of carbon source indicated some differences. Principal component analysis and cluster analysis demonstrated that intercropping treatment significantly changed the functional diversity of the soil microbial community, mainly depending on carbohydrates and carboxylic acids. Our findings suggested that soil microbial metabolic activities and functional diversity were significantly changed by tea-soybean intercropping.

氮磷添加对亚热带常绿阔叶林土壤微生物群落特征的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 氮磷添加对亚热带常绿阔叶林土壤微生物群落特征的影响 DOI: 10.5846/stxb201611012225 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31370626，31070588）；国家“973”计划项目（2012CB416905） Effects of nitrogen and phosphorus addition on soil microbial community characteristics in a subtropical evergreen broadleaved forest Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了探讨氮磷添加对土壤微生物特点的影响，选择安徽省池州仙寓山常绿阔叶老龄林，设定了4个水平的氮磷添加试验，即对照（CK，0 kg N/hm2）、低氮（LN，50 kg N/hm2）、高氮（HN，100 kg N/hm2）、高氮+磷（HN+P，100 kg N/hm2+50 kg P/hm2）。利用氯仿熏蒸法和Biolog微平板技术，分析不同水平氮磷添加对不同土层（0-10 cm、10-20 cm和20-30 cm）土壤微生物生物量C（MBC）、N（MBN）和微生物群落功能多样性的影响。结果表明：MBC、MBN随土层加深而降低，且差异性极显著，MBC与MBC/MBN比在氮磷添加后均表现出显著性差异；土壤微生物群落的代谢活性随土层加深而降低，HN与LN处理的土壤微生物活性最高；McIntosh、Shannon和Simpson多样性指数在不同土层和不同N、P添加水平上都存在差异，表层土壤微生物多样性指数差异性较为显著。土壤微生物对羧酸类、氨基酸类和碳水类碳源利用率最高；主成分分析显示不同土层的土壤微生物碳源利用上有明显的变化，表层土壤微生物碳源利用在不同N、P添加水平上有明显的空间变异性，其他土层分布较为集中，空间差异性主要表现在对碳水类与羧酸类碳源的利用上。土层与氮、磷添加剂量对土壤微生物生物量C、N及功能多样性都有显著影响，其中高氮处理对表层土壤微生物影响最大。 Abstract:To reveal the effects of nitrogen and phosphorus addition on soil microbial characteristics, an old-growth evergreen broadleaved forest in the Xianyu Mountains in Chizhou of the Anhui Province was selected. Four treatments of nitrogen and phosphorus addition were designed, including a control (CK, 0 kg N/hm2), low nitrogen (LN, 50 kg N/hm2), high nitrogen (HN, 100 kg N/hm2), and high nitrogen + phosphorus (HN + P, 100 kg N/hm2 + 50 kg P/hm2) treatments. Microbial biomass carbon (MBC), biomass nitrogen (MBN), and microbial community functional diversity for different soil layers (0-10 cm, 10-20 cm, and 20-30 cm) were analyzed using the methods of chloroform-fumigation and the Biolog system. The results showed that MBC and MBN decreased with soil depth, with significant differences among soil layers (P > 0.05). The MBC and MBC/MBN ratio changed significantly after N and P addition. The metabolic activity of the soil microbial community also declined with soil depth. Soil microbial activities were highest in the HN and LN treatments. McIntosh, Shannon, and Simpson diversity indices differed in different soil layers and at different dosages of N and P. Microbial diversity indices for the 0-10 cm soil layer were significantly different among treatments. Carbon source utilization by soil microbes was highest for carboxylic acids, amino acids, and carbohydrates. The results of principal component analysis showed that carbon source utilization was different among the soil layers. There was significant spatial variability in carbon source utilization in the upper 0-10 cm of soil under different N and P treatments, whereas it was relatively stable in other soil layers (10-30 cm). This spatial heterogeneity was mainly manifested in carbon source utilization of carbohydrates and carboxylic acid. In general, the soil layer and N and P treatments had significant impacts on MBC, MBN, and soil microbial functional diversity, with greatest impacts occurring on the surface soil with high N treatment. 参考文献 相似文献 引证文献

不同油葵品种对盐碱地根际土壤酶活性及微生物群落功能多样性的影响

不同油葵品种对盐碱地根际土壤酶活性及微生物群落功能多样性的影响

Activity and functional diversity of microbial communities in long-term hydrocarbon and heavy metal contaminated soils

AbstractThe impacts of long-term polycyclic aromatic hydrocarbons (PAHs) and heavy metal pollution on soil microbial communities functioning were studied in soils taken from an old coke plant. The concentrations of PAHs in the tested soils ranged from 171 to 2137 mg kg-1. From the group of tested heavy metals, concentrations of lead were found to be the highest, ranging from 57 to 3478 mg kg-1, while zinc concentrations varied from 247 to 704 mg kg-1and nickel from 10 to 666 mg kg-1. High dehydrogenase, acid and alkaline phosphatase activities were observed in the most contaminated soil. This may indicate bacterial adaptation to long-term heavy metal and hydrocarbon contamination. However, the Community Level Physiological Profiles (CLPPs) analysis showed that the microbial functional diversity was reduced and influenced to a higher extent by some metals (Pb, Ni), moisture and conductivity than by PAHs.

Rhizosphere microbial impacts of alleviating faba bean Fusarium wilt with inoculating AM fungi

Greenhouse pot trials were conducted to investigate the effects of arbuscular mycorrhizal fungus (Glomus mosseae, Glomus tortuosum, Glomus intraradices and Glomus etunicatum) inoculation on the seedling growth, occurance of Fusarium wilt, population of Fusarium oxysporum and rhizosphere microbial community functional diversity in faba bean rhizosphere soil. Results showed that after inoculation of G. mosseae, G. tortuosum, G. intraradices and G. etunicatum, the shoot and root fresh mass of faba bean seedlings increased significantly, the disease index of faba bean fusarium wilt decreased significantly by 94.0%, 60.0%, 64.0% and 94.0%, respectively, the amount of F. oxysporum of faba bean rhizosphere decreased significantly by 98.6%, 74.3%, 77.8% and 90.4%, respectively. The best inhibitory effects to Fusarium wilt were with G. mosseae and G. etunicatum treatments. Inoculation of G. mosseae, G. tortuosum and G. etunicatum significantly increased carbon sources utilization ability of carbohydrates, amino acids, carboxylic acids and phenolic acids, with the average well color development (AWCD) value being increased by 34.4%, 31.5% and 50.8% respectively, but such significant differences were not observed with inoculation of G. intraradice. Principal component analyses showed that inoculation of G. mosseae, G. tortuosum and G. etunicatum fungi changed the rhizospheric microbial community composition. Correlation analyses showed that the utilization of carbohydrates carbon sources (β-Methyl-D-glucoside, D-Galacturonic acid, D-Mannitol, N-Acetyl-D-Glucosamine, D-Cellobiose,) and carboxylic acids carbon sources (D-Galactonic acid-γ-Lactone) were significantly increased after inoculation of G. tortuosum, and the utilization of L-Arginine and 4-Hydroxy benzoic acid significantly increased after inoculation of G. mosseae and G. etunicatum. Carbohydrates, carboxylic acids were main carbon sources utilized by rhizosphere microbes after G. tortuosum and G. intraradices inoculation, and amino acids and phenolic acids were main carbon sources utilized by rhizosphere microbes after G. mosseae and G. etunicatum inoculation. Inoculation of AM fungi significantly increased the activities of rhizosphere microbes, changed soil microbe community functional diversity, and thus inhibited the growth of F. oxysporum. The inhibitory impacts of AM fungi inoculations depended on the changes of microbes utilizing carbon sources.

Genomic and functional techniques to mine the microbiome for novel antimicrobials and antimicrobial resistance genes.

Microbial communities contain diverse bacteria that play important roles in every environment. Advances in sequencing and computational methodologies over the past decades have illuminated the phylogenetic and functional diversity of microbial communities from diverse habitats. Among the activities encoded in microbiomes are the abilities to synthesize and resist small molecules, yielding antimicrobial activity. These functions are of particular interest when viewed in light of the public health emergency posed by the increase in clinical antimicrobial resistance and the dwindling antimicrobial discovery and approval pipeline, and given the intimate ecological and evolutionary relationship between antimicrobial biosynthesis and resistance. Here, we review genomic and functional methods that have been developed for accessing the antimicrobial biosynthesis and resistance capacity of microbiomes and highlight outstanding examples of their applications.

Enzyme properties down the soil profile - A matter of substrate quality in rhizosphere and detritusphere

The decomposition of soil organic matter depends strongly on its availability to microorganisms and their enzymes. The rhizosphere and detritusphere are microbial hot spots due to additional substrate input, leading to high abundance, specific species diversity and functional diversity of microbial communities. However, rhizosphere and detritusphere differ in substrate quality, localization, and duration of input. We hypothesized that the contrasting substrate availability between rhizosphere and detritusphere affects the activity of microorganisms and associated enzymes. Organic carbon (C) from the rhizosphere and detritusphere decreases with soil depth and, consequently, microbial hot spots become rarer and competition for C and nutrients increases. In deeper soil (>40 cm depth) the amount and quality of substrates is expected to decrease and, therefore, the effect of contrasting substrate input to disappear. Plant N uptake is expected to reduce N availability in the rhizosphere of maize compared to the detritusphere and bare fallow. These hypotheses were tested in a factorial field experiment with 1) maize-planted, 2) maize litter-amended, and 3) bare sites. Enzyme kinetic parameters (Vmax, Km, Ka), extractable organic C and microbial biomass C were compared in soil affected by rhizosphere and detritusphere throughout the profile to 70 cm depth, to assess microbial C and nutrient limitations. A decrease in enzyme activity with depth due to resource scarcity and lower substrate quality appeared in planted and litter-amended soil. N limitation in planted soil increased the activity and substrate affinity of proteolytic enzymes to provide for microbial N demand through SOM decomposition. This was in line with lower Vmax ratios (Vmax for C-cycling enzymes divided by Vmax for N-cycling enzymes) in planted relative to litter-amended topsoil. The catalytic efficiency of enzymes decreased 2- to 20-fold from top- (<40 cm) to subsoil (>40 cm), irrespective of the substrate input. Substrate quality in the rhizosphere and detritusphere affected enzyme activities only in the topsoil, whereas a sharp decline of C input with depth led to similar activities in the subsoil. Most of the enzyme indexes reflected shifts in allocation of C and nutrients in the rhizosphere and detritusphere. The presented results underline the role of microorganisms as critical links in the C and nutrient transfers in the rhizosphere and detritusphere.

Temporal dynamics of fungal communities in soybean rhizosphere

Many biotic and abiotic factors influence the structural and functional diversity of microbial communities in the rhizosphere. This study aimed to understand the dynamics of fungal community in the soybean rhizosphere during soybean growth and directly compare the influence of abiotic and biotic factors in shaping the fungal communities across different growth periods. High-throughput sequencing based on internal transcribed spacer (ITS) region, quantitative PCR, and statistical analysis approaches were used to measure the fungal community structure, abundance, and dynamic changes of 63 rhizosphere soil samples which were taken from different fertilization regimes and rhizobium inoculation treatments during three soybean growth stages. Among the taxa examined, more than 16 fungal classes were detected from the 21 soil samples. Sordariomycetes was the most abundant class, followed by Dothideomycetes, Agaricomycetes, and Eurotiomycetes. Soybean growth stage was the most important factor determining the diversity patterns of the fungal communities. Fungal community diversity was closely related to the base-fertilizer application, and fungal community richness was associated with rhizobium inoculation. Beta diversity of the fungal community based on the Bray-Curtis distance was significantly related to plant growth stage. Network analysis showed that mutual cooperation among fungal taxa became more intimate during the plant growth. Compared with edaphic properties, plant growth stage was the dominant factor in determining soil fungal community dynamics. Base-fertilizer and rhizobium inoculation affected the alpha diversity of the soil fungi.

Soil microbial community profiles and functional diversity in limestone cedar glades

Rock outcrop ecosystems, such as limestone cedar glades (LCGs), are known for their rare and endemic plant species adapted to high levels of abiotic stress. Soils in LCGs are thin (<25cm), soil-moisture conditions fluctuate seasonally between xeric and saturated, and summer soil temperatures commonly exceed 48°C. The effects of these stressors on soil microbial communities (SMC) remain largely unstudied, despite the importance of SMC-plant interactions in regulating the structure and function of terrestrial ecosystems. SMC profiles and functional diversity were characterized in LCGs using community level physiological profiling (CLPP) and plate-dilution frequency assays (PDFA). Most-probable number (MPN) estimates and microbial substrate-utilization diversity (H) were positively related to soil thickness, soil organic matter (OM), soil water content, and vegetation density, and were diminished in alkaline soil relative to circumneutral soil. Soil nitrate showed no relationship to SMCs, suggesting lack of N-limitation. Canonical correlation analysis indicated strong correlations between microbial CLPP patterns and several physical and chemical properties of soil, primarily temperature at the ground surface and at 4-cm depth, and secondarily soil-water content, enabling differentiation by season. Thus, it was demonstrated that several well-described abiotic determinants of plant community structure in this ecosystem are also reflected in SMC profiles.

Impact of plant species on spatial distribution of metabolic potential and functional diversity of microbial communities in a constructed wetland treating aquaculture wastewater

Two horizontal subsurface flow constructed wetlands, one planted with Iris pseudacorus (HF1) and the other with Phragmites australis (HF2), were built to treat aquaculture wastewater. Pollutants removal, especially the nitrogen removal efficiency, as well as the activities, metabolism, and functional diversities of the microbial communities involved were evaluated under different conditions. NO3−-N was removed in HF1 in all seasons, while it accumulated during autumn and winter in HF2. HF2 was more efficient at removing NH4+-N than HF1 in spring and summer when HRT was above 2 d. Nitrification intensity was higher in HF2, while denitrification intensity was higher in HF1. Biolog-ECO indicated that microbial diversity was higher in HF1 than in HF2, and the structure of the microbial community was more different at the back end and in the lower layer than at other places. These results were further confirmed by qPCR and 454-pyrosequencing. The relative abundances of Nitrospira were highest in back end of the upper layer in HF2, while Denitratisoma, which involves in denitrification, was mainly found in the lower layer of HF1. The results illustrated that the radial oxygen loss from P. australis and root exudates of I. pseudacorus could have an impact on the nitrogen removal efficiency by influencing the development of microbial communities.

Microbial community metabolic function in constructed wetland mesocosms treating the pesticides imazalil and tebuconazole

The objective of this research was to study the differences in microbial community metabolic function in planted and unplanted saturated constructed wetland mesocosm systems with five different wetland plant species, Typha latifolia, Phragmites australis, Iris pseudacorus, Berula erecta and Juncus effusus treating the pesticides imazalil and tebuconazole. Community level physiological profiling (CLPP) was used to determine the microbial community metabolic function from each mesocosm. Microbial activity and metabolic richness were in general not differentiated by pesticides presence. Significantly lower values in comparison with a non-pesticide control were only found in the Iris mesocosms exposed to imazalil and tebuconazole and in the Berula mesocosms exposed to tebuconazole during winter. Planted mesocosms had different microbial community carbon source utilization patterns in comparison to the unplanted mesocosms. In comparison to pesticide presence, plant species had a larger effect on differentiating the microbial community carbon source utilization patterns. Seasonal effects on carbon source utilization patterns were observed for both planted and unplanted mesocosms. In summer, microbial activity and metabolic richness were negatively correlated with TN, NH4+-N, TP concentration and pH in the control group, but not in the pesticide treatment groups, again suggesting a microbial community functional shift in the presence of pesticides. The main factors driving microbial community activity and functional diversity were plant species and season, while carbon source utilization revealed some pesticide adaptation in the summer period.