Project description:Peatlands of the Lehstenbach catchment (Germany) house so far unidentified microorganisms with phylogenetically novel variants of the dissimilatory (bi)sulfite reductase genes dsrAB. These genes are characteristic for microorganisms that reduce sulfate, sulfite, or some organosulfonates for energy conservation, but can also be present in anaerobic syntrophs. However, nothing is currently known regarding the abundance, community dynamics, and biogeography of these dsrAB-carrying microorganisms in peatlands. To tackle these issues, soils from a Lehstenbach catchment site (Schlöppnerbrunnen II fen) from different depths were sampled at three time points over a six-year period to analyze the diversity and distribution of dsrAB-containing microorganisms by a newly developed functional gene microarray and quantitative PCR assays. Members of novel, uncultivated dsrAB lineages (approximately representing species-level groups) (i) dominated a temporally stable but spatially structured dsrAB community and (ii) represented ‘core’ members (up to 1-1.7% relative abundance) of the autochthonous microbial community in this fen. In addition, denaturing gradient gel electrophoresis (DGGE)- and clone library-based comparison of the dsrAB diversity in soils from a wet meadow, three bogs, and five fens of various geographic locations (distance ~1-400 km), identified one Syntrophobacter-related and nine novel dsrAB lineages to be widespread in low-sulfate peatlands. Signatures of biogeography in dsrB-DGGE data were not correlated with geographic distance but could largely be explained by soil pH and wetland type, implying that distribution of dsrAB-carrying microorganisms in wetlands on the scale of a few hundred kilometers is not limited by dispersal but determined by contemporary environmental conditions. 36 dsrAB clones for chip evaluation, 33 hybridizations of labeled dsrAB RNA from environmental peatsoil samples
Project description:Peatlands of the Lehstenbach catchment (Germany) house so far unidentified microorganisms with phylogenetically novel variants of the dissimilatory (bi)sulfite reductase genes dsrAB. These genes are characteristic for microorganisms that reduce sulfate, sulfite, or some organosulfonates for energy conservation, but can also be present in anaerobic syntrophs. However, nothing is currently known regarding the abundance, community dynamics, and biogeography of these dsrAB-carrying microorganisms in peatlands. To tackle these issues, soils from a Lehstenbach catchment site (Schlöppnerbrunnen II fen) from different depths were sampled at three time points over a six-year period to analyze the diversity and distribution of dsrAB-containing microorganisms by a newly developed functional gene microarray and quantitative PCR assays. Members of novel, uncultivated dsrAB lineages (approximately representing species-level groups) (i) dominated a temporally stable but spatially structured dsrAB community and (ii) represented ‘core’ members (up to 1-1.7% relative abundance) of the autochthonous microbial community in this fen. In addition, denaturing gradient gel electrophoresis (DGGE)- and clone library-based comparison of the dsrAB diversity in soils from a wet meadow, three bogs, and five fens of various geographic locations (distance ~1-400 km), identified one Syntrophobacter-related and nine novel dsrAB lineages to be widespread in low-sulfate peatlands. Signatures of biogeography in dsrB-DGGE data were not correlated with geographic distance but could largely be explained by soil pH and wetland type, implying that distribution of dsrAB-carrying microorganisms in wetlands on the scale of a few hundred kilometers is not limited by dispersal but determined by contemporary environmental conditions.
Project description:Cropping soils vary in extent of natural suppression of soil-borne plant diseases. However, it is unknown whether similar variation occurs across pastoral agricultural systems. We examined soil microbial community properties known to be associated with disease suppression across 50 pastoral fields varying in management intensity. The composition and abundance of the disease-suppressive community were assessed from both taxonomic and functional perspectives.
Project description:Arsenic (As) bioavailability in the rice rhizosphere is influenced by many microbial interactions, particularly by metal-transforming functional groups at the root-soil interface. This study was conducted to examine As-transforming microbes and As-speciation in the rice rhizosphere compartments, in response to two different water management practices (continuous and intermittently flooded), established on fields with high to low soil-As concentration. Microbial functional gene composition in the rhizosphere and root-plaque compartments were characterized using the GeoChip 4.0 microarray. Arsenic speciation and concentrations were analyzed in the rhizosphere soil, root-plaque, porewater and grain samples. Results indicated that intermittent flooding significantly altered As-speciation in the rhizosphere, and reduced methyl-As and AsIII concentrations in the pore water, root-plaque and rice grain. Ordination and taxonomic analysis of detected gene-probes indicated that root-plaque and rhizosphere assembled significantly different metal-transforming functional groups. Taxonomic non-redundancy was evident, suggesting that As-reduction, -oxidation and -methylation processes were performed by different microbial groups. As-transformation was coupled to different biogeochemical cycling processes establishing functional non-redundancy of rice-rhizosphere microbiome in response to both rhizosphere compartmentalization and experimental treatments. This study confirmed diverse As-biotransformation at root-soil interface and provided novel insights on their responses to water management, which can be applied for mitigating As-bioavailability and accumulation in rice grains.
Project description:Anthropogenic nitrogen (N) deposition may affect soil organic carbon (SOC) decomposition, thus affecting the global terrestrial carbon (C) cycle. However, it remains unclear how the level of N deposition affects SOC decomposition by regulating microbial community composition and function, especially C-cycling functional genes structure. We investigated the effects of short-term N addition on soil microbial C-cycling functional gene composition, SOC-degrading enzyme activities, and CO2 emission in a 5-year field experiment established in an artificial Pinus tabulaeformis forest on the Loess Plateau, China.
Project description:The increased urban pressures are often associated with specialization of microbial communities. Microbial communities being a critical player in the geochemical processes, makes it important to identify key environmental parameters that influence the community structure and its function.In this proect we study the influence of land use type and environmental parameters on the structure and function of microbial communities. The present study was conducted in an urban catchment, where the metal and pollutants levels are under allowable limits. The overall goal of this study is to understand the role of engineered physicochemical environment on the structure and function of microbial communities in urban storm-water canals. Microbial community structure was determined using PhyoChio (G3) Water and sediment samples were collected after a rain event from Sungei Ulu Pandan watershed of >25km2, which has two major land use types: Residential and industrial. Samples were analyzed for physicochemical variables and microbial community structure and composition. Microbial community structure was determined using PhyoChio (G3)
Project description:The melting of permafrost and its potential impact on greenhouse gas emissions is a major concern in the context of global warming. The fate of the carbon trapped in permafrost will largely depend on soil physico-chemical characteristics, among which are the quality and quantity of organic matter, pH and water content, and on microbial community composition. In this study, we used microarrays and real-time PCR (qPCR) targeting 16S rRNA genes to characterize the bacterial communities in three different soil types representative of various Arctic settings. The microbiological data were linked to soil physico-chemical characteristics and CO2 production rates. Microarray results indicated that soil characteristics, and especially the soil pH, were important parameters in structuring the bacterial communities at the genera/species levels. Shifts in community structure were also visible at the phyla/class levels, with the soil CO2 production rate being positively correlated to the relative abundance of the Alphaproteobacteria, Bacteroidetes, and Betaproteobacteria. These results indicate that CO2 production in Arctic soils does not only depend on the environmental conditions, but also on the presence of specific groups of bacteria that have the capacity to actively degrade soil carbon.
Project description:Soil transplant serves as a proxy to simulate climate change in realistic climate regimes. Here, we assessed the effects of climate warming and cooling on soil microbial communities, which are key drivers in Earth’s biogeochemical cycles, four years after soil transplant over large transects from northern (N site) to central (NC site) and southern China (NS site) and vice versa. Four years after soil transplant, soil nitrogen components, microbial biomass, community phylogenetic and functional structures were altered. Microbial functional diversity, measured by a metagenomic tool named GeoChip, and phylogenetic diversity are increased with temperature, while microbial biomass were similar or decreased. Nevertheless, the effects of climate change was overridden by maize cropping, underscoring the need to disentangle them in research. Mantel tests and canonical correspondence analysis (CCA) demonstrated that vegetation, climatic factors (e.g., temperature and precipitation), soil nitrogen components and CO2 efflux were significantly correlated to the microbial community composition. Further investigation unveiled strong correlations between carbon cycling genes and CO2 efflux in bare soil but not cropped soil, and between nitrogen cycling genes and nitrification, which provides mechanistic understanding of these microbe-mediated processes and empowers an interesting possibility of incorporating bacterial gene abundance in greenhouse gas emission modeling.
Project description:Permafrost soil in high latitude tundra is one of the largest terrestrial carbon (C) stocks and is highly sensitive to climate warming. Understanding microbial responses to warming induced environmental changes is critical to evaluating their influence on soil biogeochemical cycles. In this study, a functional gene array (i.e. GeoChip 4.2) was used to analyze the functional capacities of soil microbial communities collected from a naturally degrading permafrost region in Central Alaska. Varied thaw history was reported to be the main driver of soil and plant differences across a gradient of minimally, moderately and extensively thawed sites. Compared with the minimally thawed site, the number of detected functional gene probes across the 15-65 cm depth profile at the moderately and extensively thawed sites decreased by 25 % and 5 %, while the community functional gene beta-diversity increased by 34% and 45%, respectively, revealing decreased functional gene richness but increased community heterogeneity along the thaw progression. Particularly, the moderately thawed site contained microbial communities with the highest abundances of many genes involved in prokaryotic C degradation, ammonification, and nitrification processes, but lower abundances of fungal C decomposition and anaerobic-related genes. Significant correlations were observed between functional gene abundance and vascular plant primary productivity, suggesting that plant growth and species composition could be co-evolving traits together with microbial community composition. Altogether, this study reveals the complex responses of microbial functional potentials to thaw related soil and plant changes, and provides information on potential microbially mediated biogeochemical cycles in tundra ecosystems.
Project description:The response of soil microbial community to climate warming through both function shift and composition reorganization may profoundly influence global nutrient cycles, leading to potential significant carbon release from the terrain to the atmosphere. Despite the observed carbon flux change in northern permafrost, it remains unclear how soil microbial community contributes to this ecosystem alteration. Here, we applied microarray-based GeoChip 4.0 to investigate the functional and compositional response of subsurface (15~25cm) soil microbial community under about one year’s artificial heating (+2°C) in the Carbon in Permafrost Experimental Heating Research site on Alaska’s moist acidic tundra. Statistical analyses of GeoChip signal intensities showed significant microbial function shift in AK samples. Detrended correspondence analysis and dissimilarity tests (MRPP and ANOSIM) indicated significant functional structure difference between the warmed and the control communities. ANOVA revealed that 60% of the 70 detected individual genes in carbon, nitrogen, phosphorous and sulfur cyclings were substantially increased (p<0.05) by heating. 18 out of 33 detected carbon degradation genes were more abundant in warming samples in AK site, regardless of the discrepancy of labile or recalcitrant C, indicating a high temperature sensitivity of carbon degradation genes in rich carbon pool environment. These results demonstrated a rapid response of northern permafrost soil microbial community to warming. Considering the large carbon storage in northern permafrost region, microbial activity in this region may cause dramatic positive feedback to climate change, which is important and necessary to be integrated into climate change models.