Project description:Analysis of microbial community composition in arctic tundra and boreal forest soils using serial analysis of ribosomal sequence tags (SARST). Keywords: other
2004-01-12 | GSE949 | GEO
Project description:Fungal community composition boreal forest undergoing permafrost thaw
Project description:Because of severe abiotic limitations, Antarctic soils represent simplified ecosystems, where microorganisms are the principle drivers of nutrient cycling. This relative simplicity makes these ecosystems particularly vulnerable to perturbations, like global warming, and the Antarctic Peninsula is among the most rapidly warming regions on the planet. However, the consequences of the ongoing warming of Antarctica on microorganisms and the processes they mediate are unknown. Here, using 16S rRNA gene pyrosequencing and qPCR, we report a number of highly consistent changes in microbial community structure and abundance across very disparate sub-Antarctic and Antarctic environments following three years of experimental field warming (+ 0.5-2°C). Specifically, we found significant increases in the abundance of fungi and bacteria and in the Alphaproteobacteria-to-Acidobacteria ratio. These alterations were linked to a significant increase in soil respiration. Furthermore, the shifts toward generalist or opportunistic bacterial communities following warming weakened the linkage between bacterial diversity and functional diversity. Warming also increased the abundance of some organisms related to the N-cycle, detected as an increase in the relative abundance of nitrogenase genes via GeoChip microarray analyses. Our results demonstrate that soil microorganisms across a range of sub-Antarctic and Antarctic environments can respond consistently and rapidly to increasing temperatures, thereby potentially disrupting soil functioning. We conducted in situ warming experiments for three years using open-top chambers (OTCs) at one sub-Antarctic (Falkland Islands, 52ºS) and two Antarctic locations (Signy and Anchorage Islands, 60ºS and 67ºS respectively) (see Supplementary Fig. 1 for a map). OTCs increased annual soil temperature by an average of 0.8°C (at a depth of 5 cm), resulting in 8-43% increase in positive-degree days annually and a decrease in freeze-thaw cycle frequency by an average of 15 cycles per year (8). At each location, we included densely vegetated and bare fell-field soils in the experimental design for a total of six environments. Densely vegetated and bare environments represent two contrasting environments for Antarctic soil microorganisms, with large differences in terms of C and N inputs to soils. Massively parallel pyrosequencing (Roche 454 GS FLX Titanium) of 16S rRNA gene amplicons was used to follow bacterial diversity and community composition [GenBank Accession Numbers: HM641909-HM744649], and functional gene microarrays (GeoChip 2.0)(11) were used to assess changes in functional gene distribution. Bacterial and fungal communities were also quantified using real-time PCR.
Project description:<p>Drought stress negatively impacts microbial activity, but the magnitude of stress responses are likely dependent on a diversity of below ground interactions. Populus trichocarpa individuals and no plant bulk soils were exposed to extended drought (~0.03% gravimetric water content (GWC) after 12d), re-wet, and a 12-d 'recovery' period to determine the effects of plant presence in mediating soil microbiome stability to water stress. Plant metabolomic analyses indicated that drought exposure increased host investment in C and N metabolic pathways (amino acids, fatty-acids, phenolic glycosides) regardless of recovery. Several metabolites positively correlated with root-associated microbial alpha diversity, but not those of soil communities. Soil bacterial community composition shifted with P. trichocarpa presence and with drought relative to irrigated controls, whereas soil fungal composition only shifted with plant presence. However, root fungal communities strongly shifted with drought, whereas root bacterial communities changed to a lesser degree. The proportion of bacterial water-stress opportunistic OTUs (enriched counts in drought) were high (~11%) at the end of drying phases, and maintained after re-wet, and recovery phases in bulk soils, but declined over time in soils with plants present. For root fungi opportunistic OTUs were high at the end of recovery in drought treatments (~17% abundance), although relatively not responsive in soils, particularly planted soils (< 0.5% abundance for sensitive or opportunistic). These data indicate that plants modulate soil and root associated microbial drought responses via tight plant-microbe linkages during extreme drought scenarios, but trajectories after extreme drought vary with plant habitat and microbial functional groups.</p>
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.
2018-03-30 | GSE112489 | GEO
Project description:Bacterial diversity in disturbed forest
Project description:Here we have compared adult wildtype (N2) C. elegans gene expression when grown on different bacterial environments/fod sources in an effort to model naturally occuring nematode-bacteria interactions at the Konza Prairie. We hypothesize that human-induced changes to natural environments, such as the addition of nitrogen fertalizer, have effects on the bacterial community in soils and this drives downstream changes in the structure on soil bacterial-feeding nematode community structure. Here we have used transcriptional profiling to identify candidate genes involved in the interaction of nematodes and bacteria in nature.