Project description:Intense bottom-ice algal blooms, often dominated by diatoms, are an important source of food for grazers, organic matter for export during sea ice melt, and dissolved organic carbon. Sea-ice diatoms have a number of adaptations, including accumulation of compatible solutes, that allow them to inhabit this highly variable environment characterized by extremes in temperature, salinity, and light. In addition to protecting them from extreme conditions, these compounds present a labile, nutrient-rich source of organic matter and include precursors to climate active compounds (e.g. DMS), which are likely regulated with environmental change. Here, intracellular concentrations of 45 metabolites were quantified in three sea-ice diatom species and were compared to two temperate diatom species, with a focus on compatible solutes and free amino acid pools. There was a large diversity of metabolite concentrations between diatoms with no clear pattern identifiable for sea-ice species. Concentrations of some compatible solutes (isethionic acid, homarine) approached 1 M in the sea-ice diatoms, Fragilariopsis cylindrus and Navicula cf. perminuta, but not in the larger sea-ice diatom, Nitzschia lecointei or in the temperate diatom species. The differential use of compatible solutes in sea-ice diatoms suggest different adaptive strategies and highlights which small organic compounds may be important in polar biogeochemical cycles.
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. Three different soil types from the Canadian high Arctic were sampled at two depths within the active layer of soil and at two sampling dates (winter and summer conditions), for a total of 20 samples.
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:The objective of this study was to identify the different functional genes involved in key biogeochemical cycles in the low Arctic regions. Understanding the microbial diversity in the Arctic region is an important step to determine the effects of climate change on these areas.
Project description:C5aR1, a receptor for the complement activation proinflammatory fragment, C5a, is primarily expressed on cells of the myeloid lineage, and to a lesser extent on endothelial cells and neurons in brain. Previous work demonstrated C5aR1 antagonist, PMX205, decreased amyloid pathology and suppressed cognitive deficits in Alzheimer Disease (AD) mouse models. In the Arctic AD mouse model, genetic deletion of C5aR1 prevented behavior deficits at 10 months. However, the molecular mechanisms of this protection has not been definitively demonstrated. To understand the role of microglial C5aR1 in the Arctic AD mouse model, we have taken advantage of the CX3CR1GFP and CCR2RFP reporter mice to distinguish microglia as GFP-positive and infiltrating monocytes as GFP and RFP positive, for subsequent transcriptome analysis on specifically sorted myeloid populations from wild type and AD mouse models. Immunohistochemical analysis of mice aged to 2, 5, 7 and 10 months showed no change in amyloid beta (Ab) deposition in the Arctic C5aR1 knockout (KO) mice relative to that seen in the Arctic mice. Of importance, no CCR2+ monocytes/macrophages were found near the plaques in the Arctic brain with or without C5aR1. RNA-seq analysis on microglia from these mice identified inflammation related genes as differentially expressed, with increased expression in the Arctic mice relative to wildtype and decreased expression in the Arctic/C5aR1KO relative to Arctic. In addition, phagosomal-lysosomal proteins and protein degradation pathways that were increased in the Arctic mice were further increased in the Arctic/C5aR1KO mice. These data are consistent with a microglial polarization state with restricted induction of inflammatory genes and enhancement of clearance pathways.
Project description:Analysis of microbial community composition in arctic tundra and boreal forest soils using serial analysis of ribosomal sequence tags (SARST). Keywords: other