Project description:Methanococcus maripaludis utilizes selenocysteine-(Sec-) containing proteins (selenoproteins), mostly active in the organism’s primary energy metabolism, methanogenesis. Under selenium depletion, M. maripaludis employs a set of enzymes containing cysteine (Cys) instead of Sec. The genes coding for these Sec-/Cys-containing isoforms are the only genes known expression of which is influenced by the selenium status of the cell. Using quantitative proteomics and transcriptomics approx. 7% and 12%, respectively, of all genes/proteins were differentially expressed/synthesized in response to the selenium supply. Some of the genes identified involve methanogenesis, nitrogenase functions, and putative transporters. An increase of transcript abundance for putative transporters under selenium-depleted conditions indicated the organism’s effort to tap into alternative sources of selenium. Selenium sources M. maripaludis is known to utilize are selenite and dimethylselenide. To expand this list, a selenium responsive reporter strain was assessed with nine other, environmentally relevant selenium species. While some had a similar biological window as selenite, others were effectively utilized at lower concentrations. Conversely, selenate and seleno-amino acids were only utilized at unphysiologically high concentrations and two compounds were not utilized at all. To address the role of the selenium-regulated putative transporters in selenium transport, M. maripaludis mutant strains lacking one or two of the putative transporters were tested for the capability to utilize the different selenium species. Of the five putative transporters analyzed by loss-of-function mutagenesis, none appeared to be absolutely required for utilizing any of the selenium species tested, indicating they have redundant and/or overlapping specificities, or are not dedicated selenium transporters.
Project description:Oxidation of cysteines by reactive oxygen species (ROS) initiates thermogenesis in brown and beige adipose tissues. Cellular selenols, where sulfur is replaced with selenium, exhibit enhanced reactivity with ROS. Here we developed a mass spectrometric method to interrogate incorporation of selenols into proteins. Unexpectedly, this approach revealed facultative incorporation of selenium into proteins that lack canonical encoding for selenium-containing amino acids. Selenium was selectively incorporated into regulatory sites on key metabolic proteins, including as selenocysteine replacing cysteine at position 253 in UCP1. Remarkably, dietary selenium supplementation elevated facultative incorporation into UCP1, elevated energy expenditure through thermogenic adipose tissue, and protected against obesity. Together, these findings reveal the existence of facultative protein selenation, which correlates with impacts on thermogenic adipocyte function.
Project description:Negatives effects induced by exposure to ultra-violet (UV) radiation are well known. Nevertheless the modes of action of UV radiation are not well understood, in particular in soil invertebrates. In the present work, the effects of two UV doses (mimicking worst case scenarios in earth crust) on gene expression profile of Enchytraeus crypticus (Enchytraeidae, Oligochaeta) were investigated using the high-throughput 4 x 44K microarray developed for the species.
Project description:Temperature is an important ecological condition, and sudden temperature changes in soil can induce stress in soil-dwelling invertebrates. Soil animals can move to more favorable habitats and/or adapt physiologically to a stressful environment. Hyperthermic conditions will impact gene expression as one of the first steps. We use a transcriptomics approach to identify the transcripts of which expression changed in response to heat stress in the springtail Folsomia candida using a 5,131 probe microarray. A temperature shift from 20°C to 30°C for 30 minutes significantly altered the expression of 142 genes, of which 116 were upregulated, and 26 downregulated. Many upregulated genes encoded heat shock proteins (Hsps) or enzymes involved in the synthesis of ATP, such as members of the electron transport chain. Furthermore, genes involved in oxidative stress and anion-transporting ATPases were upregulated. Downregulated were glycoside hydrolases, involved in catalysis of certain disaccharides, which indicate an accumulation of stress-protective disaccharides. The microarray results from this study, which were validated using quantitative RT PCR, reveal a mild response to heat shock in this soil invertebrate, relative to other organisms. This may be due to specific ecological factors during evolution of soil invertebrates, such as the relatively stable temperatures in the soil habitat. This study presents potential candidate genes for future functional studies concerning thermal stress in soil-dwelling invertebrates, like e.g., the investigation of the heat hardening process.
Project description:Temperature is an important ecological condition, and sudden temperature changes in soil can induce stress in soil-dwelling invertebrates. Soil animals can move to more favorable habitats and/or adapt physiologically to a stressful environment. Hyperthermic conditions will impact gene expression as one of the first steps. We use a transcriptomics approach to identify the transcripts of which expression changed in response to heat stress in the springtail Folsomia candida using a 5,131 probe microarray. A temperature shift from 20°C to 30°C for 30 minutes significantly altered the expression of 142 genes, of which 116 were upregulated, and 26 downregulated. Many upregulated genes encoded heat shock proteins (Hsps) or enzymes involved in the synthesis of ATP, such as members of the electron transport chain. Furthermore, genes involved in oxidative stress and anion-transporting ATPases were upregulated. Downregulated were glycoside hydrolases, involved in catalysis of certain disaccharides, which indicate an accumulation of stress-protective disaccharides. The microarray results from this study, which were validated using quantitative RT PCR, reveal a mild response to heat shock in this soil invertebrate, relative to other organisms. This may be due to specific ecological factors during evolution of soil invertebrates, such as the relatively stable temperatures in the soil habitat. This study presents potential candidate genes for future functional studies concerning thermal stress in soil-dwelling invertebrates, like e.g., the investigation of the heat hardening process. Folsomia candida was first acclimated to LUFA 2.2 soil at 20 C for two days. Then animals were either exposed to 30 C for 30 minutes (heat shock treated), or were not heat shocked (reference). For each treatment 4 biological replicates were used, replicate samples consisted of total RNA extracted from ~30 animals exposed in the same jar to either reference or heat shock. Each unique heat shock treated sample was hybridized to a unique reference sample. In total in 4 hybridizations of 8 samples, was performed. The dyes were evenly distributed, which means that for each treatment two samples were labeled with cy3 and the other two with cy5.
Project description:Microbial community analysis with DNA oligonucleotide microarrays targeting ribosomal RNA (rRNA) provides a highly parallel interrogation of nucleic acids isolated from environmental samples. High fidelity readout is essential for accurate interpretation of hybridisations. We describe the hybridisation of in vitro transcribed 16S rRNA from an uncontaminated and 2,4,6-trinitrotoluene contaminated soil to an oligonucleotide microarray containing group- and species-specific perfect match (PM) probes and their 2 corresponding mismatch (MM) probes. Thermal dissociation analysis was used to determine the specificity of each PM-MM probe set. Functional ANOVA often discriminated PM-MM probe sets when Td values (temperature at 50% probe-target dissociation) could not. Maximum discrimination for many PM and MM probes often occurred at temperatures greater than the Td. Comparison of signal intensities measured prior to dissociation analysis from hybridisations of the two soil samples revealed significant differences in domain-, group- and species-specific probes. Functional ANOVA showed significantly different dissociation curves for 11 PM probes when hybridisations from the two soil samples were compared, even though initial signal intensities for 3 of the 11 did not vary. This approach provides a highly parallel, multi-level analysis that incorporates MM probes and dissociation curves into high fidelity microarray analysis of complex environmental nucleic acid profiles. Keywords: Microbial diversity, thermal dissociation analysis
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:Investigation of the phylogenetic diversity of Acidobacteria taxa using PCR amplicons from positive control 16S rRNA templates and total genomic DNA extracted from soil and a soil clay fraction