Project description:The abundance of bacterial (AOB) and archaeal (AOA) ammonia oxidisers, assessed using quantitative PCR measurements of their respective a-subunit of the ammonia monooxygenase (amoA) genes, and ammonia oxidation rates were measured in four contrasting coastal sediments in the Western English Channel. Sediment was sampled bimonthly from July 2008 to May 2011, and measurements of ammonia oxidiser abundance and activity compared to a range of environmental variables including salinity, temperature, water column nutrients and sediment carbon and nitrogen content. Despite a higher abundance of AOA amoA genes within all sediments, and at all time-points, rates of ammonia oxidation correlated with AOB and not AOA amoA gene abundance. Other than ammonia oxidation rate, sediment particle size was the only variable that correlated with the spatial and temporal patterns of AOB amoA gene abundance, implying a preference of the AOB for larger sediment particles. This is possibly due to deeper oxygen penetration into the sandier sediments, increasing the area available for ammonia oxidation to occur, higher concentrations of inhibitory sulphide with pore waters of muddier sediments or a combination of both oxygen and sulphide concentrations. Similar to many other temporal studies of nitrification within estuarine and coastal sediments, decreases in AOB amoA gene abundance were evident during summer and autumn, with maximum abundance and ammonia oxidation rates occurring in winter and early spring. The lack of correlation between AOA amoA gene abundance and ammonium oxidation rate suggests an alternative role for amoA-carrying AOA within these sediments.
2013-08-24 | GSE50163 | GEO
Project description:Effect of drought on ammonia and nitrite oxidisers
Project description:The abundance of bacterial (AOB) and archaeal (AOA) ammonia oxidisers, assessed using quantitative PCR measurements of their respective a-subunit of the ammonia monooxygenase (amoA) genes, and ammonia oxidation rates were measured in four contrasting coastal sediments in the Western English Channel. Sediment was sampled bimonthly from July 2008 to May 2011, and measurements of ammonia oxidiser abundance and activity compared to a range of environmental variables including salinity, temperature, water column nutrients and sediment carbon and nitrogen content. Despite a higher abundance of AOA amoA genes within all sediments, and at all time-points, rates of ammonia oxidation correlated with AOB and not AOA amoA gene abundance. Other than ammonia oxidation rate, sediment particle size was the only variable that correlated with the spatial and temporal patterns of AOB amoA gene abundance, implying a preference of the AOB for larger sediment particles. This is possibly due to deeper oxygen penetration into the sandier sediments, increasing the area available for ammonia oxidation to occur, higher concentrations of inhibitory sulphide with pore waters of muddier sediments or a combination of both oxygen and sulphide concentrations. Similar to many other temporal studies of nitrification within estuarine and coastal sediments, decreases in AOB amoA gene abundance were evident during summer and autumn, with maximum abundance and ammonia oxidation rates occurring in winter and early spring. The lack of correlation between AOA amoA gene abundance and ammonium oxidation rate suggests an alternative role for amoAÂ-carrying AOA within these sediments. Two color array (Cy3 and Cy5): the universal standard 20-mer oligo is printed to the slide with a 70-mer oligo (an archetype). Environmental DNA sequences (fluoresced with Cy3) within 15% of the 70-mer conjugated to a 20-mer oligo (fluoresced with Cy5) complementary to the universal standard will bind to the oligo probes on the array. Signal is the ratio of Cy3 to Cy5. Three replicate probes were printed for each archetype. Two replicate arrays were run on duplicate targets.
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.
Project description:The goal of this study was to measure the effect of heat stress on the transcriptome of a cold-adapted fish species - Trematomus bernacchii - an Antarctic fish species. Keywords: Stress response
Project description:The malate shuttle is traditionally known to maintain the NAD+/NADH balance between the cytosol and mitochondria. Whether the malate shuttle has additional functions was unknown. Here we show that chronic viral infections induced the expression of GOT1, the key enzyme in the malate shuttle, in CD8+ T cells. Got1 deficiency indeed decreased the NAD+/NADH ratio and dampened antiviral CD8+ T cell responses to chronic infection; however, increasing the NAD+/NADH ratio did not restore antiviral T cell responses. Got1 deficiency reduced the production of the ammonia scavenger 2-ketoglutarate and led to toxic ammonia accumulation in CD8+ T cells. Supplementation with 2-ketoglutarate assimilated and detoxified ammonia in Got1-deficient T cells and restored antiviral responses. This study suggests that the major function of the malate shuttle in CD8+ T cells is not to maintain the NAD+/NADH ratio, but rather to detoxify ammonia and enable sustainable ammonia-neutral glutamine catabolism in CD8+ T cells during chronic infections.
Project description:Nitrogen fixation is a highly energy-demanding process and highly regulated at multiple levels. The two major signals that regulate nitrogen fixation in most diazotrophs are oxygen and ammonia. In order to study the complex regulated mechanism and to highlight the complete nitrogen fixing system in genome level, here we present the transcriptional profiles of the nitrogen fixation genes of P.stutzeri A1501 in different growth conditions with a genome-wide DNA microarray. In this study, the three samples of "P.stutzeri A1501 treated with 0.1mM ammonia and 0.5% Oxygen tension","P.stutzeri A1501 treated with 0.1mM ammonia and 0.5% Oxygen tension-2" and "P.stutzeri A1501 treated with 0.1mM ammonia and 0.5% Oxygen tension-3" were three repeat experiments, while, the other three samples of "P.stutzeri A1501 treated with 20mM ammonia and 0.5% Oxygen tension-1", "P.stutzeri A1501 treated with 20mM ammonia and 0.5% Oxygen tension-2" and "P.stutzeri A1501 treated with 20mM ammonia and 0.5% Oxygen tension-3" were three repeat experiments. The gene expressions under these two growth phases were compared to investigate which genes' expression were effected by different ammonia concentrations. Keywords: nitrogen fixation, nitrogen repression
2007-04-20 | GSE6572 | GEO
Project description:Antarctic microorganism genomic study
Project description:Using RNAseq of small RNA libraries isolated from the gill tissue of the Antarctic fish Trematomus bernacchii we have characterized the termal sensitivity of miRNA homologues in these highly stenothermic fish.