ABSTRACT: Photosynthetic, respirational and growth response of six benthic diatoms from the Antarctic Peninsula as function of salinity and temperature variations
Project description:In estuaries and coastal areas, salinity regimes vary with river discharge, seawater evaporation, morphology of the coastal waterways, and dynamics of marine water mixing. Therefore, microalgae have to respond to salinity variations at various time scales, from daily to annual cycling. They might also adapt to physical alteration that might induce loss of connectivity and enclosure of water bodies. Here we integrate physiological-based assays, morphological plasticity with functional genomics approach to examine the regulatory change that occur during the acclimation to salinity in an estuary diatom, Thalassiosira weissflogii. We found that this diatom respond to salinity (i.e. 21, 28 and 35 psu) with minute adjustments of its physiology (i.e., carbon and silicon metabolisms, pigments concentration and photosynthetic parameters). In contrast after short- (~ 5 generations) or long-term (~ 700 generations) culture at the different salinity we found a large transcriptome reprogramming. With most of the genes being down-regulated in long-term, and only a few genes in common between short and long term experiments.
2018-10-02 | GSE73987 | GEO
Project description:DNA Metabarcoding of Antarctic benthic diatoms
Project description:Divergent functions of two clades of flavodoxin in diatoms mitigate oxidative stress and iron limitation Thalassiosira pseudonana and 4 open-ocean diatoms were subjected to iron limitation or short-term oxidative stress (hydrogen peroxide). mRNA profiles of T. pseudonana (CCMP1335), Thalassiosira oceanica (CCMP1005), Amphora coffeaeformis (CCMP1405), Chaetoceros sp. (CCMP199), and Cylindrotheca closterium (CCMP340).
Project description:According to the present theories, in nutrient-repleted conditions diatoms should not be affected by turbulence. We made laboratory experiments to demonstrate that two chain forming diatoms sense and respond to turbulence by varying their chain length spectra and tuning their metabolism. We compared transcriptomes of turbulence-exposed cells with still conditions and analyzed the effects.
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.
