Project description:Our paper presents the results of a study in which we used whole genome bisulfite sequencing (WGBS), RNA-Seq (i.e. transcriptomics), high-CO2 physiology experiments, and spatiotemporally separated samples isolated in situ (i.e. directly from the ocean) to examine the metabolic potential of genome-wide cytosine (5mC) methylation (i.e. epigenomics), its potential impacts to transcriptional dynamics under both present-day and future ocean acidification conditions, and its biogeographic conservation in the globally-significant, biogeochemically-critical marine cyanobacterium Trichodesmium.
Project description:Our paper presents the results of a study in which we used whole genome bisulfite sequencing (WGBS), RNA-Seq (i.e. transcriptomics), high-CO2 physiology experiments, and spatiotemporally separated samples isolated in situ (i.e. directly from the ocean) to examine the metabolic potential of genome-wide cytosine (5mC) methylation (i.e. epigenomics), its potential impacts to transcriptional dynamics under both present-day and future ocean acidification conditions, and its biogeographic conservation in the globally-significant, biogeochemically-critical marine cyanobacterium Trichodesmium.
Project description:Biogeographic conservation and CO2-dynamics of the cytosine methylome in the globally important cyanobacterium Trichodesmium [WGBS]
Project description:A major challenge in modern biology is understanding how the effects of short-term biological responses influence long-term evolutionary adaptation, defined as a genetically determined increase in fitness to novel environments. This is particularly important in globally important microbes experiencing rapid global change, due to their influence on food webs, biogeochemical cycles, and climate. Epigenetic modifications like methylation have been demonstrated to influence short-term plastic responses, which ultimately impact long-term adaptive responses to environmental change. However, there remains a paucity of empirical research examining long-term methylation dynamics during environmental adaptation in nonmodel, ecologically important microbes. Here, we show the first empirical evidence in a marine prokaryote for long-term m5C methylome modifications correlated with phenotypic adaptation to CO2, using a 7-year evolution experiment (1,000+ generations) with the biogeochemically important marine cyanobacterium Trichodesmium. We identify m5C methylated sites that rapidly changed in response to high (750 µatm) CO2 exposure and were maintained for at least 4.5 years of CO2 selection. After 7 years of CO2 selection, however, m5C methylation levels that initially responded to high-CO2 returned to ancestral, ambient CO2 levels. Concurrently, high-CO2 adapted growth and N2 fixation rates remained significantly higher than those of ambient CO2 adapted cell lines irrespective of CO2 concentration, a trend consistent with genetic assimilation theory. These data demonstrate the maintenance of CO2-responsive m5C methylation for 4.5 years alongside phenotypic adaptation before returning to ancestral methylation levels. These observations in a globally distributed marine prokaryote provide critical evolutionary insights into biogeochemically important traits under global change.
Project description:Our paper presents the results of a study in which we used whole genome bisulfite sequencing (WGBS) and RNA-Seq (i.e. transcriptomics) to examine the long-term epigenomic dynamics of an experimenta evolution study under high CO2 in the marine cyanobacterium Trichodesmium. We identify m5C methylated sites that rapidly change in response to short-term high CO2 exposure, which are then maintained for 4.5 years even after adaptation (i.e. trait canalization). After 7 years of CO2 selection, high-CO2 triggered methylation levels return to ancestral, low-CO2 levels, consistent with genetic assimilation theory and observations in eukaryotic model systems. These data suggest a potential role for m5C methylation in prokaryotic trait canalization and identify genetic assimilation as an evolutionary mechanism of potential biogeochemical importance under global change factors.
Project description:Our paper presents the results of a study in which we used whole genome bisulfite sequencing (WGBS) and RNA-Seq (i.e. transcriptomics) to examine the long-term epigenomic dynamics of an experimenta evolution study under high CO2 in the marine cyanobacterium Trichodesmium. We identify m5C methylated sites that rapidly change in response to short-term high CO2 exposure, which are then maintained for 4.5 years even after adaptation (i.e. trait canalization). After 7 years of CO2 selection, high-CO2 triggered methylation levels return to ancestral, low-CO2 levels, consistent with genetic assimilation theory and observations in eukaryotic model systems. These data suggest a potential role for m5C methylation in prokaryotic trait canalization and identify genetic assimilation as an evolutionary mechanism of potential biogeochemical importance under global change factors.
Project description:The oceanic N2-fixing cyanobacterium Trichodesmium spp. form extensive surface blooms and contribute significantly to marine carbon and nitrogen cycles in the oligotrophic subtropical and tropical oceans. Trichodesmium grows in salinities from 27 to 43 parts per thousand (ppt), yet its salt acclimation strategy remains enigmatic because the genome of Trichodesmium erythraeum strain IMS101 lacks all genes for the biosynthesis of any known compatible solute. Using NMR and liquid chromatography coupled to mass spectroscopy, we identified the main compatible solute in T. erythraeum strain IMS101 as the quaternary ammonium compound N,N,N-trimethyl homoserine (or homoserine betaine) and elucidated its biosynthetic pathway. The identification of this compatible solute explains how Trichodesmium spp. can thrive in the marine system at varying salinities and provides further insight into the diversity of microbial salt acclimation.
Project description:The marine cyanobacterium Trichodesmium sp. accounts for approximately half of the annual 'new' nitrogen introduced to the global ocean but its biogeography and activity is often limited by the availability of iron (Fe). A major source of Fe to the open ocean is Aeolian dust deposition in which Fe is largely comprised of particles with reduced bioavailability over soluble forms of Fe. We report that Trichodesmium erythraeum IMS101 has improved growth rate and photosynthetic physiology and down-regulates Fe-stress biomarker genes when cells are grown in the direct vicinity of, rather than physically separated from, Saharan dust particles as the sole source of Fe. These findings suggest that availability of non-soluble forms of dust-associated Fe may depend on cell contact. Transcriptomic analysis further reveals unique profiles of gene expression in all tested conditions, implying that Trichodesmium has distinct molecular signatures related to acquisition of Fe from different sources. Trichodesmium thus appears to be capable of employing specific mechanisms to access Fe from complex sources in oceanic systems, helping to explain its role as a key microbe in global biogeochemical cycles.