Project description:Carbon fixation plays a central role in determining cellular redox poise, increasingly understood to be a key parameter in cyanobacterial physiology. In the cyanobacterium Prochlorococcus--—the most abundant phototroph in the oligotrophic oceans--—the carbon-concentrating mechanism (CCM) is reduced to the bare essentials. Given the ability of Prochlorococcus populations to grow under a wide range of oxygen concentrations in the ocean, we wondered how carbon and oxygen physiology intersect in this minimal phototroph. We monitored genome-wide transcription in cells shocked with acute limitation of CO2, O2, or both. O2 limitation produced much smaller transcriptional changes than the broad suppression seen under CO2 limitation and CO2/O2 co-limitation. Strikingly, the transcriptional responses evoked by both CO2 limitation conditions were initially similar to that previously seen in high light stress, but at later timepoints we observed O2-dependent recovery of photosynthesis-related transcripts. These results suggest that oxygen plays a protective role in Prochlorococcus when carbon fixation is not a sufficient sink for light energy.
Project description:Carbon fixation plays a central role in determining cellular redox poise, increasingly understood to be a key parameter in cyanobacterial physiology. In the cyanobacterium Prochlorococcus--—the most abundant phototroph in the oligotrophic oceans--—the carbon-concentrating mechanism (CCM) is reduced to the bare essentials. Given the ability of Prochlorococcus populations to grow under a wide range of oxygen concentrations in the ocean, we wondered how carbon and oxygen physiology intersect in this minimal phototroph. We monitored genome-wide transcription in cells shocked with acute limitation of CO2, O2, or both. O2 limitation produced much smaller transcriptional changes than the broad suppression seen under CO2 limitation and CO2/O2 co-limitation. Strikingly, the transcriptional responses evoked by both CO2 limitation conditions were initially similar to that previously seen in high light stress, but at later timepoints we observed O2-dependent recovery of photosynthesis-related transcripts. These results suggest that oxygen plays a protective role in Prochlorococcus when carbon fixation is not a sufficient sink for light energy. Two biological replicates of timecourses under four conditions: medium bubbled with air (control) or three experimental gases (low CO2; low O2; or low CO2 and low O2)
Project description:Analysis of microbial gene expression in response to physical and chemical gradients forming in the Columbia River, estuary, plume and coastal ocean was done in the context of the environmental data base. Gene expression was analyzed for 2,234 individual genes that were selected from fully sequenced genomes of 246 prokaryotic species (bacteria and archaea) as related to the nitrogen metabolism and carbon fixation. Seasonal molecular portraits of differential gene expression in prokaryotic communities during river-to-ocean transition were created using freshwater baseline samples (268, 270, 347, 002, 006, 207, 212).
Project description:Cyanidioschyzon merolae (C. merolae) is an acidophilic red alga growing in a naturally low carbon dioxide (CO2) environment. Although it uses a ribulose 1,5-bisphosphate carboxylase/oxygenase with high affinity for CO2, the survival of C. merolae relies on functional photorespiratory metabolism. In this study, we quantified the transcriptomic response of C. merolae to changes in CO2 conditions. We found distinct changes upon shifts between CO2 conditions, such as a concerted up-regulation of photorespiratory genes and responses to carbon starvation. We used the transcriptome data set to explore a hypothetical CO2 concentrating mechanism in C. merolae, based on the assumption that photorespiratory genes and possible candidate genes involved in a CO2 concentrating mechanism are co-expressed. A putative bicarbonate transport protein and two α-carbonic anhydrases were identified, which showed enhanced transcript levels under reduced CO2 conditions. Genes encoding enzymes of a PEP-CK-type C4 pathway were co-regulated with the photorespiratory gene cluster. We propose a model of a hypothetical low CO2 compensation mechanism in C. merolae integrating these low CO2-inducible components.
Project description:We performed RNA-sequencing experiments to examine the differential regulation of genes in the genome of the Southern Ocean diatom Fragilariopsis cylindrus including diverged alleles. RNA-seq was performed on three replicate samples for each experimental condition. Phytoplankton cells were grown under six different experimental conditions including (1) optimal growth, (2) freezing temperatures, (3) elevated temperature, (4) elevated carbon dioxide concentrations, (5) low iron concentrations and (6) prolonged darkness. Total RNA was extracted using a guanidinium thiocyanate-phenol-chloroform extraction protocol, followed by DNase I treatment and RNA purification (Quiagen). First strand cDNA synthesis was performed using random hexamers. Library preparation was performed using the RNA-seq Sample Prep Kit (Illumina) and sequencing was conducted according to the TruSeq RNA sequencing protocol (Illumina) All samples were sequenced together in one flowcell on one lane.
Project description:The Antarctic krill provides central ecosystems services to the Southern Ocean grazing on autotroph and heterotoph diet and constituting the dominant food source for higher trophic levels. Moreover, E. superba's extensive equipment with biomacromolecule hydrolysing enzymes represents a largely untapped resource for applied purposes. The proteome compendium of krill provides a valuable basis for future studies on krill biology (e.g., metabolism, development, migration behaviour), for krill's contribution to organic matter turnover in the Southern Ocean, as well as for multilevel biotechnological prospecting.
Project description:The Antarctic krill provides central ecosystems services to the Southern Ocean grazing on autotroph and heterotoph diet and constituting the dominant food source for higher trophic levels. Moreover, E. superba's extensive equipment with biomacromolecule hydrolysing enzymes represents a largely untapped resource for applied purposes. The proteome compendium of krill provides a valuable basis for future studies on krill biology (e.g., metabolism, development, migration behaviour), for krill's contribution to organic matter turnover in the Southern Ocean, as well as for multilevel biotechnological prospecting.
Project description:The Antarctic krill provides central ecosystems services to the Southern Ocean grazing on autotroph and heterotoph diet and constituting the dominant food source for higher trophic levels. Moreover, E. superba's extensive equipment with biomacromolecule hydrolysing enzymes represents a largely untapped resource for applied purposes. The proteome compendium of krill provides a valuable basis for future studies on krill biology (e.g., metabolism, development, migration behaviour), for krill's contribution to organic matter turnover in the Southern Ocean, as well as for multilevel biotechnological prospecting.
Project description:The Antarctic krill provides central ecosystems services to the Southern Ocean grazing on autotroph and heterotoph diet and constituting the dominant food source for higher trophic levels. Moreover, E. superba's extensive equipment with biomacromolecule hydrolysing enzymes represents a largely untapped resource for applied purposes. The proteome compendium of krill provides a valuable basis for future studies on krill biology (e.g., metabolism, development, migration behaviour), for krill's contribution to organic matter turnover in the Southern Ocean, as well as for multilevel biotechnological prospecting.