Project description:Microbial eukaryote community structure during early phytoplankton blooms in the naturally iron-fertilized Kerguelen area (Southern Ocean) Targeted Locus (Loci)
Project description:Iron and light are typically recognized as major limiting factors controlling phytoplankton growth in the Southern Ocean. Recent field-based evidence suggests, however, that manganese concentrations in this region can be low enough to impact phytoplankton physiology and primary productivity. Our study examined the interactive influence of combined iron and manganese deprivation on protein expression and photophysiology in Phaeocystis antarctica, a key Antarctic phytoplankter, and provide taxon-specific proteomic evidence that natural Southern Ocean Phaeocystis populations regularly experience stress due to combined low manganese and iron availability. In culture, combined low iron and manganese induced large scale changes in the Phaeocystis proteome and resulted in reorganization of key components of the photosynthetic apparatus; these differences were largely distinct from those arising from changes in irradiance. These results implicate manganese availability as an important driver of Southern Ocean productivity and demonstrate the utility of peptide mass spectrometry as a tool for mapping of manganese contributions to HNLC conditions in this region.
Project description:Samples were taken from surface, 150m and 350m depth in HNLS waters and waters off the coast of Kerguelen Island in the Indian sector of the Southern Ocean during the Mobydick cruise in Feb/March 2018. Environmental samples were taken and filtered according to protocol. Using SDS page proteins were extracted and purified. For proteomic analysis, technical replicates (derived from two separate MS/MS runs) were combined.
Project description:Samples were taken from surface, 150m and 350m depth in HNLS waters and waters off the coast of Kerguelen Island in the Indian sector of the Southern Ocean during the Soclim cruise in November 2016. Environmental samples were taken and filtered according to protocol. Using SDS page proteins were extracted and purified. For proteomic analysis, technical replicates (derived from two separate MS/MS runs) were combined.
Project description:Samples were taken from surface, 150m and 350m depth in HNLS waters and waters off the coast of Kerguelen Island in the Indian sector of the Southern Ocean during the Mobydick cruise in Feb/March 2018. Environmental samples were taken and filtered according to protocol. Using SDS page proteins were extracted and purified. For proteomic analysis, technical replicates (derived from two separate MS/MS runs) were combined.
Project description:Fragilariopsis cylindrus is an abundant diatom species in the Southern Ocean, where low iron and manganese availability constrain microbial growth and biogeochemical cycles. The molecular mechanisms used by polar diatoms including F. cylindrus to cope with trace metal limitations remain largely unexplored. Here we present phenotypic characterizations and high resolution proteomics profiles of F. cylindrus grown under controlled iron (low, medium, high) and manganese (low, high) conditions that reflect those observed in the Southern Ocean. Using data-independent acquisition mass spectrometry, we quantified over 8,000 unique proteins with high reproducibility. We captured diverse metabolic responses related to photosynthesis, elemental transport and intracellular trafficking, and protein synthesis. We show that several canonical iron stress response proteins (e.g., phytotransferrin) are consistently identified under low iron conditions, and identify additional useful iron and manganese stress biomarkers that could be explored in field measurements. Our data also support the notion that one flavodoxin copy in F. cylindrus is iron responsive and one is not. This dataset is a valuable resource for understanding trace metal physiology in polar diatoms, and provides a way for connecting molecular responses with expressed phenotypes and biogeochemical activity in the ocean.
Project description:We conducted two iron-temperature bioassay incubation experiments during the austral summer of 2018-2019 in the Weddell Sea, Southern Ocean. The first bioassay (BA1) was initiated on December 28th, 2018, approximately 560 km away from the ice edge at 65°S 0.038°E. The second bioassay (BA2) was initiated on January 9th, 2019, approximately 70 km from the ice edge at 70.15°S 11.02°W (Figure 1A). For both bioassays, we collected sea water at 20 m depth using a custom-built ultraclean CTD sampling system – “Titan” (De Baar et al. 2008). We chose this depth to minimize light shock when the microbial community was brought on deck, and to prevent trace metal contamination from the ship. After recovery, Titan was moved into a dedicated, temperature-controlled, trace-metal-clean (TMC) laboratory container where the sea water was used for initial (T0) sampling, and to fill triplicate, 20 L, TMC cubitainers for each iron-temperature treatment. The treatment matrix including four iron-temperature conditions: low iron – low temperature, high iron – low temperature, low iron – high temperature, high iron – high temperature. We did not add any iron to the low iron treatments. We supplemented the high iron treatments with a naturally occurring but rare isotope of 57Fe, which allowed us to differentiate between the added iron and iron already present in the water (mainly 56Fe). For this, we made a 40 µM 57FeCl3 stock solution in 0.1 M trace-metal grade HCl, then added 1 mL of this stock to each of the high iron cubitainers. This resulted in an initial dissolved 57Fe concentration of 2 nM in the high iron treatments. We then sealed the cubitainers and placed them inside temperature-controlled deck incubators where the low temperature treatments were incubated under in situ temperature, and the high temperature treatments were incubated under in situ + 2 °C (Table S1).
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.