Project description:We investigated the functional gene expression changes associated with temperature stress in two psychrophilic sea ice bacteria, Polaribacter sp. ALD9 and Shewanella sp. ALD11.
Project description:Proteorhodopsin has been an ongoing hot topic for the past decade. However the complete physiological role of this extremely widely distributed protein remains mysterious. In this study we aim to give an insight to the physiology of a proteorhodopsin-containing sea ice bacteria – Psychroflexus torquis using gel-free label-free proteomic approach for the first time. We also addressed the life strategy that used by this organism to successfully inhabit extreme sea ice environment.
Project description:Sulfur metabolism in the deep-sea cold seep has been mentioned to have an important contribution to the biogeochemical cycle of sulfur in previous studies. And sulfate reducing bacteria have also been considered to be a dominant microbial population in the deep-sea cold seep and play a crucial role in this process. However, most of sulfate reducing bacteria from cold seep still cannot be purely cultured under laboratory conditions, therefore the actual sulfur metabolism pathways in sulfate reducing bacteria from the deep-sea cold seep have remained unclear. Here, we isolate and pure culture a typical sulfate reducing bacterium Desulfovibrio marinus CS1 from the sediment sample of the deep-sea cold seep in the South China Sea, which provides a probability to understand the sulfur metabolism in the cold seep.
Project description:The sea-ice dwelling diatom Fragilariopsis Cylindrus was cultured for 4 months under dark or light exposed conditions to mimic the effects of Antarctic winter growth conditions. Cells were harvested periodically and LFQ proteomics used to investigate the molecular mechanisms of dark survival.
Project description:The deep-sea tubeworm Riftia pachyptila is a model system for a mutualistic association: The adult worm has no digestive system, but completely relies on one phylotype of endosymbiotic chemosynthetic bacteria for nutrition. The bacteria, in turn, are provisioned by the host. Metabolism and physiology of this symbiosis, particularly of the uncultured symbiont, have been subject to various studies. Yet, how both partners interact on the molecular level remains largely unknown. To study these host-symbiont interactions in detail, we sequenced the R. pachyptila host transcriptome de novo, and conducted comprehensive metaproteomic comparisons of symbiont-containing and symbiont-free R. pachyptila tissues under energy-rich and energy-limiting conditions. Our results demonstrate that R. pachyptila invests a considerable part of its proteome to provision the symbionts with inorganic compounds. It acquires symbiont-derived biomass primarily by digesting parts of the symbiont population. The R. pachyptila immune system apparently not only protects the holobiont from pathogens, but is also involved in symbiont population control. The symbiont expresses a repertoire of proteins dedicated to communication with the host, including eukaryote-like proteins that may counteract phagocytosis. During energy limitation, i.e., when reduced sulfur compounds are lacking, the host apparently increases symbiont digestion. We show here an intricate network of interaction pathways that shapes the R. pachyptila holobiont. Together with the metabolic flexibility of the association under varying energy conditions, this probably forms the basis for the success of this tight association under the highly challenging deep-sea conditions.
Project description:Colonization of deep-sea hydrothermal vents by invertebrates was made efficient through their adaptation to a symbiotic lifestyle with chemosynthetic bacteria, the primary producers of these ecosystems. Anatomical adaptations such as the establishment of specialized cells or organs have been evidenced in numerous deep-sea invertebrates. However, very few studies detailed global inter-dependencies between host and symbionts in these ecosystems. In this study, we proposed to describe, using a proteo-transcriptomic approach, the effects of symbionts on the deep-sea mussel Bathymodiolus azoricus’ molecular biology. We induced an in situ depletion of symbionts and compared the proteo-transcriptome of the gills of mussels in three conditions: symbiotic mussels (natural population), symbiont-depleted mussels and aposymbiotic mussels
Project description:We sampled the microbial community at the sea ice edge in McMurdo Sound, Ross Sea at the same location (-77.62S, 165.41E) for four weeks (as described in Wu et al 2019, Nat. Comms.). We had four sampling dates corresponding to weeks 1 to 4: December 28 2014, January 6, 15, and 22 2015. Large volumes of water (150--250 L) were filtered from 1 m depth at the sea ice edge, and passed through three filters sequentially (3.0, 0.8, and 0.1 um, each 293 mm Supor filters). Filters with collected biomass were then placed in tubes with a sucrose-based preservative buffer (20 mM EDTA, 400 mM NaCl, 0.75 M sucrose, 50 mM Tris-HCl, pH 8.0) and stored at -80 C until sample processing. We extracted proteins after buffer exchange into a 3\% SDS solution as previously described Wu et al 2019, Nat. Comms.
Project description:Sea-ice algae provide an important source of primary production in polar regions, yet we have limited understanding of their responses to the seasonal cycling of temperature and salinity. Using a targeted liquid chromatography-mass spectrometry-based metabolomics approach, we found that axenic cultures of the Antarctic sea-ice diatom, Nitzschia lecointei, displayed large differences in their metabolomes when grown in a matrix of conditions that included temperatures of –1 and 4°C, and salinities of 32 and 41, despite relatively small changes in growth rate. Temperature exerted a greater effect than salinity on cellular metabolite pool sizes, though the N- or S-containing compatible solutes, 2,3-dihydroxypropane-1-sulfonate (DHPS), glycine betaine (GBT), dimethylsulfoniopropionate (DMSP), and proline responded strongly to both temperature and salinity, suggesting complexity in their control. We saw the largest (> 4 fold) response to salinity for proline. DHPS, a rarely studied but potential compatible solute, reached the highest intracellular compatible solute concentrations of ~ 85 mM. When comparing the culture findings to natural Arctic sea-ice diatom communities, we found extensive overlap in metabolite profiles, highlighting the relevance of culture-based studies to probe environmental questions. Large changes in sea-ice diatom metabolomes and compatible solutes over a seasonal cycle could be significant components of biogeochemical cycling within sea ice.