Project description:Thylakoid membrane preparations active in photosynthetic electron transport have been obtained from two marine red algae, Griffithsia monilis and Anotrichium tenue. High concentrations (0.5-1.0 M) of salts such as phosphate, citrate, succinate and tartrate stabilized functional binding of phycobilisomes to the membrane and also stabilized Photosystem II-catalysed electron-transport activity. High concentrations (1.0 M) of chloride and nitrate, or 30 mM-Tricine/NaOH buffer (pH 7.2) in the absence of salts, detached phycobilisomes and inhibited electron transport through Photosystem II. The O2-evolving system was identified as the electron-transport chain component that was inhibited under these conditions. Washing membranes with buffers containing 1.0-1.5 M-sorbitol and 5-50 mM concentrations of various salts removed the outer part of the phycobilisome but retained 30-70% of the allophycocyanin 'core' of the phycobilisome. These preparations were 30-70% active in O2 evolution compared with unwashed membranes. In the sensitivity of their O2-evolving apparatus to the composition of the medium in vitro, the red algae resembled blue-green algae and differed from other eukaryotic algae and higher plants. It is suggested that an environment of structured water may be essential for the functional integrity of Photosystem II in biliprotein-containing algae.
Project description:The study of macroalgae capacity to acclimate and recover in environments contaminated with Cu and Cd could prove a promising way to understand the tolerance mechanisms of these seaweeds against different pollutants. This study used as a model organism Gracilaria tenuistipitata (Rhodophyta), a macroalga with economic and ecological importance. The partial transcriptome of G. tenuistipitata was profiled using cDNA microarrays in the sixth day of exposition to EC50 metals. Genes involved in Cu and Cd chronic stress belonging to various functional categories suffered shallow modifications. This possibly indicates that G. tenuistipitata would be in the acclimatization process. In addition, the expression of nine stress genes accompanied by analysis of the photosynthetic rate of seaweed to both metals in three different time frames was analyzed. Genetic variation linked to the mechanism of resistance of the algae, determined from EC50 culture conditions established for two metals, occurred in the early hours of treatment. It was found that G. tenuistipitata was able to accumulate these two metals and to resist and acclimate to the negative effects produced by these elements. The temporal analysis from the nine specific genes showed some specific transcriptional responses of the G. tenuistipitata, exposed to Cu and Cd.
Project description:The study of macroalgae capacity to acclimate and recover in environments contaminated with Cu and Cd could prove a promising way to understand the tolerance mechanisms of these seaweeds against different pollutants. This study used as a model organism Gracilaria tenuistipitata (Rhodophyta), a macroalga with economic and ecological importance. The partial transcriptome of G. tenuistipitata was profiled using cDNA microarrays in the sixth day of exposition to EC50 metals. Genes involved in Cu and Cd chronic stress belonging to various functional categories suffered shallow modifications. This possibly indicates that G. tenuistipitata would be in the acclimatization process. In addition, the expression of nine stress genes accompanied by analysis of the photosynthetic rate of seaweed to both metals in three different time frames was analyzed. Genetic variation linked to the mechanism of resistance of the algae, determined from EC50 culture conditions established for two metals, occurred in the early hours of treatment. It was found that G. tenuistipitata was able to accumulate these two metals and to resist and acclimate to the negative effects produced by these elements. The temporal analysis from the nine specific genes showed some specific transcriptional responses of the G. tenuistipitata, exposed to Cu and Cd. Three-condition experiment, control cells cultivated in seawater enriched with von Stosch solution vs. copper and cadmium (indepedent) treated cells. Biological replicates: 4 control, 2 copper treated, 2 cadmium treated. All independently grown and harvested. Four replicates per array.
Project description:Colonization of land from marine environments was a major transition for biological life on Earth, and intertidal adaptation was a key evolutionary event in the transition from marine- to land-based lifestyles. Multicellular intertidal red algae exhibit the earliest, systematic, and successful adaptation to intertidal environments, with Porphyra sensu lato (Bangiales, Rhodophyta) being a typical example. We used proteomic analyse to reveal the complex regulation of rapid responses to intertidal dehydration/rehydration cycling within Neoporphyra haitanensis. These adaptations include rapid regulation of its photosynthetic system, a readily available capacity to utilize ribosomal stores, an excess of methylation supply to rapidly synthesize proteins, and a strong anti-oxidation system to dissipate excess redox energy upon exposure to air. These novel insights into the unique adaptations of red algae to intertidal lifestyles inform our understanding of adaptations to intertidal ecosystems and the unique evolutionary steps required for intertidal colonization by biological life.
Project description:We investigated light dependent gene expression changes in the marine ochrophyte Nannochloropsis oceanica CCMP1779. These algae have several putative blue light photoreceptors but appear to lack red light photoreceptors. To study early light signaling in N. oceanica and avoid as much as possible secondary downstream events, we quantified gene expression changes in dark-adapted cells after a short blue or red light pulse. More genes were differentially expressed under blue than under red light. In addition, fold change in expression was smaller for the red light-treated samples. For example, the median fold change of induced genes was 3 for blue light and 2.5 for red light. Moreover, hierarchical cluster analysis showed that gene expression after red light treatment was more similar to the dark control than after blue light treatment.
Project description:Marine brown algae produce the highly recalcitrant polysaccharide fucoidan, contributing to long-term oceanic carbon storage and climate regulation. Fucoidan is degraded by specialized heterotrophic bacteria, which promote ecosystem function and global carbon turnover using largely uncharacterized mechanisms. Here, we isolate and study two Planctomycetota strains from the microbiome associated with the alga Fucus spiralis, which grow efficiently on chemically diverse fucoidans. One of the strains appears to internalize the polymer, while the other strain degrades it extracellularly. Multi-omic approaches show that fucoidan breakdown is mediated by the expression of divergent polysaccharide utilization loci, and endo-fucanases of family GH168 are strongly upregulated during fucoidan digestion. Enzymatic assays and structural biology studies reveal how GH168 endo-fucanases degrade various fucoidan cores from brown algae, assisted by auxiliary hydrolytic enzymes. Overall, our results provide insights into fucoidan processing mechanisms in macroalgal-associated bacteria.
Project description:We have studied the transcriptional, metabolic and photo-physiological responses to light of different spectral quality in the marine diatom Phaeodactylum tricornutum through time-series studies of cultures exposed to equal doses of photosynthetically usable radiation of blue, green and red light. The experiments showed that short-term differences in gene expression and profiles are mainly light quality-dependent. Transcription of photosynthesis-associated nuclear genes was activated mainly through a light quality-independent mechanism likely to rely on chloroplast-to-nucleus signaling. In contrast, genes encoding proteins important for photoprotection and PSII repair were highly dependent on a blue light receptor-mediated signal. Changes in energy transfer efficiency by light-harvesting pigments were spectrally dependent; furthermore, a declining trend in photosynthetic efficiency was observed in red light. The combined results suggest that diatoms possess a light quality-dependent ability to activate photoprotection and efficient repair of photodamaged PSII. In spite of approximately equal numbers of PSII-absorbed quanta in blue, green and red light, the spectral quality of light is important for diatom responses to ambient light conditions. Continuous, axenic culturing of P. tricornutum was done as described in Nymark et al. (2009). The cultures were incubated at 15M-BM-0C under cool white fluorescent light (Philips TLD 36W/96) providing a scalar irradiance (EPAR) of 100 M-NM-<mol m-2 s-1 under continuous white light (CWL) conditions. Upon the onset of the experiment the cultures were synchronized by 48 h dark-treatment (D48). Thereafter the algae were exposed to blue light (BL), green light (GL) or red light (RL) provided by a waveband specific LED panel (SL3500, Photon Systems Instruments). The algae were exposed to 0.5 h, 6 h or 24 h of: 1) 230 M-NM-<mol m-2 s-1 of RL, 2) 100 M-NM-<mol m-2 s-1 of GL, 3) 50 M-NM-<mol m-2 s-1 of BL or 4) 100 M-NM-<mol m-2 s-1 of WL respectively. Three biological replicas for each of the treatments were harvested. Data for the white light exposure and 48h dark treatment is described in GSE42039, PMID: 23520530.
Project description:About one half of the global, biogenic carbon dioxide fixation into organic matter is driven by microscopic algae in the surface oceans. These microalgal activities generate, among other molecules, polysaccharides that are food for and recycled by bacteria with polysaccharide utilization loci (PULs). These genetic clusters of co-evolved genes, which work together in recognition, depolymerizing and uptake of one type of polysaccharide. However, we rarely know the substrates of PULs present in marine bacteria. Here we investigated the proteomic and physiological response of mannan PULs from marine Flavobacteriia isolated in the North Sea. The genomic clusters of these marine Bacteroidetes are related to PULs of human gut Bacteroides strains, which are known to digest α- and β-mannans from yeasts and plants respectively. Proteomics and defined growth experiments with these types of mannans as sole carbon source confirmed the functional prediction. Our data suggest that biochemical principles established for gut or terrestrial microbes apply to marine bacteria even though the PULs are evolutionary distant. Moreover, our data support discoveries from the 60th reporting mannans in microalgae suggesting that these polysaccharides play an important role in the marine carbon cycle.