Project description:Diatoms perform about 20% of photosynthesis on earth, play a crucial role in forming the base of the marine food web, and sequester anthropogenic carbon into the deep ocean through the biological pump. In some areas of the ocean, diatom growth is limited by the organic micronutrient cobalamin (vitamin B12). Cobalamin affects phytoplankton growth rate and biomass yield, though the consequences of cobalamin limitation are not well understood on the biochemical level. In a controlled laboratory setting, we grew two diatoms, Thalassiosira pseudonana and Navicula pelliculosa, under cobalamin limited and replete conditions to elucidate changes in metabolite pools under cobalamin limitation. Using targeted and untargeted metabolomics, we show that the cobalamin-dependent T. pseudonana experienced a metabolic cascade under cobalamin limitation that a ects the central methionine cycle, the transsulfuration pathway, and the composition of its osmolyte pools. N. pelliculosa, a cobalamin-independent diatom, also showed evidence for changes in the methionine cycle when grown without cobalamin, though to a lesser extent than what we observed in T. pseudonana. In both diatoms the concentration of 5'-methylthioadenosine decreased when limited for cobalamin, suggesting a disruption in the diatoms' polyamine biosynthesis. Furthermore, two acylcarnitines and adenosyl cobalamin accumulated in T. pseudonana under cobalamin limitation, suggesting the use of an adenosylcobalamin-dependent enzyme, methylmalonyl CoA mutase. Overall, these changes in metabolite pools yield insight into the metabolic consequences of cobalamin limitation in diatoms and suggest that cobalamin starvation may have consequences for microbial interactions that are based on metabolite production by phytoplankton. Thalassiosira pseudonana protocols and data are reported in the current study <a href='https://www.ebi.ac.uk/metabolights/MTBLS703' rel='noopener noreferrer' target='_blank'>MTBLS703</a>. Navicula pelliculosa protocols and data are reported in <a href='https://www.ebi.ac.uk/metabolights/MTBLS708' rel='noopener noreferrer' target='_blank'>MTBLS708</a>.

Project description:Diatoms perform about 20% of photosynthesis on earth, play a crucial role in forming the base of the marine food web, and sequester anthropogenic carbon into the deep ocean through the biological pump. In some areas of the ocean, diatom growth is limited by the organic micronutrient cobalamin (vitamin B12). Cobalamin affects phytoplankton growth rate and biomass yield, though the consequences of cobalamin limitation are not well understood on the biochemical level. In a controlled laboratory setting, we grew two diatoms, Thalassiosira pseudonana and Navicula pelliculosa, under cobalamin limited and replete conditions to elucidate changes in metabolite pools under cobalamin limitation. Using targeted and untargeted metabolomics, we show that the cobalamin-dependent T. pseudonana experienced a metabolic cascade under cobalamin limitation that a ects the central methionine cycle, the transsulfuration pathway, and the composition of its osmolyte pools. N. pelliculosa, a cobalamin-independent diatom, also showed evidence for changes in the methionine cycle when grown without cobalamin, though to a lesser extent than what we observed in T. pseudonana. In both diatoms the concentration of 5'-methylthioadenosine decreased when limited for cobalamin, suggesting a disruption in the diatoms' polyamine biosynthesis. Furthermore, two acylcarnitines and adenosyl cobalamin accumulated in T. pseudonana under cobalamin limitation, suggesting the use of an adenosylcobalamin-dependent enzyme, methylmalonyl CoA mutase. Overall, these changes in metabolite pools yield insight into the metabolic consequences of cobalamin limitation in diatoms and suggest that cobalamin starvation may have consequences for microbial interactions that are based on metabolite production by phytoplankton. Navicula pelliculosa protocols and data are reported in the current study <a href='https://www.ebi.ac.uk/metabolights/MTBLS708' rel='noopener noreferrer' target='_blank'>MTBLS708</a>. Thalassiosira pseudonana protocols and data are reported in <a href='https://www.ebi.ac.uk/metabolights/MTBLS703' rel='noopener noreferrer' target='_blank'>MTBLS703</a>.

Project description:Diatoms perform about 20% of photosynthesis on earth, play a crucial role in forming the base of the marine food web, and sequester anthropogenic carbon into the deep ocean through the biological pump. In some areas of the ocean, diatom growth is limited by the organic micronutrient cobalamin (vitamin B12). Cobalamin affects phytoplankton growth rate and biomass yield, though the consequences of cobalamin limitation are not well understood on the biochemical level. In a controlled laboratory setting, we grew two diatoms, Thalassiosira pseudonana and Navicula pelliculosa, under cobalamin limited and replete conditions to elucidate changes in metabolite pools under cobalamin limitation. Using targeted and untargeted metabolomics, we show that the cobalamin-dependent T. pseudonana experienced a metabolic cascade under cobalamin limitation that a ects the central methionine cycle, the transsulfuration pathway, and the composition of its osmolyte pools. N. pelliculosa, a cobalamin-independent diatom, also showed evidence for changes in the methionine cycle when grown without cobalamin, though to a lesser extent than what we observed in T. pseudonana. In both diatoms the concentration of 5'-methylthioadenosine decreased when limited for cobalamin, suggesting a disruption in the diatoms' polyamine biosynthesis. Furthermore, two acylcarnitines and adenosyl cobalamin accumulated in T. pseudonana under cobalamin limitation, suggesting the use of an adenosylcobalamin-dependent enzyme, methylmalonyl CoA mutase. Overall, these changes in metabolite pools yield insight into the metabolic consequences of cobalamin limitation in diatoms and suggest that cobalamin starvation may have consequences for microbial interactions that are based on metabolite production by phytoplankton. Thalassiosira pseudonana protocols and data are reported in the current study <a href='https://www.ebi.ac.uk/metabolights/MTBLS703' rel='noopener noreferrer' target='_blank'>MTBLS703</a>. Navicula pelliculosa protocols and data are reported in <a href='https://www.ebi.ac.uk/metabolights/MTBLS708' rel='noopener noreferrer' target='_blank'>MTBLS708</a>.

Project description:Here, we examined the ramifications of between-species diversity by documenting the transcriptional response of three marine diatoms - Thalassiosira pseudonana, Fragilariopsis cylindrus, and Pseudo-nitzschia multiseries - to the onset of nitrate limitation of growth, a common limiting nutrient in the ocean. Less than 5% of orthologous genes, shared across the three diatoms, displayed the same transcriptional responses across species when growth was limited by nitrate availability. Orthologs, such as those involved in nitrogen uptake and assimilation, as well as carbon metabolism, were differently expressed across the three species. The two pennate diatoms, F. cylindrus and P. multiseries, shared 3,839 clusters without orthologs in the genome of the centric diatom T. pseudonana. A majority of these pennate-clustered genes, as well as the non-orthologous genes in each species, had minimal annotation information, but were often significantly differentially expressed under nitrate limitation, indicating their potential importance in the response to nitrogen availability. Despite these variations in the specific transcriptional response of each diatom, overall transcriptional patterns suggested that all three diatoms displayed a common physiological response to nitrate limitation that consisted of a general reduction in carbon fixation and carbohydrate and fatty acid metabolism and an increase in nitrogen recycling. Transcriptomes were collected for diatom cultures harvested at the onset of stationary phase in low nitrate media (55 M-NM-<M NaNO3, 212 M-NM-<M Na2SiO3, 72.4 M-NM-<M NaH2PO4) or during mid-exponential growth in nutrient-replete media (882 M-NM-<M NaNO3, 106 M-NM-<M Na2SiO3, 36.2 M-NM-<M NaH2PO4) in artificial seawater, maintaining three biological replicates per condition and per diatom (N=18). The SOLiD sequencer (version 4) was used to generate the transcriptomes and the SEAStAR software package was used to process the SOLiD reads and to calculate gene counts. Pooled counts for the nitrate-limited treatment were normalized to pooled counts for the nutrient-replete M-bM-^@M-^\controlM-bM-^@M-^] treatment to generate log fold changes in gene transcription using the R software package edgeR from Bioconductor.

			Action	DRS
	MTBLS708	Other
	FILES	Other
	a_MTBLS708_NEG_HILIC_mass_spectrometry.txt	Txt
	a_MTBLS708_POS_HILIC_mass_spectrometry.txt	Txt
	a_MTBLS708_POS_RP_mass_spectrometry.txt	Txt

Dataset Information

Metabolic consequences of cobalamin scarcity in diatoms as revealed through metabolomics (Navicula pelliculosa study)

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