Project description:We isolate the cultivable microbiome of a diatom and show that different bacteria have commensal, antagonistic, or synergistic effects on the diatom. One synergistic bacterium enhances growth of the diatom by production of auxin, a phytohormone. The diatom and its synergistic bacterium appear to use auxin and tryptophan as signaling molecules that drive nutrient exchange. Detection of auxin molecules and biosynthesis gene transcripts in the Pacific Ocean suggests that these interactions are widespread in marine ecosystems.
Project description:T. pseudonana tiling arrays were used to validate gene models and to predict new genes in the genome of this diatom. The tiling array data validated transcription of about 41% (4,653) of the 11,390 computationally predicted genes. An additional 1,132 transcripts were identified that did not correspond to modeled genes with few of these transcripts (<17%) predicted to encode proteins with homology (e-value < 10-05) to publicly available proteins. These newly identified transcripts have an average length of 1,549 bp, comparable to the average length of the computationally derived genes. Whole genome tiling arrays were conducted under silicon replete and deplete growth conditions to identify new genes involved in the synthesis of the diatom silica cell wall. We analyzed 2 sets of arrays (8 arrays each): one from growth under silicon replete and another one from growth under silicon deplete conditions.
Project description:Phytoplankton and bacteria form the base of marine ecosystems and their interactions drive global biogeochemical cycles. The effect of bacteria and bacteria-produced compounds on diatoms range from synergistic to pathogenic and can affect the physiology and transcriptional patterns of the interacting diatom. Here, we investigate physiological and transcriptional changes in the marine diatom Thalassiosira pseudonana induced by extracellular metabolites of a known antagonistic bacterium Croceibacter atlanticus. Mono-cultures of C. atlanticus released compounds that inhibited diatom cell division and elicited a distinctive phenotype of enlarged cells with multiple plastids and nuclei, similar to what was observed when the diatom was co-cultured with the live bacteria. The extracellular C. atlanticus metabolites induced transcriptional changes in diatom pathways that include recognition and signaling pathways, cell cycle regulation, carbohydrate and amino acid production, as well as cell wall stability. Phenotypic analysis showed a disruption in the diatom cell cycle progression and an increase in both intra- and extracellular carbohydrates in diatom cultures after bacterial exudate treatment. The transcriptional changes and corresponding phenotypes suggest that extracellular bacterial metabolites, produced independently of direct bacterial-diatom interaction, may modulate diatom metabolism in ways that support bacterial growth.
Project description:To identify the molecular components involved in diatom cell division, global transcript level changes were monitored over the silicon-synchronized cell cycle the model diatom Thalassiosira pseudonana.
Project description:T. pseudonana tiling arrays were used to validate gene models and to predict new genes in the genome of this diatom. The tiling array data validated transcription of about 41% (4,653) of the 11,390 computationally predicted genes. An additional 1,132 transcripts were identified that did not correspond to modeled genes with few of these transcripts (<17%) predicted to encode proteins with homology (e-value < 10-05) to publicly available proteins. These newly identified transcripts have an average length of 1,549 bp, comparable to the average length of the computationally derived genes. Whole genome tiling arrays were conducted under silicon replete and deplete growth conditions to identify new genes involved in the synthesis of the diatom silica cell wall. Keywords: silicon, stress response, cell wall
Project description:Extensive gene methylation correlated strongly with transcriptional silencing and differential expression under specific conditions. DNA methylation and its role in gene regulation is conserved in stramenopile. Methylome of the whole genome of diatom phaeodactylum tricornutum.
Project description:Diatoms, which are responsible for up to 40% of the 45 to 50 billion metric tons of organic carbon production each year in the sea, are particularly sensitive to Fe stress. Here we describe the transcriptional response of the pennate diatom Phaeodactylum tricornutum to Fe limitation using a partial genome microarray based on EST and genome sequence data. Processes carried out by components rich in Fe, such as photosynthesis, mitochondrial electron transport and nitrate assimilation are down-regulated to cope with the reduced cellular iron quota. This retrenchment is compensated by nitrogen (N) and carbon (C) reallocation from protein and storage carbohydrate degradation, adaptations to chlorophyll biosynthesis and pigment metabolism, removal of excess electron s by mitochondrial alternative oxidase (AOX), augmented Fe-independent oxidative stress responses, and sensitized iron capture mechanisms. Keywords: Marine phytoplankton, pinnate diatom
Project description:Diatoms, which are important planktons widespread in various aquatic environments, are believed to play a vital role in primary production as well as silica cycling. The genomes of the pennate diatom Phaeodactylum tricornutum and the centric diatom Thalassiosira pseudonana have been sequenced, revealing some characteristics of the diatomsâ mosaic genome as well as some features of their fatty acid metabolism and urea cycle, and indicating their unusual properties. To identify microRNAs (miRNAs) from P. tricornutum and to study their probable roles in nitrogen and silicon metabolism, we constructed and sequenced small RNA (sRNA) libraries from P. tricornutum under normal (PT1), nitrogen-limited (PT2) and silicon-limited (PT3) conditions. A total of 13 miRNAs were identified. They were probable P. tricornutum-specific novel miRNAs. These miRNAs were differentially expressed in PT1, PT2 and PT3, and their potential targets were involved in various processes. Our results indicated that P. tricornutum contained novel miRNAs that differed from miRNAs of other organisms and that they might play important regulator roles in P. tricornutum metabolism.