Project description:The biomolecular composition of diatom underwater adhesives remains unknown as does the precise mechanism by which the secretion of adhesive material from the raphe slit is coupled to an intracellular motor that provides the force for cell motility. In this study we have characterized the previously identified frustule associated components (FACs) from the common fouling diatom Craspedostauors australis and demonstrated that they form a continuous cell wall coating. The FACs are encoded by a single polypeptide (caFAP1) that has a domain structure of alternating cysteine-rich and PTS-rich regions which is reminiscent of the gel-forming mucins. CaFAP1 is notably absent from the raphe slit and therefore does not play a direct role in cell adhesion and motility but may rather play an important role in lubrication and self-cleaning that is required for epipsammic benthic diatoms that grow attached to sand grains, or moving through sand.
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: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: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.