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Marine diatoms and their networks: an AFM study

Pletikapić, Galja; Berquand, Aleksandre; Mišić Radić, Tea; Svetličić, Vesna; Žutić, Vera Marine diatoms and their networks: an AFM study. In: Znanstveni susreti 3. vrste (7 July 2011 - 8 July 2011) Zagreb, Hrvatska. (Unpublished)

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Diatoms are unicellular microalgae responsible for about 20% of the world’s net primary production. They are also known for the species-specific design and ornamentation of their silica-based cell walls. This study highlights the capacity of atomic force microscopy (AFM) for measurement of nanomechanical properties of diatom cell wall and for investigating diatom extracellular polysaccharides with a subnanometer resolution. As a model organism we have selected Cylindrotheca closterium isolated from Northern Adriatic seawater. The unique characteristics of Cylindrotheca spp. cell wall are regions which are believed to be completely unsilicified. The nanomechanical properties were measured over the entire cell surface in seawater at a resolution that was not achieved previously. Based on nanomechanical measurements, we discovered silica nanoparticles in region that has been reported unsilicified and purely organic. A cell wall model is proposed with individual silica nanoparticles incorporated in an organic matrix. Such organization of cell wall enables the high flexibility needed for different movement modalities and adaptation to different environments while maintaining the integrity of the cell. Extracellular polysaccharide production by marine diatoms is a significant route by which photosynthetically produced organic carbon enters the trophic web and may influence the physical environment in the sea. Extracellular polymers (EPS) were visualized as fine fibers and networks with molecular resolution. The EPS represents a network of polysaccharide fibrils with two types of cross-linking: fibrils forming junction zones and fibril–globule interconnections with globules connecting two or more fibrils.

Item Type: Unpublished conference/workshop items or lecture materials
Uncontrolled Keywords: Diatoms; Cylindrotheca closterium; Extracellular polymers
Subjects: NATURAL SCIENCES > Biology > Botany
NATURAL SCIENCES > Interdisciplinary Natural Sciences > Marine Science
NATURAL SCIENCES > Interdisciplinary Natural Sciences > Environmental Science
Divisions: Division for Marine and Enviromental Research
Depositing User: Galja Pletikapić
Date Deposited: 24 Sep 2012 13:08

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