title: QUANTITATIVE NANOMECHANICAL MAPPING OF MARINE DIATOM IN SEAWATER USING PEAK FORCE TAPPING ATOMIC FORCE MICROSCOPY(1).
abstract: It is generally accepted that a diatom cell wall is characterized by a siliceous skeleton covered by an organic envelope essentially composed of polysaccharides and proteins. Understanding of how the organic component is associated with the silica structure provides an important insight into the biomineralization process and patterning on the cellular level. Using a novel atomic force microscopy (AFM) imaging technique (Peak Force Tapping), we characterized nanomechanical properties (elasticity and deformation) of a weakly silicified marine diatom Cylindrotheca closterium (Ehrenb.) Reimann et J. C. Lewin (strain CCNA1). The nanomechanical properties were measured over the entire cell surface in seawater at a resolution that was not achieved previously. The fibulae were the stiffest (200 MPa) and the least deformable (only 1 nm). Girdle band region appeared as a series of parallel stripes characterized by two sets of values of Young's modulus and deformation: one for silica stripes (43.7 Mpa, 3.7 nm) and the other between the stripes (21.3 MPa, 13.4 nm). The valve region was complex with average values of Young's modulus (29.8 MPa) and deformation (10.2 nm) with high standard deviations. After acid treatment, we identified 15 nm sized silica spheres in the valve region connecting raphe with the girdle bands. The silica spheres were neither fused together nor forming a nanopattern. A cell wall model is proposed with individual silica nanoparticles incorporated in an organic matrix. Such organization of girdle band and valve regions enables the high flexibility needed for movement and adaptation to different environments while maintaining the integrity of the cell.
authors.affiliation: Division for Marine and Environmental Research, Ruđer Bošković Institute, Zagreb 10000, CroatiaBruker Nano GmbH, Mannheim 68165, GermanyDivision for Marine and Environmental Research, Ruđer Bošković Institute, Zagreb 10000, Croatia.
authors.forename: Galja
authors.initials: G
authors.lastname: Pletikapić
authors.affiliation: Division for Marine and Environmental Research, Ruđer Bošković Institute, Zagreb 10000, CroatiaBruker Nano GmbH, Mannheim 68165, GermanyDivision for Marine and Environmental Research, Ruđer Bošković Institute, Zagreb 10000, Croatia.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Berquand
authors.affiliation: Division for Marine and Environmental Research, Ruđer Bošković Institute, Zagreb 10000, CroatiaBruker Nano GmbH, Mannheim 68165, GermanyDivision for Marine and Environmental Research, Ruđer Bošković Institute, Zagreb 10000, Croatia.
authors.forename: Tea Mišić
authors.initials: TM
authors.lastname: Radić
authors.affiliation: Division for Marine and Environmental Research, Ruđer Bošković Institute, Zagreb 10000, CroatiaBruker Nano GmbH, Mannheim 68165, GermanyDivision for Marine and Environmental Research, Ruđer Bošković Institute, Zagreb 10000, Croatia.
authors.forename: Vesna
authors.initials: V
authors.lastname: Svetličić
keywords: Cylindrotheca closterium; Peak Force Tapping atomic force microscopy; Young’s modulus; atomic force microscopy; deformation; diatom cell wall; elasticity; marine diatom; nanomechanical properties