Biology Reference
In-Depth Information
Chapter 19
THE ROLE OF ATOMIC FORCE MICROSCOPY
IN ADVANCING DIATOM RESEARCH INTO
THE NANOTECHNOLOGY ERA
Michael J. Higgins a and Richard Wetherbee b
a ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute,
AIIM Facility, Innovation Campus, University of Wollongong, Wollongong NSW 2522, Australia
b Botany Department, University of Melbourne, Victoria, 3000, Australia
mhiggins@uow.edu.au
19.1 INTRODUCTION TO GENERAL DIATOM BIOLOGY
Diatoms are unicellular, micro-sized algae abundant in most of the world's
marine and freshwater habitats. When observed under a light microscope,
diatoms are strikingly beautiful organisms because of the transmission
of brilliant yellow-green to golden-brown colours from their intracellular
photosynthetic pigments. They come in diverse shapes and sizes ranging
from ive to hundreds of microns and are easily distinguished by their highly
elaborate, mineralized cell walls composed of micro- and nanostructured
segments and appendages ( Fig. 19.1a ) . Planktonic diatoms live free-loating
in open water, while benthic diatoms reside at the water-sediment interface
or adhere to any submerged substrate, including sand and rocks, the surface
of larger organisms and man-made structures. 1
The cell wall of diatoms, termed the frustule, is composed of silica and
consists of two overlapping halves or thecae that fasten together like a Petri
dish. 2 Each theca is composed of a valve and one or more rings of silica called
girdle bands that run around the circumference of the frustule and permit
cell growth following division ( Fig. 19.1b ). A major valve feature, called
 
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