Caption: Fresh water pennate diatom colony (Asterionella sp.). Asterionella is a genera of planktonic fresh water diatoms found worldwide.The cells are joined at the broadest apex by mucilage pads to form stellate or spiral colonies. Some populations are particularly susceptible to chytrid infestations. This genus is a biological indicator of hard water. The body or frustule of each pennate cell in the colony is composed of two halves which fit tightly together. The cell walls contain silica dioxide (glass) which are preserved in deposits known as diatomaceous earth. Once hardened into rock it is called diatomite and can be used for many purposes including filters, fillers and abrasives. There are many phytoplankton diatom genera that are an important part of the food chain. Diatoms represent about 25% of the plant biomass in the world. Found both in fresh water and salt water these microscopic unicellular plants are important biomass and oxygen producers. Through their photosynthesis, greenhouse gasses are converted to organic material and they therefore play a decisive role in the global carbon dioxide circulation. When individual cells die they remain as siliceous (silica dioxide) cell walls and sink to the bottom of the lake or ocean. Research has shown that the walls of fossil diatoms can give valuable information about past environment and climate conditions and serve as indicators for historical dating of sediments. Industries use the diatom silica walls in the form of diatomaceous earth for polishing material and for filtering wine and beer. In the field of nanotechnology the motility of such tiny cells and the silica cell wall design has been used as a pattern for car wheels. Omega-3 fatty acids of the diatoms have been found to benefit the nervous system.
Magnification*: x135
Type: SEM
Copyright 2009 Dennis Kunkel Microscopy, Inc.
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