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Electron microscopes manipulate the relatively short wavelength of electrons (100,000 times shorter than the photons that make up visible light) to study the structures of microscopic objects. They create magnetic fields shaped into an electron-optical lens which works in a way analogous to a conventional optical microscope’s glass lens. Through this electron-optical lens, magnification of up to 10,000,000 times can be achieved with a resolution better than 50 pm (picometers, one trillionth of a meter).
Electron microscopy can be used to observe the ultrastructure of physical objects, which is the architecture of individual cells in the specimen. This has a range of applications in numerous fields, including semiconductors and data storage, biology, materials research and various industries that rely on the precise understanding and detection of minuscule parts of component materials. Aquatic sciences also frequently use electron microscopy, especially in the study of contaminants in water.
Understanding How Beaches Influence Long-Term Oil Pollution
The Prestige oil tanker sank off the coast of Galicia, Spain in 2002, spilling 77,000 tonnes of oil into the ocean and thereby contaminating the local seawater and beaches. To understand how the changing landscapes of beach sands was affected by oil contamination, a team of researchers from the Universities of Vigo (Spain) and Montpelier (France) sampled seawater samples from different areas using electron microscopy to identify the levels of oil they contained (Fernández-Fernández et al., 2011).
Finding Invisible Viruses in Seawater
A University of Maryland team used transmission electron microscopy to reveal prophages, invisible viruses which become part of the micro bacterial ecosystem by integrating their DNA into hosts, in seawater (Chen et al., 2006). In transmission electron microscopy, the beam is projected through the specimen to generate the magnified image. The strategy demonstrated incorporates genome research with traditional microbiological techniques to find these invisible viruses with electron microscopy.
Testing Denitrification of Irrigation Water
Electron microscopy has also been used to test a new method for removing nitrates from synthetic infiltrate used in agriculture. In the method, methanol bacteria are added to the water, which had a significant effect on nitrate levels in soil irrigated by the water. Electron microscope images of soil samples supported the researchers’ findings that nitrates were removed from the water by the addition of methanol bacteria (Siripattanakul et al., 2010).
Identifying Potentially Toxic Microalgae and Poisoning Acid
Another University of Maryland team used electron microscopy to identify potentially toxic species of microalgae in water in the Chesapeake Bay, an estuary in the northeast United States. The researchers used transmission electron microscopy to study samples of water and found six species of Pseudo-nitzschia – potentially toxic diatom microalgae – as well as finding information on domoic acid levels in the water. Domoic acid is a neurotoxin and the cause of amnesic shellfish poisoning, which can harm humans and other predatory animals when they eat shellfish, sardines, and anchovies in which it has accumulated.
Using This Research to Avoid Contaminations in Water
The examples above have all used electron microscopy to better understand the ways in which waters around the world can be contaminated by human materials and pollutants or by microscopic bacteria. In each case, and in many others, the electron microscope’s ability to allow researchers to observe, identify and study cell-sized organisms has enabled a clearer view of water contamination. This better understanding ultimately leads to new ways of avoiding contamination.
In some cases, as in the denitrified water, electron microscopy can be used to test novel decontamination techniques, such as adding bacteria to water to stop it from contaminating the soil.
- Chen, F., Wang, K., Stewart, J. and Belas, R. (2006). Induction of Multiple Prophages from a Marine Bacterium: a Genomic Approach. Applied and Environmental Microbiology, 72(7), pp.4995–5001.
- Fernández-Fernández, S., A.M. Bernabeu, F. Bouchette, D. Rey, and F. Vilas. "Beach Morphodynamic Influence on Long-term Oil Pollution: The Prestige Oil Spill." Journal of Coastal Research, 2011, 890-93. https://www.jstor.org/stable/26482301
- Siripattanakul, Sumana, Carlee J. Pochant, and Eakalak Khan. "Nitrate Removal from Agricultural Infiltrate by Bioaugmented Free and Alginate Entrapped Cells." Water Environment Research 82, no. 7 (2010): 617-21. http://www.jstor.org/stable/27870353.