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Wellcome Image of the Week: Diatom

4 Oct, 2013
Diatom

Diatom

You could mistake it for a pattern created with a classic “Spirograph” toy, but our image of the week is actually algae. Diatoms, a form of algae, are single-celled organisms that can exist as colonies. They are found in most aquatic environments, and are responsible for a significant amount of marine photosynthesis.

Diatoms are encased in a siliceous shell, called a frustule and it is these that form the beautiful patterns. Many of the most decorative diatoms are only found as fossils in the earth, and so are covered in debris that needs to be removed before they can be photographed. The resulting clean diatoms are spread over a slide and examined under a microscope and only the most perfect specimens are chosen. This diatom pattern was painstakingly prepared by Klaus Kemp.

The sample must then be transported and placed onto a second slide with microscopic precision to form the correct pattern: the arrangement in the image above is only 1mm wide. Supposedly, Victorian mounters used a pig’s eyelash mounted in a needle holder to lift and transfer the diatoms, but we imagine that Klaus used a more modern technique. The second slide has a ‘tacky’ surface so that the diatoms stick to it. This is necessary because the arrangement has to survive being flooded with mounting fluid and covered with a coverglass. If this fails, all the previous hours of work are lost!

The photograph of this arrangement was taken by Spike Walker, using Rheinberg illumination. To show the whole arrangement, Spike had to ‘stitch’ together overlapping photographs taken by a high-powered microscope, since a lower powered microscope would lose the stunning detail.

As well as being very photogenic, diatoms could be very useful to us in the field of nanotechnology. Nano-electrics require silicon, which can be obtained from the diatoms’ silica frustules. And since diatoms’ pores have binding sites for biological molecules, they could be used as tiny biosensors, detecting things like antibodies.

If you like this image, why not browse through other stunning examples of Spike’s diatom photographs on Wellcome Images, for example here and here.

Image credit: Spike Walker, Wellcome Images.

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