Imaging Algae

I have taken my first images of the algae using the Phenom scanning electron microscope (SEM) at the Applied Research Center (ARC).  These pictures have shown that there was too much algae on the stub.  I need to be able to image a particular frustule and then return to that same individual multiple times after modifying it or examining it in another piece of equipment. In addition, I must be sure that the patterns seen on the frustule are indeed the actual structure, not a result of charging up.  Charging up is when electrons build up in a region on the surface of whatever is being imaged.  This causes the paths of the imaging electrons to be distorted and so the resulting image is skewed.  This usually shows up as static-like lines across the image or just very bright sections.  However, the effect of charging up can be much more localized so as to distort minute features, especially as the magnification is increased.  From these stubs, I did find that previously dried samples cannot be used unless they are washed and filtered significantly more.  The algae are just simply not separated from the sediments and other material.  For the same reason, centrifugation can’t be used because it creates a solid mass rather than separating.  The stubs that had algal samples that had been continuously suspended produced much better images.  These samples were cleaned using room temperature and 40C 30% hydrogen peroxide.  These cooler temperatures revealed a sample that had a larger proportion of intact frustules than previous cleanings.  These cooler temperatures allowed for new algal structures to be viewed but were not terribly effective at removing the sediments and other material that doesn’t interest us.

A Thalassiosira frustule embedded in sediment.

A Thalassiosira frustule embedded in sediment.