Thursday, April 14, 2011

Oh, and one more thing

Just about an hour ago I received an email from a fellowship committee that I did not receive a dissertation completion fellowship. While it is possible that my application was sub-par, or that my letter of reference was weak, I can't help but wonder if the committee read my application and thought, "Diatoms? In my entire life I've never heard of such creatures. Why should I care about them now, especially in such dire financial times, when I could fund an applicant who studies something important, like cancer?".

Well, I'm here to set the record straight. Diatom research may not cure cancer (as far as we know), but there are so many applications of diatoms to people's everyday lives.
I'll start with an anecdote. Before I knew anything about diatoms, I took an animal science course at UMass. During one class we visit a farm, where we learned that a popular method for dealing with intestinal parasites was to add diatomaceous earth to the animal's feed. Diatomaceous earth (DE for short) consists of the glass remains of dead diatoms. In some parts of the earth there are huge deposits of DE from highly productive oceans. The DE is inorganic and accumulates in sediments.
The tiny glass bits of broken diatoms act like tiny microbial razors to cut up the offending parasites. From that class on, I knew diatoms were special. Apparently, diatomaceous earth also controls worms in dogs and cats (who knew?!!).

Image: Diatomite mine in Nevada. That white, chalky stuff is all diatoms! (ref 1)

Here's just one more reason people should know and care about diatoms. As I mentioned in the previous post, they are abile to biologically transform silica to from an intricate and repeatable silicate structure, called a frustule. Frustules are amazingly beautiful and have been the object of many artists' attention.

Images: diatom art (ref 2)

Now for the applied part. Humans would really like to capture the inherent ability of diatoms to create this repeatable nanostructure to create highly useful products like semiconductors (ref 3). Current industrial processes are hugely energy intensive, and yet diatoms do it all of the time using proteins. There is also much interest in using diatom frustules for drug delivery (ref 4) and even as an energy harvesting element in solar cells (reviewed in ref 5). The tiny diatom pores in the biological solar cells greatly increases efficiency compared to traditional solar cells.

Image: layout of a diatom-titanium dioxide thin film solar cell (ref 6)

Those are just two HUGE ways that diatoms affect the lives of everyday people. I may not have made that clear enough in my 750-word application, but I hope that I have convinced anyone who reads this that diatoms are worth of our attention.

1. Diatomite image:
2. Diatom art:;
3. Gordon et al. The glass menagerie: diatoms for novel applications in nanotechnology. Trends in Biotechnology 27(2): 116-127.
4. De Stefano et al. Inerfacing the nanostructured biosilica microshells of the marine diatom Coscinodiscus wailesii with biological matter. Acta Biomaterialia 4(1): 126-130.
5. Chapter 35 in: The diatoms: applications for the environmental and earth sciences (vol II). 2010. J. Smol, editor. Cambridge University Press. 686 pages.
6. Greg Rorrer lab, Oregon State University.

Sunday, April 10, 2011



The leader in libations, the king of the kitchen, this tiny organism rises to the top when it comes to making delicious food. Of course, I'm talking about the fomenter of fermentation, Saccharomyces cerevisiae, more commonly known as yeast.

Scanning electron microscope images of yeast cells (source: Yeast cells divide by a process called budding, present on these cells as small round dots.

Under low oxygen conditions, Saccharomyces, or "sugar fungus", can perform a very special form of metabolism called ethanol fermentation. The production of CO2 gas causes bread to rise and gives beer and champagne its fizz. And the ethanol? Well, you know. But, of course, the yeast really care about the energy produced by fermentation that sustains growth and reproduction. I'll note here that yeast grows a lot more efficiently using aerobic respiratory metabolism (like us humans) than anaerobic fermentation.

Making beer is fun! At the Microbial Diversity course in Woods Hole, MA, students learn first-hand about yeast fermentation.

Yeast in the Environment

In the family tree of life, S. cerevisiae belongs to the domain Eukarya (meaning it's more closely related to humans than to bacteria), and the phylum Fungi. While we generally refer to S. cerevisiae as 'yeast', there are many species that belong to this broader yeast group. Some species have real benefits to us (like baker's yeast), while we don't know very much about
many (like most organisms...), and others cause illness (e.g. Candida species). In the environment, fungi play an important role in cycling nutrients by decomposing organic matter so that nutrients become available for plants and micro-organisms. They are the "filters" of the environment, so it's no surprise that they do a great job cleaning up polluted land. S. cerevisiae and other yeasts are known to remediate Chromium (1), a poisonous metal that was made famous in the Julia Roberts film "Erin Brockovich".

Yeast is a relatively simple eukaryotic organism, being single-celled and easy to grow in a laboratory setting. For these reasons, it has become a model organism for scientific research. We have learned a lot about ourselves through understanding the biology of yeast cells. Some truly revolutionary analytical tools were developed using yeast, such as the two-hybrid assay (2), which has revealed insights into cancer biology (3), endocrine disruptors (4), and cell signaling (5), among much more.

We all can appreciate a tiny organism that can make delicious tasting food and beverages. But now that we know that there is so much more to this important microbe, we should all bow down to the king of the kitchen.

1. Ksheminska et al., Process Biochemistry, 2005: 1565-1572.
2. Interested? Check out Wikipedia for more information!
3. Li and Fields, FASEB Journal, 1993: 957-963.
4. Nishihara et al., Journal of Health Science, 2000: 282-298.
5. Staudinger et al., Journal of Cell Biology, 1995: 263-271.