Posted by Ryan Farmer on Wed, Jan 7, 2015 @ 12:00 PM
In Shakespeare’s Romeo and Juliet, Juliet laments “wherefore art thou Romeo” to later question him to “refute thy name”. This is the classic issue of whether our names define who we are or just identify what we have already become. Though cyanobacteria do not receive any stage cues in this tragedy, they were around in Shakespeare’s time. In fact they have been around for eons. Long before humans came along and gave them names.
These organisms have two different names: cyanobacteria and blue-green algae. Unlike a ‘Montague’ neither of these names dictate what they can or cannot do. Instead they are just descriptive identifiers of what they already are. This raises the question of “why two names?” Does a cyanobacterium of any other name smell just as … foul? To answer this we must dissect each name.
The first part of both names refers to the same color. Cyan is just another name for a teal or blue-green color. Cyanobacteria are indeed both blue and green, and these colors come from pigments that are involved in photosynthesis (the process of capturing light energy to convert carbon dioxide and water to sugar). Blue comes from a protein known as phycocyanin that is, more or less, unique to cyanobacteria. Green comes from chlorophyll, which is much more common and also makes plants like vegetables, grasses, and tree leaves green as well. One nice thing about these pigments is that they can be detected with a fluorometer. So if you have a chlorophyll fluorometer, you can measure all algae; if you have a phycocyanin fluorometer, you can more specifically measure just cyanobacteria.
The second part of their name (bacteria vs. algae) does have a distinction. Blue-green algae are bacteria in the true sense of the biology 101 definition: no nucleus, different ribosome, etc. Does being a bacterium exclude them from being algae? Some scientists say so; thus giving rise to the two names. This is because, to most biologists, algae are eukaryotes not bacteria. (Beagle’s Stephanie Smith touched on this distinction in one of our earliest blogs). But “algae” can be more loosely defined. The broadest definition is that algae have chlorophyll for photosynthesis but are not plants. Keeping with this looser definition, then the blue-green algae name remains relevant.
So what’s in a name? For cyanobacteria/blue-green algae, their name is purely descriptive. Some parts are accurate, others may be misleading. To quote Shakespeare once again, “this above all: to thine own self be true.” Regardless of what we call them, these microbes have grown to become aquatic photosynthesizers and will continue to be true to this regardless of how many times we change their names.