Poster’s note: Some people have requested that I try to relate scientific topics to a mostly non-scientific audience (a la Ira Flatow of “Science Friday”). I hesitated to embark on this line of discussion as I am not a scientific expert. However, the benefits of clarifying some incorrect impressions that the public has of scientists, debunking scary scientific myths, and explaining basic scientific concepts far outweigh any negatives I can think of. Any person more knowledgeable on a subject I may post is more than welcome to correct me. Also, feel free to suggest topics or post questions. If I feel that I can impart knowledge on the subject, I’ll cover it. And with that disclaimer, let’s get it on.
Biologists have chosen certain organisms as model organisms because frequently, we can’t study whole organismal phenomena in humans. What does that mean? Well, if I wanted to study where one particular muscle gene functions in the whole body, I can’t delete that gene from Johnny and see if that gene works in his heart or in his bicep. (The heart’s just a muscle, folks.) I might get lucky if Johnny’s bicep shrinks, but it would suck if Johnny had to have a heart transplant. The public frowns on that sort of research. So, scientists decided to use non-human organisms for basic research.
You’ve all heard of one—Mus musculus (the scientific name), or mice. Those cute mice steal all the attention from a small zoo of other model organisms. Just to name a few: E. coli (Escherichia coli), baker’s or brewer’s yeast (Saccharomyces cerevisiae), sea urchins (Arbacia punctulata), fruit flies (Drosophila melanogaster), zebrafish (Danio rerio), African clawed frogs (Xenopus laevis), rats (Rattus norvegicus), a plant related to mustard and cabbage (Arabidopsis thaliana), and my favorite, worms (Caenorhabditis elegans). Scientists chose these organisms for a variety of reasons including short lifespan, low maintenance required, ease of regeneration, price, and similarity to human physiology.
I work in a Caenorhabditis elegans or C. elegans lab. By the 1970s, the scientist Sydney Brenner had chosen this small worm to study neurobiology (biology of neurons which comprise the brain). Through his significant work in animal development and neurobiology, Brenner established C. elegans as a model organism. These harmless nematodes, or round worms, normally reside in the soil in temperate climates. Only 1mm long and transparent, they make fantastic research subjects. They eat E. coli, a harmless strain and cheap source of food, and squirm around all day.
A few quirks distinguish worms from the rest of the model organisms. The wildtype or “normal” individual is a hermaphrodite, meaning it contains both male and female sex organs. (Males comprise 0.05% of the population.) The individual (“she”) lays fertilized eggs that take about three days to reach adulthood. Also, each wildtype adult worm has exactly 959 somatic cells! Somat-o-what? Sorry. All of the cells in your body that aren’t generating eggs or sperm are called somatic cells. Most of them. The cells that generate eggs and sperm are called germ cells. Back to the point—exactly 959 cells! In case that doesn’t sound remarkable, most multi-cellular organisms that we have studied do not have the same number of cells. A whole organism. 959 cells! Count ‘em.
Oh wait, some guy did count them. In 1983, John Sulston submitted a cellular fate map in which he tracked the origin, development, and fate of each cell in the worm. Sulston said that watching the worms develop from one cell to 959 cells was like gently shaking a bowl of marbles and keeping your eye on one of them at a time. For this tedious and remarkable work, Sulston shared the Nobel Prize with Brenner and H. Robert Horvitz in 2002.
Hundreds of labs around the world use worms to study biological processes ranging from gross anatomy, cell division to regulation of small molecules within cells. The way processes occur in worms can be analogous to the way they occur in humans, so information gathered from the little animals is powerful. Plus, they’re cute. Need a better reason to work with them?