Why C. elegans?
In 2002, Sydney Brenner, H. Robert Horvitz and John E. Sulston shared the Nobel Prize in Medicine for their work using C. elegans to study the genetic regulation of organ development and programmed cell death. Brenner’s Nobel lecture, “Nature’s Gift to Science,” reflects upon the profound impact of model organisms on the ability of scientists to understand the natural world and how nature’s bounty serves as both a source of inspiration and innovation (Brenner, 2002). It is an unfortunate reality that natural history is no longer included in many state standards for life sciences. For many science teachers, it was their high school experiences observing, cataloging, dissecting, and studying plants and animals that inspired them to become science teachers. Today, virtually every branch of the life sciences focuses on the molecular. Hence, the California state standards and the new Next Generation Science Standards are weighted heavily toward the chemistry of DNA, RNA, proteins, enzymes, neurotransmitters, hormones, the plasma membrane, receptor proteins and gene regulation. This leaves very little time in the curriculum to cover the other standards, let alone many of the exciting parts of science that no longer are included in the standards.
The nematode C. elegans offers an elegant solution to this dilemma. They are exciting for students and handy for teachers, as they can be used to study virtually every aspect of life science from chemotaxis, thermotaxis and mechanosensation to drug or alcohol interactions, population ecology, metabolism, respiration, reproduction, development, aging, and genetics. For example, nematodes can be used to study membranes and osmosis due to their semi-permeable cuticle (Solomon, et al, 2004), and they can be used to study nicotine addiction, because their response to nicotine withdrawal is similar to that of humans (Feng, et. al., 2006). C. elegans are also commonly used by scientists in novel research. C. elegans was the first multicellular organism to have its entire genome sequenced (The C. elegans Sequencing Consortium, 1998). Scientists were able to figure out how RNAi (RNA interference) worked by studying C. elegans, leading to a Nobel prize for Craig Mello and Andrew Fire in 2006 (Fire, et al, 1998). The first apoptosis genes were discovered in C. elegans in the Brenner lab, (Hengartner, et al, 1992).
C. elegans are easy and safe to use, both for humans and the environment. They are a common member of many soil communities. Presently, there are not many model organisms available for high school use. Most vertebrates are either cost prohibitive, illegal in schools, or pose ethical dilemmas for many students and teachers. Some teachers use isopods (roly-polies) or earthworms, both of which can be collected by teachers or students at no cost. However, neither are commonly used in real scientific research, they are not easily obtained throughout the year, and they are not easy to propagate for long periods of time. Fruit flies, in contrast, are a common model organism used by scientists, but they are substantially more expensive than worms, harder to keep alive for extended periods, and tend to colonize the classroom when they inevitably escape their storage tubes. Nematodes, in contrast, do not fly and always remain on their Petri dishes. Culturing them is as simple as flaming a metal spatula and transferring a chunk of agar from one Petri plate to another. Plates of worms can be stored at room temperature for weeks. Sometimes, viable worms can be recovered from plates that have sat for months and are so dry that the agar has cracked and peeled. Worms can also be frozen for long-term storage.
In short, C. elegans is uniquely well-suited for use in a middle or high school biology classroom. They are incredibly easy and inexpensive for teachers to obtain and propagate. They are fun, exciting, and simple for teenagers to handle. C. elegans is a real model organism used by thousands of scientists throughout the world, including two Nobel prize-winning teams. However, what I like most about these C. elegans modules is that they provide an engaging hook to keep teenagers excited about the molecular and cellular portions of the Life Science curriculum, while providing much needed practice with common tools of biotechnology such as the micropipette.
C. elegans at High School
Biology and Biotechnology students at my school have the opportunity of working with C. elegans worms, a state of the art model organism that has produced two Nobel Prize winning research projects. The highlight of the C. elegans curriculum is the use of digital microscopy to record the movements of worms that have been exposed to ethyl alcohol (compared to control worms). Students use ImageJ software, from the National Institutes of Health (NIH) to track the movements of the worms and Excel, to calculate individual and mean velocities, standard deviation, and T-test analysis of their results. Students also do chemotaxis assays to determine whether various odorants are attractive or repellent to the worms. Please see the C. elegans links to the left for more information on this exciting curriculum and the international field of C. elegans research.