What is Caenorhabditis elegans?

Enlarge

From-I.-Chin-Sang
From I. Chin-Sang

Caenorhabditis elegans is a very small, transparent nematode, measuring around one millimeter in length (Wood, 1988). Though they are little in size, using them as model organisms has led scientists to discover great things. In the lab, these worms are grown on agar plates with Escherichia coli for food. Under optimal conditions, around 20 degrees Celsius, the worms display an average life cycle of three days, from egg through adult (Wood, 1988).

Worms are either hermaphrodites or males. The two sexes can be distinguished by the shape of their tails. Hermaphrodites have a long, slender tail with a tapered-end. Males have a rounded, hook-like tail. Hermaphrodites can either self-fertilize, or mate with male worms, to produce viable progeny (Wood, 1988).

Thus, by manipulating temperature and mating conditions, we can prepare specific genetic experiments to suit our research needs. For instance, worms of the same genetic makeup, or genotype, can be produced in a matter of days, by allowing hermaphroditic worms to self-fertilize and reproduce. Knowing this allows us to keep track of the worms’ genotypes over many generations. Additionally, C. elegans was the first multicellular organism to have had its entire genome sequenced*, thereby allowing scientists to conduct experiments on the worms with a complete basic understanding of their molecular makeup (C. elegans sequencing consortium, 1998).

For the purposes of lab work, their known genome, quick reproductive rate, and ease of manipulation in a lab setting, are what make C. elegans worms model organisms.

* Note: Genome sequencing is a process in which the entire genomic sequence (DNA) of an organism is determined. This sequence is often referred to as a genetic code that can be “read.” Our DNA is made up of four nucleotides – adenine, thymine, cytosine, guanine – whose order within the genetic code makes us unique from other organisms and from each other. All living organisms store genetic information as DNA that can be decoded (Hartwell et al, 2011).