Image Credit From Nature
Basic research is not simple research: by researching the fundamental activities in cells, researchers can target genes that cause disorders and create new molecules to combat disease. In order to conduct basic research, scientists use model organisms because they have simplified cellular systems that reproduce quickly, are easy to maintain, and are cost efficient. C. elegans are one of these model organisms, including fruit flies, yeast, and mice. Since C. elegans are eukaryotic, they have more similarities to humans than bacteria and they are easy to store and study.
C. elegans are interesting because they have specialized cells like neurons, muscle cells, a digestive and excretory system, and a reproductive system. Compared to a fruit fly, though, C. elegans were the first multicellular organism to have its genome completely sequenced, so basic genetic research is much easier with C. elegans.
What do C. elegans look like?
C. elegans are small and transparent, but you can still see them! They are a roundworm, or nematode, that can reach approximately one millimeter in length. C. elegans can be found in temperate soil environments, and they feed on bacteria that help decay decomposing plants. If you get some dirt, there’s a chance there are C. elegans!
But in labs, C. elegans are usually fed E. coli bacteria, specifically the strain E. coli OP50. As a result, they do not cause disease, and they only eat bacteria. C. elegans are found to be either males or hermaphrodites. Hermaphrodite C. elegans can reproduce by themselves or with males. Hermaphrodite has 959 somatic cells while males have 1,031 cells; in comparison, humans have around 37.2 trillion cells. As a result, C. elegans have been much easier to study for genetic and developmental research.
C. elegans and Aging Research
C. elegans don’t live very long: only 2 to 3 weeks! They hatch from fertilized eggs, and they undergo molting processes out of their polysaccharide exoskeleton, called a cuticle. Each time, they grow larger from 250 micrometers to 1,100 micrometers (1.1 mm).
When C. elegans do not have enough space or food, they can enter a stage called dauer. Dauer larvae are thinner, and their “mouth” becomes plugged, preventing feeding. These larvae do not eat, but they are highly stress-resistant and will live longer. As a result, C. elegans have become model organisms for aging research.
C. elegans Genetics
C. elegans have six pairs of chromosomes (we have 23 pairs in comparison). Hermaphrodites have a pair of X chromosomes while males have a single chromosome (XX), called hemizygous X. Since we have been able to sequence the entire C. elegan genome, we know that their entire genomes are approximately 26% introns, 20, 470 protein coding genes, and approximately 16,000 RNA coding genes (associated with gene expression and regulation). As a result, research on C. elegans has been able to pinpoint different genes.
C. elegans Neurology and Behavior
C. elegans only have 302 neurons, so its circuit has been thoroughly studied in its connectome, and their neurons can be studied with their behavior from eating, movement, and reproduction. Some studies have been able to knock out certain genes to produce mutant C. elegans to study how their behaviors compare to wild-type C. elegans.
How to Study C. elegans
In order to study C. elegans, we have to start cultures. To create a subculture, we start with two types of plates: plates with E. coli and plates with C. elegans. We will wash each of the two types of C. elegans so that we can pipette them into a colony of E. coli to feed on.
First, we label one agar plate full of E. coli for the wild type C. elegans and another for mutant C. elegans. We do the same thing for two microcentrifuge tubes. We then add 1 mL of wash buffer onto the agar plates and incubate them for 30 seconds. We then tilt the agar plates so they allow the worms to collect onto one side of the plate and begin eating the E. coli. We then transfer the C. elegans from the agar plates into their respective microcentrifuge tubes. After 2 minutes, the C. elegans in the tubes should settle onto the bottom, and then we transfer C. elegans back onto the plates and let them feed on the E. coli.
What type of behaviors would you want to study from C. elegans?
