Caenorhabditis elegans, often referred to as C. elegans, is a tiny, free-living nematode widely adopted in scientific research. This transparent roundworm, typically about 1 millimeter in length, offers a remarkably simple yet complete biological system. Its rapid life cycle, well-defined genetics, and transparent body make it an invaluable model organism for studying fundamental biological processes, including development, neuroscience, and aging.
Natural Feeding Habits
In their natural habitats, C. elegans are found in microbe-rich environments like decaying fruits and vegetation. They are primarily bacterivores, meaning their diet consists mainly of bacteria. The specific bacterial species they consume are diverse and depend on the microbial community present in their immediate environment.
Their natural diet includes various bacterial phyla, such as Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria, which are abundant in their habitats. While some bacteria support robust nematode growth, others can impair growth or even produce toxins. This diverse diet highlights their adaptability to microbial food sources in decomposing organic matter.
Cultivating C. elegans in the Lab
In laboratories, C. elegans are cultivated on a standardized diet for consistent experimental conditions. The most common food source is Escherichia coli (E. coli), specifically the OP50 strain. This strain is widely used because Sydney Brenner, who pioneered C. elegans as a model organism, maintained his worms on it.
OP50 is a uracil auxotroph, requiring uracil from its environment, which restricts its growth on Nematode Growth Medium (NGM) agar plates. This controlled growth prevents an overly thick bacterial lawn, allowing easier microscopic observation of the worms. A consistent diet is paramount for reproducible research, enabling studies of genetics, development, aging, and disease without confounding dietary variables. While OP50 is standard, other bacterial strains like HT115 (for RNAi experiments) or HB101 (for liquid cultures) can be used for specific research, and chemically defined diets are sometimes utilized to precisely control nutrient intake.
The Unique Way C. elegans Eats
C. elegans possesses a specialized feeding organ, the pharynx, a neuromuscular pump connecting the mouth to the intestine. This tubular, muscular structure ingests, concentrates, and grinds bacterial food. The pharynx operates through rhythmic pumping: a cycle of rapid contraction and relaxation.
During contraction, radially oriented pharyngeal muscles pull the lumen open, creating a vacuum that sucks in liquid and suspended bacteria. A rapid relaxation then expels the liquid while trapping bacteria. This efficient filtering allows the worm to ingest bacterial particles while expelling excess fluid. The trapped food moves posteriorly through the pharynx into the intestine, where digestion occurs.