Caenorhabditis elegans

GS Paper III Science and Technology

Context

Caenorhabditis elegans, also called “the worm,” is used a lot in science to study how brains and cells work.

It was the first animal to have all its genes and brain connections figured out.
These worms grow fast and become adults in just 3-5 days after being born from eggs.

Caenorhabditis elegans is a small, transparent nematode. It lives freely in temperate soil environments.

The name C. elegans comes from a blend of Greek and Latin words meaning “recent,” “rod-like,” and “elegant.”
Key Traits of Caenorhabditis elegans:
- C. elegans is an unsegmented pseudocoelomate organism, meaning it lacks segmented body divisions and has a fluid-filled body cavity.
- It does not have respiratory or circulatory systems, distinguishing it from more complex organisms.

Nemotode

It is also known as roundworms or eelworms.
Habitat: They reside in soil, freshwater, marine environments, and within other organisms.
Eating habit: feeding on microorganism

- The majority of Caenorhabditis elegans individuals are hermaphrodites, capable of producing both eggs and sperm.
  - However, there are also a few males among the population.
- Male Caenorhabditis elegans possess unique tails specialized for mating, which include spicules, structures used during copulation.

Pseudomonas vranovensis is a harmful bacteria found where Caenorhabditis elegans naturally lives.
- This bacterium produces a tiny molecule called sRNA.
When the worms eat this bacterium, they also take in the sRNA.
- The sRNA changes the worms’ eating habits so they avoid the harmful bacteria in the future.
P. mendocina:
- P. mendocina, another bacterium in C. elegans’ habitat, is not harmful but a food source.
- Worms trained to avoid pathogenic P. vranovensis also avoided feeding on non-pathogenic P. mendocina.
- Researchers suggest that the “loss of memory” around the fifth generation might occur to re-learn the advantage of consuming P. mendocina.

DNA is like a ladder made of phosphate and sugar molecules.
- Each sugar unit is attached with four types of chemical bases: adenine (A), cytosine (C), guanine (G), and thymine (T).
P. vranovensis bacteria have about 6-7 million rungs in their DNA.
- It contains around 5,500 genes.
- Each gene provides instructions for making a protein.
RNA is similar to a half-ladder or a comb, with a spine made of phosphate and sugar molecules, and four types of bases: A, C, G, and uridine (U).
During a process called transcription, a cell copies the sequence of bases in a gene from DNA to RNA.
- This RNA, known as messenger RNA (mRNA), carries the genetic information to ribosomes.
sRNA and Gene Expression:
- Some genes produce sRNA instead of mRNA and proteins.
- sRNA can interact with proteins and other RNAs.
  - It influences gene expression positively or negatively.
Experiment with C. elegans:
- Researchers at Princeton University discovered that C. elegans worms ingested a 124-tine sRNA from P. vranovensis bacteria.
  - This sRNA reduced the expression of a gene called maco-1 in the worms.
    - It is also found in humans and plays a crucial neurological role.

Genes identified in Caenorhabditis elegans that affect its development are also found in the human genome.
Mutations in these genes have been linked to limb deformities in humans.

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