C. elegans Chemotaxis and Preservative Effects

ISEF Category: Cellular and Molecular Biology

Subcategory: Neurobiology  ·  Difficulty: Intermediate  ·  Setup: School Lab  ·  Time: 1 to 2 Months

The Hook

Tiny worms can tell you when a chemical messes with their senses. That makes C. elegans a neat model for studying how food preservatives may affect neuron-driven behavior. You can turn a simple plate assay into a real research project with dose-response data and public gene expression analysis.

What Is It?

This project studies chemotaxis, which means movement toward or away from a chemical cue. In C. elegans, special sensory neurons help the worm find food by following odors. AWC neurons are one of the key neuron types that drive attraction to certain smells.

Think of the worm like a tiny robot with a built-in odor compass. If a preservative changes how well that compass works, you may see weaker attraction, stronger avoidance, or no change at all. You are not just watching behavior. You are linking that behavior to public single-neuron RNA-seq data from CeNGEN, which can help you guess which gene modules may be involved.

Why This Is a Good Topic

This is a strong science fair topic because you can test a clear question, measure a real behavior, and connect your results to public molecular data. The setup is affordable compared with many neuroscience projects, and the readout is simple enough for a first-time researcher. You also get a nice biology bridge between genes, neurons, and behavior, which makes the project feel bigger than a basic worm assay.

Research Questions

• How does sodium benzoate concentration affect C. elegans attraction to a standard odor cue?
• What is the effect of BHT concentration on C. elegans chemotaxis index?
• Does exposure to sodium benzoate change worm attraction differently than exposure to BHT?
• To what extent does the odor choice change the measured preservative effect on chemotaxis?
• Which preservative dose produces the first measurable drop in attraction behavior?
• How does the response pattern compare between young and older worms?

Basic Materials

• NGM agar plate supplies for C. elegans culture and assays.
• Live C. elegans strain from a school or community lab source.
• Stereomicroscope or dissecting microscope.
• Micropipettes with tips.
• Small Petri dishes or assay plates.
• Digital kitchen scale with 0.1 g accuracy.
• Permanent marker for plate labeling.
• Timer or stopwatch.
• Temperature-stable storage box or drawer for plates.
• Distilled water.
• Food-grade sodium benzoate.
• BHT from a chemistry supply source approved by your lab.
• Odor source for chemotaxis testing, chosen with your mentor or teacher.
• Spreadsheet software for data entry.

Advanced Materials

• Incubator with controlled temperature for worm culture.
• Worm picking tool or platinum wire pick.
• Hemocytometer or imaging setup for estimating worm density.
• Stereo microscope with camera attachment.
• Fluorescence microscope if you plan to compare reporter strains.
• RNA extraction kit if your lab extends the project to expression validation.
• qPCR system for follow-up gene expression work.
• High-quality odorant standards for controlled chemotaxis assays.
• CeNGEN public dataset access through a computer with internet.
• Statistical software for dose-response and mixed-effects analysis.

Software & Tools

• Google Sheets: Organizes assay counts, calculates chemotaxis indices, and keeps replicate records clean.
• ImageJ: Measures plate zones or tracks worm positions from photos if you image each assay.
• R: Fits dose-response curves, runs statistics, and makes publication-style graphs.
• Python: Helps clean data, automate plots, and compare behavior with public expression tables.
• PubMed: Finds review articles and original papers on C. elegans olfaction, preservatives, and AWC neurons.

Experiment Steps

1. Define the exact behavior you will measure, such as chemotaxis index, choice ratio, or latency to enter an odor zone.
2. Select one odor cue, one preservative, and one worm stage so your first dataset stays focused.
3. Design controls that separate preservative effects from plate, solvent, and handling effects.
4. Plan a dose series that can reveal both weak and strong behavioral changes instead of just one comparison.
5. Build a data sheet before you start so each replicate records genotype, age, condition, and trial order the same way.
6. Match your behavior results with CeNGEN expression data to identify candidate sensory-neuron gene modules that may explain the pattern.

Common Pitfalls

• Using worms of mixed age, which can blur the effect of the preservative on chemotaxis.
• Letting odor spots spread unevenly across plates, which makes the choice zone hard to compare between trials.
• Mixing up solvent effects with preservative effects, which can create a fake signal.
• Counting worms before they settle into the assay, which inflates random movement as true attraction.
• Ignoring plate drying and humidity differences, which can change worm movement and distort the dose-response curve.

What Makes This Competitive

A strong version of this project does more than report one positive or negative effect. You can compare multiple doses, use clean controls, and analyze the data with a real dose-response model. The project gets stronger if you connect behavior to CeNGEN in a way that predicts a specific neuron pathway or gene module, then test whether the behavior follows that prediction. Careful replication and a clear statistical plan matter a lot here.

Project Variations

• Test whether the same preservatives affect attraction to different odor cues, not just one.
• Compare wild-type worms with a sensory mutant to see whether the effect depends on AWC-related signaling.
• Use public RNA-seq data only, and build a prediction model for which chemosensory genes should shift first.

Learn More

• CeNGEN: Search the CeNGEN portal and related papers for single-neuron gene expression data in C. elegans.
• WormBook: Search for review chapters on C. elegans chemotaxis, sensory neurons, and behavior.
• PubMed: Search review articles on C. elegans olfaction, AWC neurons, and preservative toxicology.
• NIH NCBI Gene: Look up worm genes connected to sensory signaling and receptor pathways.
• MIT OpenCourseWare: Search for introductory genetics, molecular biology, or data analysis course materials that help you read papers and analyze results.