Bacillus Seed Coating for Stress Tolerance

ISEF Category: Microbiology

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

The Hook

Seeds do not just grow on their own. The microbes on them can change how well a plant handles drought and salt. That means a tiny coating on a seed may affect leaf temperature, biomass, and stress tolerance. You can turn that into a real experiment.

What Is It?

This project tests whether coating seeds with Bacillus subtilis spores helps young plants cope with stress. Bacillus subtilis is a soil bacterium that can form spores, which are tough survival cells. Think of spores like a packed suitcase. They let the bacteria survive dry storage and wake up later when the seed gets wet.

When the bacterium helps a plant, it can do a few things. It may help roots grow better, change how the plant uses water, or help the plant handle salty soil. In a drought or salt stress setup, a healthier plant often keeps cooler leaves because it can move water more efficiently and keep stomata, the tiny pores on leaves, working better. That makes leaf temperature a useful proxy, or indirect clue, for stomatal conductance.

Why This Is a Good Topic

This is a strong science fair topic because you can change one clear variable, the Bacillus dose, and measure real outcomes like biomass and leaf temperature. The project connects to farming in dry or salty soils, which is a real-world problem with huge economic value. You can also build a clean dose-response study, which gives you room to use careful controls and stronger statistics than a simple before-and-after project.

Research Questions

• How does Bacillus subtilis seed-coating dose affect lettuce biomass under drought stress?
• What is the effect of Bacillus subtilis seed coating on radish leaf temperature under salt stress?
• Does a higher spore dose improve survival or growth more than a low dose in stressed potting mix?
• To what extent does the effect of Bacillus subtilis differ between lettuce and radish?
• Which stress condition, drought or salt, shows the largest growth benefit from seed coating?
• How does seed coating with Bacillus subtilis change the relationship between leaf temperature and biomass?

Basic Materials

• Lettuce seeds and radish seeds.
• Bacillus subtilis spore suspension or spores from a school-approved source.
• Potting mix with consistent composition.
• Small pots or cell trays with drainage.
• Digital kitchen scale with 0.1 g accuracy.
• Measuring cup or graduated cylinder.
• Watering bottle or squeeze bottle.
• Table salt for salinity treatment.
• Labels and waterproof marker.
• Smartphone with an infrared thermometer add-on or leaf-temperature camera attachment.
• Ruler or digital calipers.
• Drying rack or paper bags for biomass drying.
• Notebook or spreadsheet for data logging.

Advanced Materials

• Bacillus subtilis culture from a school-approved microbiology source.
• Sterile saline or buffer for spore handling.
• Spectrophotometer or hemocytometer for inoculum standardization.
• Autoclave or pressure sterilizer for media and waste handling.
• Growth chamber or controlled-environment bench.
• Infrared thermal camera with calibrated emissivity settings.
• Leaf porometer for direct stomatal-conductance measurements.
• Drying oven for constant-mass biomass measurements.
• Image analysis setup for leaf area measurement.
• Microbalance for fine mass differences.

Software & Tools

• Google Sheets: Organizes growth data, calculates means, and plots dose-response graphs.
• ImageJ: Measures leaf area and helps compare plant size across treatments.
• R or RStudio: Runs statistical tests and models treatment effects with clear graphs.
• NASA Image and Video Library: Provides background visuals and stress biology examples for presentation context.
• PubMed: Helps you find review articles and studies on Bacillus, plant growth promotion, and drought stress.

Experiment Steps

1. Define one plant species, one stress type, and one outcome you will measure first.
2. Set up treatment groups that separate dose effects from stress effects and include untreated controls.
3. Decide how you will standardize seed coating so each seed gets a comparable exposure.
4. Plan your measurement system for biomass and leaf temperature before you start growing plants.
5. Build a data table that tracks plant identity, treatment, growth stage, and final measurements.
6. Choose the statistics you will use to compare treatments and test for a dose-response pattern.

Common Pitfalls

• Using uneven seed coating, which makes some seeds get far more Bacillus than others.
• Letting soil moisture vary between pots, which hides whether the bacteria or watering caused the effect.
• Mixing up drought stress and salt stress, which makes the treatment question too vague.
• Measuring leaf temperature at different times of day, which changes the proxy even when plant health stays the same.
• Comparing fresh biomass only, which can blur real differences unless you also standardize drying and moisture.

What Makes This Competitive

A stronger version of this project would test a clean dose-response curve, not just treated versus untreated seeds. You can also compare lettuce and radish side by side, since different crops may respond in different ways. If you pair leaf-temperature data with biomass and proper controls, you get a more convincing story about plant water status. Strong entries often include careful statistics, replication, and a clear explanation of why one dose works best.

Project Variations

• Test Bacillus subtilis seed coating on one crop only, then compare drought stress across several soil moisture levels.
• Swap the leaf-temperature proxy for direct stomatal-conductance measurements if your school has a porometer.
• Compare Bacillus subtilis with another plant-growth-promoting microbe to see whether the effect is species-specific.

Learn More

• PubMed: Search for review articles on Bacillus subtilis, plant growth-promoting bacteria, drought stress, and salinity stress.
• NIH NCBI Bookshelf: Look for free textbook chapters on plant stress physiology and microbial interactions.
• USDA National Agricultural Library: Search for seed treatment, biocontrol, and plant-microbe research summaries.
• NOAA Climate.gov: Use background information on drought stress and water limitation in agriculture.
• NASA Earth Observatory: Find articles and images on drought, salinity, and crop stress in changing climates.
• MIT OpenCourseWare: Search biology and microbiology course materials for basic concepts in microbial physiology and plant responses.