Microbial Colonization on Different Surfaces

ISEF Category: Microbiology

Subcategory: Bacteriology  ·  Difficulty: Advanced  ·  Setup: University Lab  ·  Time: Full Year

The Hook

Some surfaces are quieter than others, at least for bacteria. Copper can knock down microbes fast, while plastic can act like a long stay hotel. If you compare several materials side by side, you can turn that idea into real survival data. That means you can test more than which surface looks clean, you can test which one helps microbes persist.

What Is It?

This project asks how well bacteria survive and colonize different surface materials over time. Colonization means the cells stick, settle in, and keep growing or surviving on a surface. You are not just checking whether bacteria are present. You are comparing how fast they fade away, and whether some surfaces help them hang on longer.

Think of each material like a different kind of parking lot. Copper and brass are rough places for bacteria to stay alive. Stainless steel and plastic may be easier to persist on. An antimicrobial-coated fabric adds another twist, because the coating is supposed to lower survival in a way you can measure with colony-forming units, or CFU, which count living cells that can still grow on plates.

The Weibull survival fit is the math part of the project. It helps you describe how survival changes over time instead of just comparing one time point. That makes your results stronger, because you can compare the whole trend for each material, not just the final score.

Why This Is a Good Topic

This is a strong science fair topic because you can measure a clear outcome, living bacteria on each surface, and compare it across materials that matter in daily life. It connects to infection control, cleaning, food safety, and hospital design. You can learn surface sterilization logic, sterile technique, CFU counting, and basic survival curve analysis. You also have room to ask a real research question instead of repeating a textbook demo.

Research Questions

• How does surface material change CFU recovery from Micrococcus luteus over 14 days?
• How does surface material change CFU recovery from B. subtilis over 14 days?
• What is the effect of humidity on bacterial survival on copper, brass, stainless steel, plastic, and antimicrobial-coated fabric?
• To what extent do the two species differ in their survival curves on the same surface material?
• Which surface shows the fastest early drop in CFU for both species?
• How does the Weibull survival parameter differ across surface materials?
• What is the effect of repeated handling or cleaning on bacterial persistence on each material?

Basic Materials

• Sterile swabs with transport medium.
• Prepared coupon samples of copper, brass, stainless steel, plastic, and antimicrobial-coated fabric.
• Sealed humidity box or controlled chamber.
• Hygrometer and thermometer.
• Sterile Petri dishes and agar plates approved by your lab.
• Micropipettes and sterile tips.
• Digital balance for sample tracking.
• Permanent marker and labeled sample trays.
• Disinfectant approved by your lab safety plan.
• Gloves, lab coat, and eye protection.

Advanced Materials

• Pure culture stocks of Micrococcus luteus and B. subtilis.
• Biosafety-approved incubator.
• Class II biosafety cabinet or approved sterile work area.
• Autoclave or validated sterilization access.
• Colony counter or imaging setup for plate counting.
• Environmental chamber with humidity control.
• Surface roughness or contact-angle tools, if available.
• Replicate coupon sets with standardized finish.
• Data loggers for humidity and temperature.
• Reference strain documentation and lab-approved media.

Software & Tools

• R: Fits Weibull survival models and compares survival curves across materials.
• Python: Cleans CFU data, graphs time trends, and checks model fits.
• ImageJ: Measures colony counts from plate images when manual counting is hard to standardize.
• GraphPad Prism: Plots survival data and runs common statistical tests if your lab has access.
• NIH PubMed: Helps you find review articles on surface survival, biofilms, and antimicrobial materials.

Experiment Steps

1. Define whether you are testing initial attachment, long-term survival, or both, so your outcome matches your question.
2. Choose one bacterial species comparison plan and decide how many replicates each surface needs.
3. Standardize the surface coupons so texture, size, and cleaning history do not confound the result.
4. Plan a sampling schedule that captures both early loss and later persistence across the 14-day window.
5. Build a data analysis plan before you start, including how you will convert CFU counts into survival curves and fit a Weibull model.
6. Set controls for humidity, inoculum consistency, and recovery efficiency so surface effects are easier to trust.

Common Pitfalls

• Using surface pieces with different roughness or coating quality, which makes material effects impossible to separate from manufacturing noise.
• Swabbing each coupon with slightly different pressure or area coverage, which changes CFU recovery more than the surface itself.
• Letting humidity drift inside the chamber, which alters survival and ruins comparisons across the 14-day run.
• Counting only obvious colonies and missing crowded plates, which compresses the survival curve and hides real differences.
• Mixing up species or time points during plate labeling, which can make one material look better or worse by mistake.

What Makes This Competitive

A competitive version of this project does more than rank surfaces. It controls the coupon properties, uses enough replicates to support modeling, and compares survival trends with a real fit, not just raw counts. You can raise the level by testing two species with different cell wall traits, then asking whether one material behaves differently across them. Strong statistical analysis and careful recovery controls matter as much as the biology.

Project Variations

• Test the same surface set with a third species that makes spores or pigments to see whether cell type changes survival patterns.
• Swap humidity for a dry storage setup to compare how moisture changes surface persistence.
• Add a surface-roughness or contact-angle measure to see whether physical texture predicts CFU survival better than material name alone.

Learn More

• NIH PubMed: Search for review articles on bacterial survival on surfaces, biofilms, and antimicrobial materials.
• NCBI Bookshelf: Find free textbook chapters on microbiology methods, bacterial growth, and survival analysis basics.
• CDC laboratory biosafety resources: Review safe handling guidance and general biosafety concepts for student research.
• NOAA National Weather Service climate data: Use local humidity and temperature context when you discuss environmental factors.
• MIT OpenCourseWare: Look for introductory microbiology or biological statistics lectures that help with experimental design and data analysis.