Biology · Microbiology
Grow bacteria from everyday surfaces
Swab phones, door handles and washed hands onto agar and compare the colonies that grow.
- DifficultyIntermediate
- Estimated time2–7 days
- Budget₹250–₹500
- ClassClass 9–12
- Team2–3 people
- You needLab equipment required
Prerequisites: Idea of microorganisms
Original · by TechnifyedExperimentScience Fair ProjectLow costWell documented
Overview
Microbes are on every surface. Swabbing them onto nutrient agar and keeping the sealed plates warm lets each cell grow into a visible colony you can count.
Why build this?
It makes the invisible visible and gives hard numbers on whether handwashing and sanitiser work.
What you will learn
- How microbes are cultured
- Why sterile technique matters
- How to count and compare colonies
- Why cultures must never be opened
Skills you will use
Safety
- Treat every culture as if it could be harmful: keep dishes sealed, never open them once grown, and soak them in disinfectant before disposal. Wash hands after each session.
Materials and tools
- Agar plates (bought, or made with agar powder and stock)
- Sterile cotton swabs
- Tape and marker
- Warm dark place
- Bleach for disposal
Step-by-step roadmap
Start
You will finish with: a set of dated photos, colony counts and a ranking of surfaces.
- 1
Prerequisites
Know this first: idea of microorganisms. Then collect the 5 items in the materials list.
- 2
Learn
- How microbes are cultured
- Why sterile technique matters
- How to count and compare colonies
- Why cultures must never be opened
- 3
Plan
Write your question, your hypothesis and the one thing you will change. Draw the table you will fill in before you start.
- 4
Build
- Label plates: phone, door handle, unwashed hand, washed hand, sanitised hand, and an unopened control.
- Rub a damp sterile swab on each surface and streak it gently on its plate.
- Tape every plate shut and keep them upside down at room temperature.
- Photograph through the lids daily for five days without opening.
- Count the colonies on each plate.
- Soak the sealed plates in bleach solution before throwing them away.
- 5
Test
The control should stay clear; the washed-hand plate should show fewer colonies than the unwashed one.
- 6
Document
Record every reading with its unit, photograph the setup and draw a graph of the result. Report structure
- 7
Present
Explain the question, the method and the graph in two minutes; keep the setup ready to demonstrate. Presentation structure · Viva questions
- 8
Publish
Share the report and photos with your class, a science fair or your school magazine.
Expected outcome
A set of dated photos, colony counts and a ranking of surfaces.
Other versions of this project
Beginner version
Compare only unwashed and washed hands.
Advanced version
Compare soap, sanitiser and plain water for 5, 20 and 40 seconds of washing.
Research version
Survey ten identical surfaces across the school and analyse whether touch frequency predicts colony count.
Make this project better
- BasicCompare only unwashed and washed hands.
- This projectGrow bacteria from everyday surfaces
- AdvancedCompare soap, sanitiser and plain water for 5, 20 and 40 seconds of washing.
- ResearchSurvey ten identical surfaces across the school and analyse whether touch frequency predicts colony count.
Ways to do this project
Text marked "You write this" is a prompt for your own work; everything else is specific to this project.
- Problem
- Which everyday surface carries the most culturable microbes, and how much does handwashing reduce them?
- Hypothesis
- If hands are washed with soap for 20 seconds, then fewer colonies will grow than from unwashed hands.
- Variables
- Independent: surface or treatment. Dependent: number of colonies after five days. Controlled: swab method, agar, temperature, time
Materials and procedure are in Materials and the Roadmap.
Observation table
| Plate | Day 2 | Day 3 | Day 5 colonies | Notes on colour and shape |
|---|---|---|---|---|
- Graph
- Bar chart of colony count for each surface
- Results
- You write thisState what the graph shows in one or two sentences, with numbers.
- Conclusion
- You write thisSay whether the result supports your hypothesis and why you think so.
Display board
- Title and your name
- Question
- Hypothesis
- Materials
- Procedure (with photos)
- Data table and graph
- Conclusion
- What you would do next
Questions judges ask
- Why keep plates upside down?
- Why must plates stay sealed?
- Does each colony come from one cell?
- What would you change if you did this again?
- What was your biggest source of error, and how did you reduce it?
- Where is this idea used in real life?
- Research question
- Which everyday surface carries the most culturable microbes, and how much does handwashing reduce them?
- Hypothesis
- If hands are washed with soap for 20 seconds, then fewer colonies will grow than from unwashed hands.
- Variables
- Independent: surface or treatment. Dependent: number of colonies after five days. Controlled: swab method, agar, temperature, time
- Methodology
- Survey ten identical surfaces across the school and analyse whether touch frequency predicts colony count.
- Data collection
- You write thisSay what you will record, how many times, and how you will keep the records safe.
- Analysis
- Bar chart of colony count for each surface
- Limitations
- You write thisList what could have affected the result: small sample, instrument limits, things you could not control.
Literature review
Find five to eight sources (your textbook, review articles, reports) and note what each says about your question. Group them by idea, not one after another, and end with what is still not known.
References
List every source you used in one style throughout (author, year, title, where it was published, link and the date you opened it).
Working as a team
2–3 people. Suggested roles:
Report and presentation
Report structure
- Title and question
- Background: the science behind it
- Hypothesis
- Materials
- Method (steps, with a diagram or photo)
- Observations (table)
- Results (graph and calculation)
- Sources of error
- Conclusion
- What you would do next
- References
Presentation structure
- The question
- Why it matters
- The idea behind it
- Setup (photo)
- Method in three steps
- Results (one clear graph)
- What the result means
- Errors and limits
- Conclusion and next step
Viva questions
Try answering before you open each one.
Why keep plates upside down?
So condensation does not drip onto the agar and spread colonies.
Why must plates stay sealed?
Some of the microbes grown could be harmful in large numbers.
Does each colony come from one cell?
Usually from one cell or a small clump.
Why is there a control plate?
To show the agar itself was not contaminated.
Resources
Source and attribution
Original
Written by Technifyed. Free to use for your own school or college project; write the report in your own words. Added 1 Oct 2026.
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