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Microbial Growth: Culturing Bacteria from Surfaces

Age Group

12-18 years old

Difficulty Level

Moderate

Duration

1-2 hours (plus time for bacterial growth)

What You'll Need

  • Agar plates (Petri dishes)

  • Sterile cotton swabs

  • Sterile saline solution or distilled water

  • Gloves

  • Disinfectant wipes

  • Incubator or warm area for bacterial growth

  • Safety goggles (optional)

What Will You Learn?

The purpose of this experiment is to explore microbial growth and diversity by culturing bacteria from different surfaces and observing their growth on agar plates.

Step-by-Step Instructions

Preparation: Prepare the agar plates according to the manufacturer's instructions. Allow them to cool and solidify before use.


  1. Collection of Samples: Put on gloves to prevent contamination. Use sterile cotton swabs moistened with sterile saline solution or distilled water to collect samples from surfaces like doorknobs, keyboards, or hands. Label the agar plates with the sample source.

  2. Inoculation: Gently streak the swab over the surface of the agar plate in a zigzag pattern. Close the plates and ensure they are sealed properly.

  3. Incubation: Place the agar plates in an incubator set to a suitable temperature for bacterial growth (usually around 37°C or 98.6°F). If an incubator is not available, find a warm area where the plates can be left undisturbed.

  4. Observation: Check the agar plates daily for bacterial growth. Observe the colonies' size, color, shape, and any other characteristics. Take notes or photographs to document the growth.

  5. Comparison: Compare the growth of bacteria from different samples and note any similarities or differences. Discuss possible reasons for variations in microbial growth.

  6. Safety Precautions: Dispose of used swabs and agar plates properly. Wash your hands thoroughly after completing the experiment and before touching any surfaces.

Safety First!

  • Handle agar plates and bacterial cultures with care to avoid contamination.

  • Wear gloves and safety goggles to prevent exposure to potentially harmful bacteria.

  • Disinfect surfaces and wash hands before and after collecting samples.

Watch The Experiment

Results Gallery

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FAQs

  • Why do we use agar in this experiment?Agar provides a nutrient-rich environment that supports bacterial growth, making it easier to observe and study different types of bacteria.

  • What safety precautions should be taken when handling bacterial cultures?Always wear gloves, never ingest or smell the cultures, and properly sterilize all materials after use.

  • How can bacterial growth be controlled on common surfaces?Regular cleaning and disinfection with appropriate products can help control bacterial growth on commonly used surfaces.

Download Your Experiment Guide

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  • "Growth of Mold on Bread"

  • "The Effectiveness of Hand Sanitizers"

Tags

Microbiology, Bacterial Culture, Microbial Diversity, Science Experiment, STEM Education, Teen Science, Laboratory Techniques

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