======Culturing Bacteria======


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**Alternative titles:** Growing Bacteria in Petri Dishes
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====Summary====                   
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====Procedure====  
  -Prepare nutrient agar by mixing agar powder with hot water and boiling until fully dissolved.
  -Pour the warm agar into Petri dishes, cover loosely, and allow it to cool and solidify.
  -Use a clean cotton swab dampened with water to collect bacteria from a chosen surface (hands, phone, keyboard, door handle, etc.).
  -Lightly streak or draw a squiggle on the agar surface with the swab, then replace the lid.
  -Label the dish with the date and sample source.
  -Optionally, place a drop of hand sanitizer on part of the streak as a test of antibacterial effectiveness.
  -Seal each dish in a zipper-lock bag and store upside down in a warm, dark place.
  -Observe colonies forming over several days, noting color, shape, and number.
  -Dispose of sealed dishes safely by adding bleach to the bags before throwing them in the trash.



====Links==== 
Growing Bacteria - Petri Dish - Sick Science!: 
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Homemade Petri Dish - Growing Bacteria at Home - The Sci Guys: 
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📄 Growing Bacteria in Petri Dishes - Steve Spangler: [[https://stevespangler.com/experiments/growing-bacteria/]]\\

📄 Exploring Germs and Bacteria at Home (DIY Agar Petri Dishes) - Astra Zeneca: [[https://www.astrazeneca.com/content/dam/az/media-centre-docs/article_files/articles-2020/11229%20-%20AZ-USASEF-Agar-Experiment-v7-STEM-Day-Version-GY-FH.pdf]]\\

====Variations====
  *Test different surfaces such as sinks, desks, toys, or skin.
  *Compare the effectiveness of different antibacterial products (hand sanitizers, wipes, soaps).
  *Record and compare colony growth over time using photos or drawings.



====Safety Precautions====
  *Do not open Petri dishes once growth begins—bacteria colonies can be harmful.
  *Do not allow students to get samples from anywhere in a toilet or bathroom.
  *Wear gloves if handling dishes and keep cuts covered.
  *Work under adult supervision, especially when boiling agar.
  *Dispose of dishes by sealing in bags with bleach; never reuse dishes for food.
  *Wash hands thoroughly after completing the experiment.





====Questions to Consider====
  *Which surfaces grew the most bacteria? Why? (Frequently touched surfaces harbor more microbes.)
  *What differences did you see in colony color, size, or shape? (They indicate different species of bacteria or fungi.)
  *How effective was the antibacterial product you tested? (Look for “kill zones” with little or no growth.)
  *Why is it important to keep the Petri dishes sealed? (To prevent harmful exposure to growing microbes.)
  *What does this experiment reveal about the importance of hand washing? (That our hands spread many invisible microbes.)