Bacteria-based science projects offer a variety of interesting topics for students to investigate and present at science fairs. Bacteria can be grown in simple petri dishes filled with agar or in water and don't require a lot of expensive equipment, making them an excellent choice for science projects.
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Bacteria exhibit a great deal of diversity in the way they grow, both in the speed of growth and the different shapes, colours and growth patterns of their colonies. Students can examine bacterial diversity by swabbing potential sources of bacteria and growing the bacteria from each source in a separate petri dish filled with basic agar, a seaweed-based gel. Potential sources of bacteria include doorknobs, light switches, toilets, sinks, refrigerators, human hands, pets' mouths, bird baths and more--the possible sources are as varied as the bacteria they host.
Household cleaners, antibiotic soaps, hand sanitisers, mouthwash and antibiotics inhibit growth of bacteria and offer an opportunity for student exploration. Students can swab surfaces, such as a bathroom sink, to collect bacteria and use the swab to spread the bacteria onto the surface of a petri dish full of agar. Students then cut or hole-punch an absorbent blotter or piece of construction paper to create sensitivity squares or disks and soak each one in a growth inhibitor, such as Lysol or Listerine. Students carefully place the disks onto the surface of the bacteria-inoculated petri dish and allow the bacteria to grow. They measure the bacteria-free "zone of inhibition" around each growth inhibitor and compare the effectiveness of each one.
Environmental conditions, whether natural or the result of human activities, can promote bacterial growth and provide an interesting topic for student exploration. Students can examine growth promoting activities by swabbing surfaces to collect bacteria and growing the bacteria in agar-filled petri dishes. They can then set up different conditions under which bacteria can grow to determine which promotes the fastest growth. For example, students may investigate whether refilling water bottles for several days without washing them increases bacteria growth or study how important their chores are--do more bacteria really grow in the sink or refrigerator if it isn't cleaned every week?
Commercial test kits can quantify the amount of bacteria present in a sample. Using such kits, students can collect water samples from various natural sources and test hypotheses about conditions that promote or inhibit growth. For example, retention ponds that receive a lot of runoff from fertilisers or additional nutrients from pet or livestock faeces may host greater quantities of bacteria than more pristine natural water bodies. Stagnant swamps may host greater quantities of bacteria than flowing streams.
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