Where can we find bacteria How can you
Where can we find bacteria?
How can you find bacteria? • You can’t see it, so how do you find it? • Under the right conditions, bacteria grows very fast, exponentially • Some bacteria populations can double every 10 minutes • Bacteria grow in colonies – a colony is a visible mass of bacterial growth on solid medium that developed from 1 or a few cells • A colony can contain millions of cells • We can find bacteria by growing it in the right conditions until it is visible to the human eye
Growing/culturing bacteria • Conditions – temperature, light • Agar – source of nutrients for growth – From Malay word “agar-agar” meaning jelly – Gelatinous substance made from seaweed – Ingredient used in Japanese desserts
Lab Today • We’ll look for bacteria around the classroom and school • Track your cultures • Infer good conditions for bacterial growth
How to Sample Bacteria 2 Samples 3 Samples 4 Samples • Get a Petri dish • With a marker, divide it into 2, 3, or 4 equal parts
How to Sample Bacteria • Write on the bottom side (side with the agar) • Write small and around the edge so you can see the bacteria growing later • Decide where you will sample and label your Petri dish accordingly
How to Sample Bacteria • Get a sterile swab – don’t touch the cotton end • Swab the area to be tested • Open your Petri dish carefully and swab the cotton in the specified area on the agar • Close the Petri dish quickly • Get a new swab for each sample • When done, close the Petri dish and use scotch tape to seal the sides • Put the Petri dish upside down in a dark, warm place
Photo Credits • Slide 1 (Title): http: //www. norcalblogs. com/ and http: //biology. clc. uc. edu/Fankhauser/Labs/Microbiology/Coliform_assays /Plates_with_Colonies/Ohio_River_0. 2 m. L_Ma. C_P 8011311. jpg • Slide 3: http: //upload. wikimedia. org/wikipedia/commons/6/6 a/Agar_Plate. jpg and masak-masak. blogspot. com/ 2007_09_01_archive. html • Slide 5: http: //www 3. moe. edu. sg/edumall/tl/digital_resources/biology/images/pl astic_petri_dish. jpg • Slide 6: http: //upload. wikimedia. org/wikipedia/commons/6/6 a/Agar_Plate. jpg
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