1 A do-it-yourself approach for basic basement steps starts around $250-$350 for materials, and takes about 3-4 hours. 2  That's with standard lumber, such as pine; costs can go much higher with more expensive wood, such as oak.
Pour enough melted agar into each sterile plastic petri dish to cover the bottom - about 1/8 to 1/4 deep. Replace the lid immediately. Place agar plates on a counter top to cool and set. Agar medium will set like stiff gelatin at room temperature. The agar medium is now ready for storage or use.
Agar is a gelatinous medium that provides nutrients and a stable, controlled environment for bacteria growth. Most bacteria will grow well using nutrient agar, but some more fastidious bacteria prefer tryptic soy agar. To prepare agar plates, just heat agar and pour it into a sterile petri dish. Swab along any surface to test (your mouth, the bathroom counter, etc.) and then lightly smear in a zig-zag pattern on the surface of the agar plates. Signs of bacteria growth should show within 1-2 weeks. Getting started: