To estimate the initial number of colony-forming units in a mycangium, use the technique of serial dilution. See Database protocols for Isolations databse for how to accurately input this information into the database.
- Prepare two tubes per each sample, label them “0.1” and “0.01”, fill each with 500 ul of water or PBS.
- Suspend mycangium in the tube “0.1” and vortex.
- Plate 50 ul of the suspension on media. Record the plate as “0.1 dilution” in [PLATES].[note] in the Isolations database.
- Transfer 50 ul of the initial suspension to the second tube (“0.01”) and vortex.
- Plate 50 ul of the second suspension on second media plate, and record that plate as “0.01 dilution”.
- Plate 5 ul of the second suspension on a third plate, and record it as “0.001 dilution”.
Calculation of CFU count
Multiply the number of colonies on the plate by the inverse of the initial dilution factor.