Determining Phage Titer

1. Microwave flask of Top Agar (LB + 0.8% agar) to melt. Allow to cool until handleable, then prepare 4 ml aliquots in small test tubes for as many samples as you will be handling. Place tubes in a heat block set at 55-60°C.
2. Prepare dilutions of the phage stock in LB. Typically a dilution series from 10⁰ to 10¹⁰ in 10² increments will give one plate with a countable number of plaques. This can be easily prepared by making 1.7 ml Eppendorf tubes with 990 µl LB and transferring 10 µl from the higher stock, mixing, and transferring to the next sample.
3. Combine 100 µl of exponentially growing host cells and 100 µl of phage dilution. Incubate unshaken at 37°C for 30 minutes.
4. Add each sample to the top agar aliquot. Mix by pipetting up and down to avoid bubbles. Pour entire contents of test tube on top of an LB plate.

-- Main.ColinBrown - 14 Dec 2017