This protocol is written for folks who are starting out phage work and don’t super care about getting the maximum yield (highest titer or concentration of phages). Once you carry out literature review, you might find facts about the phage of your interest. You may also do some preliminary experiments to determine what works best for your phage.

There are many ways to skin the cat grow your phages; the important thing is that you report the protocol that you ended up using for your published data.

Growth conditions

Growth media & temperature

• Rule of thumb is to use the growth media & temperature that you use for growing bacteria. Some phages grow better at certain temperatures.
• Ca²⁺ and Mg²⁺ are shown to be enhance binding of some phages to hosts. It may increase the phage yield if you add 10 mM MgSO₄ and 5 mM CaCl₂.

Phage stock to propagate

You can

• either start from a previous stock of the phage
• or, if you care about picking a single phage genotype for your experiment: make plaques and

Propagation media

• There are two main ways to propagate phages. Both generally work well for lab-adapted phages, with variable success in titering.

The actual protocol(s)

Propagation in liquid cultures - easier, requires less media prep

• Grow the bacterial cells to exponential phase in shaking culture flasks.
  • Some phages care about the host’s growth phase (e.g., exponential phage may be when maximum number of receptors are expressed), some don’t.
• Add 10-100 uL of phages (see “phage stock to propagate” above)

Propagation on solid media (Double Layer Agar method)

• Top agar: 0.3-0.75% agar in growth media
• Bottom agar: 1.5% agar in growth media (similar to agar plates that we pour for growing bacterial colonies)