Tutorials/Agar/Storing Cultures

Once you have a clean, strong culture, keep a copy safe. Storage gives you a backup when a grow contaminates, a clean starting point when a working culture weakens, and something to share with other members.

Good practice is to keep a master culture in long-term storage and a separate working culture you actually use. Never start a grow from the master directly; make a working copy from it instead.

Storage methods

Method	How long	Effort
Spore prints	Years	Low
Agar plates in the fridge	1–3 months	Low
Liquid culture in the fridge	Several months	Low
Agar slants in the fridge	6–12 months, sometimes longer	Medium
Agar plugs in sterile water	A year or more	Medium

Agar slants

A slant is a test tube partly filled with agar that was left to set at an angle, giving a long sloped surface. The small opening and tight cap make it far less prone to drying out and contamination than a plate.

Making them

1. Use screw-cap culture tubes, glass or autoclavable plastic. Loosen the caps a quarter turn.
2. Fill each tube about one-third with hot, liquid agar (a slightly firmer recipe, with a bit more agar powder, holds up better).
3. Pressure cook upright in a jar or rack.
4. While the agar is still liquid, lay the tubes down propped at an angle so the agar sets as a long slope. Tighten caps once cool.

Inoculating them

In a still air box or flow hood, transfer a small wedge from the leading edge of a clean plate onto the slope. Let it grow at room temperature until it covers most of the surface, then move it to the fridge.

Agar plugs in water

This method keeps cultures alive for a long time with almost no attention.

1. Fill small vials or tubes with distilled water and pressure cook them.
2. Cut several small cubes of colonized agar from a clean plate and drop them into the water.
3. Cap tightly, wrap the cap with Parafilm, and store at room temperature or in the fridge.

To revive, fish out a cube with a sterile tool and set it on a fresh plate.

Storage tips

• Keep cultures at about 35–40°F (2–4°C). Don't freeze them unless you've prepared them specifically for freezing.
• Some warm-weather species don't tolerate cold storage well. If a species struggles to restart after the fridge, keep its backups at cool room temperature instead.
• Seal plates with Parafilm and store them upside down in a zip bag.
• Label everything: strain, transfer number or source, and date.
• Refresh every 6–12 months: revive the stored culture on a fresh plate, confirm it's clean, and make new storage copies from it.
• When you revive any stored culture, let it warm to room temperature first and expect it to be sluggish for the first few days.