Before you start
- Label the bottom of the plate (strain, date, initials).
Reagents and materials
Totals are for 4 plates (+10% extra). Per-plate amounts are in the middle column.
| Reagent | Per plate | Total |
|---|---|---|
| Agar plate (selective if needed) | 1 each | 1 each |
| Sterile loop or toothpickone per quadrant if disposable | 4 each | 4 each |
Equipment
- Inoculating loop and burner (or disposable loops)
- 37 °C incubator
Procedure
Tick steps as you go (saved in this browser). Steps with a clock have a built-in timer.
Pick inoculum
Touch a sterile loop to the culture, colony or the surface of a frozen glycerol stock (do not thaw it).
First quadrant
Streak back and forth over about a quarter of the plate.
Second quadrant
Sterilise or change the loop, cross into the first quadrant 2–3 times and streak a second quadrant.
Third and fourth quadrants
Repeat, each time dragging from the previous quadrant, to dilute the cells.
Incubate
Incubate inverted at 37 °C (or the organism’s temperature) for 16–24 h.
Pick colonies
Use well-separated single colonies for cultures; store plates at 4 °C for up to a few weeks.
Critical points
- Always work from a single colony to ensure a clonal population.
Troubleshooting
| Problem | What to check or change |
|---|---|
| No single colonies | Use less inoculum and change/sterilise the loop between quadrants. |
| Mixed colony types | Re-streak a single colony; check for contamination. |
Safety
Work at the biosafety level of the organism; flame or dispose of loops properly.
Further reading
- ASM Microbe Library: streak plate protocol.
This is a general starting-point protocol written for SolvesEverything. Follow your institution’s approved protocols, safety rules and manufacturers’ instructions, and optimise for your system. Spotted an error? Tell us.