How to Streak Bacteria on Agar Plates
Distinguish between a fresh plate and your bacterial or yeast sample.
- Hold plates up to a bright background, and pan back and forth watching the glare on the agar
- Bacteria looks like a cloudy film unevenly dispersed over the surface
- Your fresh plate should be almost clear with a slight tint.
Retrieve bacteria with inoculating loop
- Hold loop parallel to plate surface
- Gently glide over bacterial colonies trying to gather and group them on the loop.
*DO NOT PRESS TOO HARD OR LOOP WILL BREAK AGAR*
- A milky goo will be visible on the loop if performed correctly
Apply bacteria to fresh plate by spreading
- Hold loop with bacterial sample parallel to fresh plate
- Gently rub loop across surface spreading bacteria thinly throughout
- Flip loop on other side or even gently drag edges across plate if visible bacteria still needs to be delivered.
- You should be able to see the lines you made on the surface when you hold the plate like the test you did in Step 1.