Pour off the last rinse water and sterilise the tweezers by removing from the alcohol and passing through a bunsen flame. The alcohol will burn off. Allow the tweezers to cool for a few seconds. Pick up one of the root nodules and transfer to a drop of sterile water in a petri dish. This should have released the nitrogen fixing Rhizobium bacteria into the drop of sterile water.
Heat sterilise a microbiological loop by flaming for a few seconds to a cherry red colour.
Allow to cool for a few seconds. Repeat steps 8 and 9 for the other root nodules. Invert the agar plates before Incubating at 20 to 25oC for at least 3 to 5 days. If growing Rhizobium on YMA you should see gloopy pale coloured colonies. If you do a gram stain from these colonies and examine under the light microscope, you should have a gram negative rod-shaped organism.