Final answer:
The last step in an aseptic transfer from a solid medium is to sterilize the inoculating tool, typically by flaming the inoculating loop, to prevent any contamination after the transfer.
Step-by-step explanation:
The last step in an aseptic transfer from a solid medium typically involves the proper handling and sterilization of the inoculating tool after the transfer has been made. After transferring the bacterial sample using a sterilized inoculating loop, you would flame the loop to sterilize it once again to ensure that no contamination occurs post-transfer.
This flaming process, done by holding the metal loop in a Bunsen burner flame until it is red hot, destroys any remaining bacteria and prevents them from spreading to other surfaces or mediums. It is crucial that this step be done before placing the loop down, as it signifies the completion of the aseptic transfer.
The LAST step in an aseptic transfer from a solid medium is to recap or close the container to prevent contamination. This is done to maintain the sterility of the transferred material and avoid introducing any external contaminants.