Final answer:
The first step in an aseptic transfer from a solid medium is flame-sterilizing the inoculating tool to prevent contamination before picking up a colony for transfer.
Step-by-step explanation:
The first step in an aseptic transfer from a solid medium is to flame-sterilize the inoculating tool such as a loop or needle, before picking up a colony. This step ensures that the tool is sterile and free of any unwanted microbes. Once the tool has been sterilized, it is then used to carefully pick up a single bacterial colony or a part of a colony from the surface of an agar plate for transfer.