Bioforming

From Memory Alpha, the free Star Trek reference.

Bioforming was a process that involved the transformation of an individual's physiology at a cellular level. Once bioformed, an individual could live in environments that would otherwise be deadly to their species. However, they could no longer tolerate their natural environment. In this sense, it was the opposite of terraforming. (VOY: "Demon")

In 2269, Kirk and Spock also experienced a type of bioforming on Argo, rendering them unable to breathe out of water. (TAS: "The Ambergris Element")

In 2374, Tom Paris and Harry Kim were diagnosed by The Doctor as having been bioformed on a Class Y planet in the Vaskan sector of the Delta Quadrant. (VOY: "Demon")