It is part of the traditional lore of microbiology departments, handed down by word of mouth but largely unrecorded in the literature, that bacteria, isolated from the environment for their ability to perform particularly interesting metabolic functions, often show an infuriating instability. The usual version of the story is that a strain, originally obtained by selective enrichment on some esoteric compound as sole carbon source, could no longer grow on that compound after sitting on a slope for several months. In other versions, instability was a regular occurrence and part of a routine laboratory practice would be to reisolate the original strain from a selective medium. Occasionally a promising sequence of publications on a particularly interesting strain became abruptly terminated due to the failure to resuscitate it from its premature functional demise.