Resistance is futile. The basic setup is to use added light-switchable genes to control a synthetic genetic circuit in yeast cells. The problem with synthetic genetic circuits is that they often misbehave due to the messiness of biology. By connecting the output of the genetic circuit to production of a reporter protein that fluoresces and having a light-sensitive protein control the input, they could get an external computer to "tune" the cells in a feedback loop. Applications in beer, wine and ethanol manufacture come to mind....