_Update: Keep your bacteria in the dark. I had been doing this without meaning to, and was confused to hear a fellow microbiologist growing a derivative of my cultures in her lab and getting no glow. When she grew them in the dark, they glowed again! Brief exposures have no effect. It's the prevailing light conditions that seem to decide whether to stay active. This may be due to the light breaking down the little peptide the bacteria use to detect whether there are enough of them to glow meaningfully, or it might be a deliberate evolutionary adaptation.
Update: The links to these files have always been precarious, sorry.. I've just re-uploaded the two main files, and soon I'll be reworking them into my “biohacking protocols” repository on Github in Markdown format with separate images. Enjoy! Life is, as ever these days, quite busy! I have two trips coming up, one to Ignite in Dublin and one to the Newcastle Maker Faire (where Brian Degger of Transitlab.org and I will be hosting a little workshop on a few DIYbio experiments and fun stuff).