OptoLac Tiger (IMAGE) Princeton University, Engineering School Caption Princeton University researchers invented a method for using light to turn on and off a mechanism in E. coli bacteria that is key to making the bacteria produce valuable chemicals. Here the genetic tool they invented, called OptoLac, was demonstrated by projecting light in the pattern of a tiger onto a petri dish, which caused only the bacteria exposed to the light to produce a green fluorescent protein. Credit Avalos Lab/Princeton University Usage Restrictions For non-commercial use License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.