Bacteria can paint with light, thanks to genetic engineering By Ryan CrossMay. 22, 2017 , 11:00 AM Nope. You’re not looking at a Bob Ross still life. This faintly colored image was “painted” by bacteria (Escherichia coli) that produce colored pigments in response to light. Scientists designed the bacteria by adding 18 new genes to their genetic circuitry, including thousands of DNA bases that code for light sensor proteins that respond to red, green, or blue light. Exposure to the light makes the bacteria turn on a gene that kicks off a chemical reaction, producing a corresponding red, green, or blue pigment. Other genes act like circuit breakers to keep the system from overloading. The paint-by-light images were produced by mixing the bacteria into a gel on a petri dish and placing them in an incubator exposed to projector or laser light. Using this setup, scientists recreated the Massachusetts Institute of Technology logo, Super Mario, a tiled pattern of lizards, and a pile of fruit (above), they report today in Nature Chemical Biology. Although the art is unlikely to be displayed alongside works by Van Gogh or Monet, the genetically engineered bacteria could have other practical applications. The scientists say their light-responsive circuit could help control the flux of metabolic pathways in vats of microbes used to produce pharmaceuticals or industrial chemicals, by turning on and off in response to red, green, and blue light—a veritable bacterial disco.