Researchers Create Invisible Ink From Engineered Bacteria

By seeding sheets of what look like paper with encrypted patterns of bacteria engineered to glow in certain conditions, researchers have developed an invisible ink for the biotech age.

Among the potential uses are secret, forgery-resistant bacterial barcodes and watermarks, though imagination soon arrives at more entertaining possibilities.
“Obviously, the secret agent kind of application jumps out,” said chemist David Walt of Tufts University, who developed the system with fellow Tufts chemist Manuel Palacios. “Somebody embedded in an environment where they need to get a message out but don’t want to be caught.”