Scientists at Tufts University have refined a method that allows people to send messages using fluorescent strains of Escherichia coli. There's enough color combinations to encode the entire alphabet, the numbers 0 to 9 and a few symbols.
The procedure, called steganography by printed arrays of microbes (SPAM), starts in the lab where the bacteria are arranged in color-coded messages and grown on a petri dish. The cultures are then transferred to a thin film that can be sent to someone else. The message is revealed when the recipient grows the bacteria in a fresh petri dish. And you can do so much more if you add in other genetic modifications.
According to research lead David Walt, scientists can create a self-destructing message by using fluorescent bacteria that lose their glow after a certain amount of time. Even antibiotic resistant strains can be used to add a security measure to a message. These strains require the recipient to add the right antibiotic to decode the message. If the wrong one is added, the resulting message would be gibberish.