Do video games change behavior? This question may be the subject of debate for years, but researchers have now shown the answer to be yes—for microorganism behavior, at least.

A research group led by Stanford bioengineering professor Ingmar Riedel-Kruse has developed several real video games, inspired by Pac-Man, PONG and other classics, starring live organisms. "The basic idea," explains Riedel-Kruse,"is to create games where a player has ability to interact with living matter during game play."

Riedel-Kruse is quick to point out that games reliant on real biology are far from new (consider horse polo, for example, which he notes could be considered "ancient biotechnology"). Nor are his games the first to employ real biological processes. But surely nobody has ever designed a game quite like PAC-mecium, a Pac-Man-inspired game featuring single-celled paramecia whose movement is controllable by human players.

The idea came to the scientist as he was reading about the history of video games, spurred around five decades ago by the rapid development of electronics and computing power. "Biotechnology is currently running through a similar revolution or exciting phase, so I thought since this other technology back then enabled games, why shouldn’t this new technology enable games as well?" The project is described this month in the journal Lab on a Chip.


PAC-mecium takes advantage of a sensory phenomenon called galvanotaxis, which causes paramecia to respond to external electrical fields by moving in the direction of a cathode. The protozoa move about in a fluid chamber outfitted with electrodes on each side, and a human player can apply electrical fields, using a handheld controller, to coax a swarm of the single-celled organisms in desired directions. A webcam captures the paramecia's movements, which are then displayed live on a computer screen.

Riedel-Kruse's team took things one step further by overlaying game-like graphics on the real-time video. In the place of PAC-dots are virtual yeasts, and rather than avoiding ghosts, the goal is to steer the paramecia clear of virtual zebrafish larvae.


In "Ciliaball," the object is to get the paramecia to score goals with a virtual soccer ball. Riedel-Kruse's group used the same basic set-up for this game as they did for PAC-mecium.


In "Microbash," inspired by the classic game "Breakout," the human player tries to steer paramecia toward a virtual ball that is bouncing around the screen. If a paramecium makes contact, the ball will bounce in the opposite direction of the contact. The object is to knock the ball into a group of bricks at the top of the screen. The bricks can be knocked away one at a time, and behind them is detailed illustration of a paramecium, which comes into full view once all the bricks are knocked away.


In addition to changes in electrical fields, paramecium also respond to chemical stimuli—a phenomenon called chemotaxis—which Riedel-Kruse employed to create an additional gaming platform. In this set-up, human players can control the release of chemicals from a tiny needle, setting the stage for a pinball-like game, and even a two-player competition inspired by "PONG."

Besides the paramecium-centric games, the group also developed a betting game featuring the polymerase chain reaction (PCR) as well as an "olfaction strategy game" that employs yeast. Although creating an enjoyable experience is part of the goal, Riedel-Kruse says his larger ambition is to find ways to make the games useful, perhaps in the context of science education, or even as tools for crowd-sourced research projects. "We are currently developing more robust games and we’d like to go to schools, or make the games available on the Internet," he says. And given the capabilities of modern biotechnology, "I think the time is ripe that we do these kinds of things."