According to a recent study published in the scientific journal ACS Synthetic Biology, a group of scientists have found a way to engineer a "genetic circuit" of E. coli that can solve a maze problem that functions in the same way as computer binary language — essentially, a biocomputer, made from E. coli. From the abstract:
We created six multi-input synthetic genetic AND gates, which distributed among six cell populations and organized in a single layer. Those cell populations in a mixed culture worked as a computational solver, which solved the chemically generated maze problems by expressing or not expressing four different fluorescent proteins. The three available "solutions" were visualized by glowing bacteria, and for the 13 "no solution" cases, no bacteria glowed. Thus, our system not only solved the maze problems but also showed the number of solvable and unsolvable problems. This work may have significance in cellular computation and synthetic biology.
The MIT Technology Review explained this process a bit more succinctly:
Getting E. coli to solve the maze problem involved some ingenuity. The bacteria didn't wander through a palace labyrinth of well-pruned hedges. Rather, the bacteria analyzed various maze configurations. The setup: one maze per test tube, with each maze generated by a different chemical concoction.
The chemical recipes were abstracted from a 2 × 2 grid representing the maze problem. The grid's top left square is the start of the maze, and the bottom right square is the destination. Each square on the grid can be either an open path or blocked, yielding 16 possible mazes.
Bagh and his colleagues mathematically translated this problem into a truth table composed of 1s and 0s, showing all possible maze configurations. Then they mapped those configurations onto 16 different concoctions of four chemicals. The presence or absence of each chemical corresponds to whether a particular square is open or blocked in the maze.
The team engineered multiple sets of E. coli with different genetic circuits that detected and analyzed those chemicals. Together, the mixed population of bacteria functions as a distributed computer; each of the various sets of cells perform part of the computation, processing the chemical information and solving the maze.
Distributed Computing with Engineered Bacteria and Its Application in Solving Chemically Generated 2 × 2 Maze Problems [Kathakali Sarkar, Saswata Chakraborty, Deepro Bonnerjee, and Sangram Bagh / ACS Synthetic Biology]
An E. coli biocomputer solves a maze by sharing the work [Siobhan Roberts / Technology Review]
Image: NIAID / Wikimedia Commons (CC-BY-SA 2.0)