Problem-solving bacteria crack sudoku - tech - 16 November 2010 - New Scientist

Problem-solving bacteria crack sudoku: The team begin with 16 types of E. coli, each colony assigned a distinct genetic identity depending on which square it occupied within a four-by-four sudoku grid. The bacteria can also express one of four colours to represent the numerical value of their square. As with any sudoku puzzle, a small number of the grid squares are given a value from the beginning by encouraging the bacteria in these squares to differentiate and take on one of the four colours.

These bacteria then use RNA recombinases packaged in viruses to send information about their location in the grid – and their colour value – to the undifferentiated bacteria in "unsolved" grid squares. The E. coli are "programmed" to accept RNA only from cells in the same row, column or block as themselves. The genetic information stored in the viral messages forbids the receiving bacteria from differentiating into the same colour as the transmitting bacteria, so by a process of elimination the undifferentiated cells establish which colour to adopt to "solve" the grid.