The circuit

Signal expression by mine cells (sender cells)

Mine colonies constitutively express the "mine-cell reporter” that reacts with one compund of the multi-substrate solution to produce a chromogenic product that indicates a mine colony. Addition of the multi-substrate turns the colony blue, indicating the mine and hence the game ends. At the same time, the mine colony is a sender module of OHHL. LuxI is expressed constitutevely and synthesizes the OHHL signaling molecules. This means that the mine continuously produces OHHL, allowing it to gradually diffuse radially out to neighboring colonies. The signaling molecule OHHL is processed by the receiver cells in the agar mine grid.

Figure 3: [OHHL] dependent information processing

Information processing by non-mine cells (receiver cells)
So what exactly happens with the expressed OHHL?

1. Receiver cells respond to low OHHL levels: If one mine cell is close to a non-mine colony and by OHHL diffusion takes place to reach the non-mine colony. Due to a highpass filter using the LuxR system in the non-mine colony,low concentrations of OHHL are detected and activate a reporter. Addition of the multi-substrate to this colony produces a salmon color, which indicates one mine is adjacent to the colony just played.
2. Receiver cells respond to high OHHL levels:If there are two or more mine colonies adjacent to a non-mine colony, a higher concentration of diffused OHHL will be processed by the receiver colony. The LuxR system works as a highpass filter again and induces the expression of another reporter to show that two or more mines surround the selected colony. Addition of the multi-substrate to this colony produces a magenta color that indicates that more than one mine is adjacent to this colony.
3. Receiver cells signal with no mines in their vicinity. If there is no mine adjacent to a non-mine colony, no OHHL is processed. Only the constitutive hydrolase is expressed, which on addition of the multi-substrate will give a yellow color. This indicates that there are no mines adjacent to this colony and the game can be continued.

Flagging
Remember what the flagging does in a traditional minesweeper game? Placing a flag on a mine prevents the mine to detonate. Flagging is possible in Colisweeper too. If the player is sure about a colony to be a mine, a second single substrate can be added on to this colony. Because all colonies express a constitutive reporter for flagging, a green colored product indicates a flagged colony. But remember, flagging does not reveal any information about mines in neighboring cells.

We thank our sponsors: