Rival bacterial colonies create a toxic “no-man’s-land” between them when they come too close to each other.
Image Source: PopSci, originally by Eshel Ben-Jacob.
I’d really be interested in seeing what the effect of adding another rival colony to one of the ends would be. Would a peace sign of buffer zone appear? After a few generations, would they start encroaching on the zone as they established resistance? Bacterial evolution is fun!