Bacteria survive hostile stages using a variety of sophisticated strategies. Most techniques depend on the formation of communities and on a well-organized multicultural group-behavior. Stress might occur during successful colonization too, where siblings occupy the same niche and compete on the same resources. While survival strategies of individuals in the same colony are well-described, little is known about competitions between neighboring colonies of the same species. When food is depleted and space is limited, sibling Paenibacillus dendritiformis bacterial colonies exhibit a deadly competition; they mutually secrete a lethal protein, lysing cells at the interfaces between them. While some cells die, a signal induces a small proportion of the cells to switch from motile, rod-shaped cells, into robust but vegetative non-motile cocci. Unlike dormant spores, cocci replicate and thrive through the sibling rivalry. When overcrowding is reduced and nutrients are no longer limiting, the bacteria produce a signal that induces cocci to switch back to motile rods, allowing the population to spread. Genes encoding components of this phenotypic switching pathway are widespread among bacterial species, suggesting that this survival mechanism is not limited to P. dendritiformis.