Bacterial siblings avoid each other by starving, not by signaling or fighting.

When identical bacterial colonies grow near each other in soft gel, they mysteriously avoid touching. Instead, they leave sharp, clear lines between themselves. Scientists do not fully understand how microscopic behaviors cause these large-scale patterns. To solve this, researchers studied the common pathogen Pseudomonas aeruginosa using density measurements and a biophysical model. They discovered that the bacteria do not kill each other, compress the gel, or use cell-to-cell communication called quorum sensing. Instead, colonies simply eat up the local food between them. As food drops, the bacteria slow down and stop moving. This feedback between growing and moving halts the colonies before they meet. The starting amount of nutrients sets how strongly they avoid each other.

Why it matters

This matters because it changes how we think bacterial colonies interact. Instead of assuming chemical communication or warfare, the key factor is simple nutrient competition. This could help predict how bacteria spread in infections or in soil, and design microbial communities for biotech.

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