It all comes back to iron, one of the most abundant elements on Earth. Singular and free-floating bacteria have varying levels of iron. Scientists observed that bacterial cells with lower levels of iron were better swarmers. In contrast, bacteria that formed biofilms, dense, sticky mats of bacteria on solid surfaces, had high levels of iron in their cells. Bacteria with antibiotic tolerance also had balanced levels of iron. These iron memories persist for at least four generations and disappear by the seventh generation.
Seventh Generation, you say