Individual bacterial cells have short memories. But groups of bacteria can develop a collective memory that can increase their tolerance to stress. This has been demonstrated experimentally for the first time in a study by Eawag and ETH Zurich scientists published in PNAS.
Bacteria exposed to a moderate concentration of salt survive subsequent exposure to a higher concentration better than if there is no warning event. In populations exposed to a warning event, survival rates upon a second exposure two hours after the warning are higher than in populations not previously exposed. Firstly, salt stress causes a delay in cell division, leading to synchronization of cell cycles; secondly, survival probability depends on the individual bacterial cell’s position in the cell cycle at the time of the second exposure.