INSTABILITY OF WAVES FORMED BY MOTILE BACTERIA

Many motile chemotactic bacteria (for instance, Escherichia coli) inoc ulated at some point in a semisolid nutrient medium can form circular expanding population waves. The formation of these motile structures i s due to chemotaxis. The circular waves originate from an expanding ba cterial lawn (a parent population). The regular shape of these waves r esults from the isotropic distribution of freely diffusible nutrient m olecules which are also attractants. In this paper we show that the re gular shape of the bacterial population waves can be spontaneously dis turbed. As this takes place arc-shaped population waves ('bursts') are formed. It was found that initially the mean length of the cells form ing the bursts was greater than that of the parent cell population. Bu t then it decreased resulting in a value characteristic of the parent population.