Possible mechanisms of the formation of structures in bacterial populations consisting of motile cells

The formation of fixed and moving structures was studied in Escherichia coli populations. The moving and fixed structures were shown to be formed only by bacteria with a taxis system. The moving structures caused an uneven distribution of the substrate concentration. Bacterial growth on agar with the unevenly distributed substrate led to the appearance of fixed structures. Mechanisms responsible for the formation of bacterial structures remain obscure.