Pattern and control in bacterial colony development.

As we learn more about bacterial life in the laboratory and in nature, we increasingly appreciate that they are highly sensitive and sophisticated organisms. One of the principal new insights has been the appreciation that bacteria are interactive and form organized, differentiated multicellular communities. Colonies produced on laboratory media by the standard research bacterium, Escherichia coli, are excellent examples. The organization of these colonies can be visualized in the microscope, by macrophotography, and by the use of special dyes and genetic engineering techniques to reveal patterns of differential gene expression. Observation of the dynamics of colony growth, and the response of colonies to experimental disruptions of normal development, indicate that control systems work to produce the regular patterns observed. The effects of obstacles and of other colonies on gene expression patterns indicate that non-linear responses to chemical gradients in the substrate play an important coordinating role in colony development.