Chemotaxis and Band Formation of Escherichia Coli Studied by Light Scattering

Abstract

The phenomenon that certain motile bacteria move toward chemicals that aid their survival and away from chemicals that are harmful, is called “chemotaxis”. For instance, bacteria are attracted by nutritious sugars and amino acids, and repelled by phenol and their own excretory products such as acids and alcohols. The macroscopic aspects of bacterial chemotaxis have been known ever since the end of the 19th century, through the work of Engelmann (1) and Pfeffer (2). In 1966, Adler (3) revived the study using modern microbiology techniques. Subsequently, Berg and Brown (4) introduced the tracking microscope, and MacNab and Koshland (5) developed the temporal gradient apparatus. These efforts combined with other genetic analyses provide a detailed microscopic picture of bacterial chemotaxis. Escherichia coli and Salmonella typhimurium were commonly chosen for study because vast knowledge of their biochemistry and genetics exists. We have chosen E. coli (wild type K12) as a model system because its light scattering properties have been extensively investigated by our group during the last ten years (6,7,8).