Argonne researchers corral E. coli

It is not often that E. coli bacteria are compared to beef cattle, but what if there was a way to corral them away from other microrganisms? Such has been the effort of various researchers at the Argonne National Laboratory and other facilities, who have developed a method of concentrating, manipulating, and separating a wide class of swimming bacteria. The device is said to have enormous applications in biotechnology and biomedical engineering, including use in miniaturized medical diagnostic kits and bioanalysis. “Unlike traditional centrifuging techniques, the new approach allows selective concentration of healthy cells,” said Dr. Andrey Sokolov.

How it works: The technique begins with the transmission of a small electric current through a thin film sample cell containing a colony of bacteria. The current produces electrolysis that changes the local pH level in the vicinity of the electrodes. The bacteria, uncomfortable with the changes in pH, swim away from the electrodes and towrads areas of their favored pH level. Since only living bacteria respond to the pH stimulation, the approach easily separates living and dead cells or bacteria with different motility.

Those interested in the more advanced study of hydronamics will be interested in some implications suggested by the researchers, which we admit are beyond our scientific competence to judge. “Research findings uncovered the explanation for the long-standing fundamental questions on the properties of collective and organized motion in the systems of interacting self-moving objects … Our results provide strong evidence for the pure hydrodynamic origin of collective swimming, rather than chemotactic mechanisms of pattern formation when microorganisms just follow gradients of a certain chemical, such as nutrient, oxygen, or other.”