Researchers develop technique for bacteria crowd control

Apr 17, 2007
Researchers develop technique for bacteria crowd control
Image illustrates swimming bacteria in a thin film.

A surprising technique to concentrate, manipulate, and separate a wide class of swimming bacteria has been identified through a collaboration between researchers at Argonne National Laboratory, Illinois Institute of technology, University of Arizona at Tucson, and Cambridge University, UK. This device could have enormous applications in biotechnology and biomedical engineering including use in miniaturized medical diagnostic kits and bioanalysis.

The technique is based on the transmission of tiny electric current in a very 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 ultimately congregate in the middle of the experimental cell. Concentrated bacteria form self-organized swirls and jets resembling vortices in vigorously stirred fluid.

The method, which is suitable for flagellated bacteria such as E.coli, Bacillus subtilis, among many others, relies on the ability of bacteria to swim toward areas of optimal pH level. The bacteria live in an environment of a specific pH level, so that an increase or decrease of pH stimulates the bacteria to avoid areas of non-comfortable pH and swim in the direction of pH gradient. The researchers used an electric current to create a controlled deviation of the pH levels from the bulk values. Since only living bacteria respond to the pH stimulation, using this method can separate living and dead cells or bacteria with different motility.

The device, capable to change the thickness of a film from 1mm to 1 micron (with accuracy of 5 percent) and control the position of electrodes, is intended to separate and concentrate small quantities of live /dead microorganisms in confined spaces. It can be used for the purposes of express bioanalysis, diagnostic, and identification of small bacterial samples, and separation sicken/live cells. A patent for the device is currently pending.

"Using this method, our research succeeded in dramatically increasing the concentration of microorganisms in tiny fluid drops and films. Unlike traditional centrifuging techniques, the new approach allows selective concentration of healthy cells," said Andrey Sokolov, Ph.D. student from Illinois Institute of Technology and contributor to the research.

In addition to the development of the device used in the experimentation, research findings uncovered the explanation for the long-standing fundamental question on the properties of collective and organized motion in the systems of interacting self-moving objects. Besides swimming bacteria, other examples include bird flocks, fish schools, motor proteins in living cell, and even swarms of communicating nano-robots.

"We have presented experimental studies of collective bacterial swimming in thin fluid films where the dynamics are essentially two-dimensional and the concentration can be adjusted continuously," explained Igor Aronson, physicists at Materials Science Division, Argonne National Laboratory. "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."

Source: Argonne National Laboratory

Explore further: Bulletproof nuclei? Stem cells exhibit unusual absorption property

add to favorites email to friend print save as pdf

Related Stories

Separating the good from the bad in bacteria

Oct 16, 2013

There are good bacteria and there are bad bacteria—and sometimes both coexist within the same species. Take, for instance, Pseudomonas aeruginosa, a microbe common in soil and water. This bacterium has been found to col ...

Recommended for you

Plants with dormant seeds give rise to more species

Apr 18, 2014

Seeds that sprout as soon as they're planted may be good news for a garden. But wild plants need to be more careful. In the wild, a plant whose seeds sprouted at the first warm spell or rainy day would risk disaster. More ...

Researchers successfully clone adult human stem cells

Apr 18, 2014

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

User comments : 0

More news stories

Biologists help solve fungi mysteries

(Phys.org) —A new genetic analysis revealing the previously unknown biodiversity and distribution of thousands of fungi in North America might also reveal a previously underappreciated contributor to climate ...

Making graphene in your kitchen

Graphene has been touted as a wonder material—the world's thinnest substance, but super-strong. Now scientists say it is so easy to make you could produce some in your kitchen.