Researchers develop technique for bacteria crowd control

April 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: System holds promise for study of biological systems, biosensors and bio-hybrid devices

Related Stories

How cranberries impact infection-causing bacteria

July 15, 2013

Consuming cranberry products has been anecdotally associated with prevention of urinary tract infections (UTIs) for over 100 years. But is this popular belief a myth, or scientific fact?

Microorganisms act as tiny machines in future MEMS devices

April 26, 2007

The single-celled Spirostomum is a tiny brown worm that can contract its 500-micrometer-long body to 25% of its length in a millisecond, making this protozoan the fastest-contracting microorganism known. Scientists think ...

Recommended for you

Facts, beliefs, and identity: The seeds of science skepticism

January 22, 2017

Psychological researchers are working to understand the cognitive processes, ideologies, cultural demands, and conspiracy beliefs that cause smart people to resist scientific messages. Using surveys, experiments, observational ...

'Droneboarding' takes off in Latvia

January 22, 2017

Skirted on all sides by snow-clad pine forests, Latvia's remote Lake Ninieris would be the perfect picture of winter tranquility—were it not for the huge drone buzzing like a swarm of angry bees as it zooms above the solid ...

Singapore 2G switchoff highlights digital divide

January 22, 2017

When Singapore pulls the plug on its 2G mobile phone network this year, thousands of people could be stuck without a signal—digital have-nots left behind by the relentless march of technology.

Freeze-dried food and 1 bathroom: 6 simulate Mars in dome

January 20, 2017

Crammed into a dome with one bathroom, six scientists will spend eight months munching on mostly freeze-dried foods—with a rare treat of Spam—and have only their small sleeping quarters to retreat to for solace.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.