Bacterial cells contain a number of receptors and each one affects a particular behaviour or trait -- for example, where to move or even to become more virulent.

What has remained unknow is how individual receptors, by sensing their environment, directly affect a bacterium's behaviour and ability to adapt to its environment.

Gladys Alexandre -- an associate professor of biochemistry, cellular and molecular biology at the University of Tennessee at Knoxville -- is one of the first to isolate and study a receptor in this way.

Biologist normally study the common bacteria Escherichia coli as the model for bacteria's ability to move actively and independently.

But Professor Alexandre decided to look at the more complex soil bacterium, Azospirillum brasilense.

"As bacteria's ability to make decisions goes, E. coli is kind of dumb, which makes it easy for researchers to study sensing and information processing -- essentially, decision making -- in this bacterium," she said.

A. brasilense has 48 receptors versus as opposed to the five receptors generally found in E. coli.

Professor Alexandre and her colleagues homed in on a receptor that they suspected was involved in nitrogen fixing -- the biological process that turns atmospheric nitrogen gas into ammonium, a process that makes it available for metabolisation by other organisms.

But the exact biological processes involved were still unclear -- so Professor Alexandre turned to a colleague using the latest computer-based techniques for analysing genetic structures.

Igor Jouline of Oak Ridge National Laboratory was able to generate a model of the receptor's structure and compared it to other known structures on a nearly atom-by-atom basis.

This enabled them to predict which one of the more than 100 amino acids in the sensory part of the receptor is responsible for sensing the precise oxygen concentration that the bacterium needs for nitrogen fixing.

Using conventional genetic techniques, this would have taken a significant amount of time -- but using computers made the process much quicker.

"Partnering with Igor provided us great insight," said Professor Alexandre.

"We would not have been able to fully understand how this receptor works without him."

"We see now that bacteria are, in their way, big thinkers, and by knowing how they 'feel' about the environment around them, we can look at new and different ways to work with them."