Micro-organisms can detect minute changes in their environment

How they detect minute changes in their environment

Published: Saturday 15 July 2006

-- scientists have known that bacteria possess the ability to sense minute changes in their environment. But they didn't know how micro-organisms did this. Researchers at Cornell University, usa, say they have found the answer -- germs are able to amplify their senses.

Explaining the mechanism, the researchers say that bacteria pick up information about their surroundings through compounds called receptors. Rows of receptors are found on the surface of their microscopic forms. The researchers hypothesised that the receptors are linked through enzymes, enabling them to operate as a cooperative lattice, implying that a change in one will be reflected in the entire lattice.

Using a combination of x -ray crystallography to determine the structure of receptors and enzymes and a novel spectroscopic technique -- pulsed electron spin resonance dipolar spectroscopy -- to measure interactions between them, researchers developed a model to show the organisation of receptors. "When one receptor detects, for example, a sugar molecule in its environment, communication of some sort triggers an array of linked receptors to rearrange itself, much like when water freezes, all the water molecules assort themselves into a new structure," says Brian Crane, a co-author.

A reorganisation of receptors enables bacteria to amplify the signal that a specific molecule has been sensed outside the cell. The same enzymes again get activated, allowing the bacteria to move closer to or away from what it has sensed. The mechanism allows the microbes to detect changes as small as 0.1 per cent, or one part in a 1,000, in their environment. The study was published in the journal, Nature Structural and Molecular Biology (Vol 13, No 5, May 2006).

Experts believe that it is probably because of this property that bacteria are able to adapt quickly to change. Researchers believe that a better understanding of the process may lead to developing useful molecular devices to sense a wide range of chemicals, light, p h (to measure acidity/alkalinity of a liquid) and heavy metals with higher sensitivity.

It may even be possible to engineer bacteria that respond to stimuli such as pollutants or explosives.

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