Ravenous but a remedy all right

Famished bacteria are now known to be able to enter porous media like soil and create a bio-barrier to prevent the spread of pollutants

Published: Tuesday 15 October 1996

Ultramicrobacteria(white strea when certain forms of bacteria are subjected to starvation they are rendered fit to penetrate contaminated media whose surfacial pores would otherwise be too small for their size. Reaching the undersurface, shrunk bacteria resuscitate and accomplish a task hitherto unthought of. They create a barrier between the contaminated stretches of the medium and the rest of it so that the pollutant does not diffuse further. This property of the bacteria to create a 'bio-barrier' is being exploited by scientists to treat heavy metal contamination underground ( Environmental Science and Technology , Vol 30, No 8).

The loss of girth earns the bacteria the name "ultramicrobacteria". Researchers at the Montana State University in the us, under the direction of J William Costerton, are busy producing ultramicrobacteria in the laboratory. According to them, the bacteria which are normally about one micron (a micron is one-millionth of a metre) in length, decrease to about 0.3 micron on starvation and become more spherical. After entering the porous substrate, these bacteria are back to their normal size in less than two days.

Currently undergoing largescale laboratory trials, the bio-barrier technology uses those strains of bacteria which are devoid of the spore-forming ability. Since spore-forming bacteria become dormant cells covered by a protein coat when stressed, their use for the purpose is ruled out. On the other hand, non spore-forming bacteria retain their vitality even on starvation. The bacteria can be used in chromium or radionuclide-contaminated soil for bioremediation. Bioremediation refers to a technique wherein organisms are used to remove pollutants from the soil. The study has shown that the shewanella strain of bacteria can change to the ultramicro form and then revived.

The research is being funded by the us department of energy and mse Incorporated, an engineering and environmental consulting company in Montana.

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