Bacteria shun the limelight

Abstract

Scientists at Clark University (Worcester, MA, USA) have found that bacterial colonies irradiated with UV light will migrate to form large ring-shaped patterns thus indicating that stress caused by UV exposure is having an effect on the bacteria's metabolism (Physics Review Letters, 8 October). Cultures of the soil bacterium Bacillus subtilisin grown on a nutrient-rich medium were exposed to a uniform UV light, and began to migrate away from the centre of the original colony. When the light was turned off, the bacteria repopulated the areas that had been vacated. The Clark team propose that UV-induced stress causes the bacteria to become sensitised to waste metabolites that accumulate at the colony centre, and that cells at the colony's edge emit chemicals to attract the others to regions of uncontaminated media. These results could have implications for understanding the effects of UV exposure on biological systems due to depletion of the ozone layer. MJD