In the News
Swarming ring patterns in bacterial colonies exposed to ultraviolet radiation, published in Physical Review Letters, 87, 158102 (2001) was cited in:
Physics News Update, October 3, 2001
The Boston Globe, October 23, 2001
The Physics News Graphics, October 23 2001
The New Scientist, October 20, 2001
Biological pattern formation
We have observed a novel morphological transition in a Bacillus subtilis colony initially growing under ambient conditions, after ultraviolet radiation exposure. The bacteria in the central regions of the colonies are observed to migrate towards the colony edge forming a ring during uniform spatial exposure. When the radiation is switched off, the colonies were observed to grow inward into the evacuated regions as well as outward indicating that the pattern is not formed due to depletion of nutrients at the center of the colony. We also propose a reaction-diffusion model in which waste-limited chemotaxis initiated by the UV radiation leads to the observed phenomenology.
The migration of life in response to a changing environment is a common theme in biological systems. The change in environment may be due to global warming, ground water changes, forest fires or could be as simple action of wind on sand dunes.
In the White Sands National Monument the Soaptree Yucca grows up to a foot a year to keep its leaves above the slowly marching sand.