Migration of bacteria to the edges of the colony under ultraviolet radiation (original) (raw)

2001

Abstract

ABSTRACT Living organisms exhibit remarkable cooperative behavior in response to environmental stress. Bacterial colonies growing on a nutrient-rich substrate have served as model systems for studying pattern formation and population dynamics in biological systems. We report a novel spatio-temporal response of a Bacillus subtilis colony initially growing under ambient conditions to ultraviolet (UV) radiation exposure. The growth of the colonies decreased, but remarkably, the bacteria at the center of the colonies migrated towards the colony edge forming a ring during uniform exposure. The migration of the bacteria has no obvious benefit since they are still under UV radiation of the same strength. When the radiation is switched off, the colonies were observed to grow both inward into the evacuated regions as well as outward indicating that the pattern is not a swarming ring formed due to depletion of nutrients at the center of the colony. We also discuss the results of directed random walk simulations. Using simple models we show the rearrangement is not a consequence of linear attraction or repulsion between the bacteria.

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