GENERIC MODELING OF COOPERATIVE GROWTH-PATTERNS IN BACTERIAL COLONIES

BACTERIAL colonies must often cope with unfavourable environmental con ditions(1,2). To do so, they have developed sophisticated modes of coo perative behaviour(3-10). It has been found that such behaviour can ca use bacterial colonies to exhibit complex growth patterns similar to t hose observed during non-equilibrium growth processes in non-living sy stems(11) some of the qualitative features of the latter may be invoke d to account for the complex patterns of bacterial growth(12-18). Here we show that a simple model of bacterial growth can reproduce the sal ient features of the observed growth patterns. The model incorporates random walkers, representing aggregates of bacteria, which move in res ponse to gradients in nutrient concentration and communicate with each other by means of chemotactic 'feedback'. These simple features allow the colony to respond efficiently to adverse growth conditions, and g enerate self-organization over a wide range of length scales.