Bacterial cooperative organization under antibiotic stress

Bacteria have developed sophisticated modes of cooperative behavior to cope with unfavorable environmental conditions. Here we report the e ect of antibiotic stress on the colonial development of Paenibacillus dendritiformis and P. vortex. We focus on the e ect of co-trimoxazole on the colonial organization of P. dendritiformis. We nd that the exposure to non-lethal concentrations of antibiotic leads to dramatic changes in the colonial growth patterns. Branching, tip-splitting patterns are a ected by reduction in the colonial fractal dimension from Df =2:0 to 1:7, appearance of pronounced weak chirality and pronounced radial orientation of the growth. We combine the experimental observations with numerical studies of both discrete and continuous generic models to reveal the causes for the modi cations in the patterns. We conclude that the bacteria adjust their chemotactic signaling together with variations in the bacteria length and increase in the metabolic load. c © 2000 Elsevier Science B.V. All rights reserved.