Evaluation of Xanthomonas campestris survival in a soil microcosm system

Xanthomonas campestris pv. campestris is a pathogen of cruciferous plants. We studied the survival of the wild type strain and mutant derivatives which are deficient in exopolysaccharide (EPS) or in extracellular protease synthesis in soil microcosms in order to test the hypothesis that, in this environment, adherence to soil particles and scavenging of nutrients are very important strategies for bacterial survival. In sterile soil microcosms, differences in survival were only observed between the EPS producer and its mutant. In non-sterile soil experiments, survival of Prt- mutant was similar to EPS- mutant, suggesting that both characteristics have a strong influence in survival in the presence of the natural bacterial community. Bacterial decrease represented by the slope of regression lines was higher in non-sterile soil microcosms due to the influence of biotic interactions.